Paper/patches/server/0016-Starlight.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Wed, 28 Oct 2020 16:51:55 -0700
Subject: [PATCH] Starlight

See https://github.com/PaperMC/Starlight

== AT ==
public net.minecraft.server.level.ChunkHolder broadcast(Lnet/minecraft/network/protocol/Packet;Z)V
public net.minecraft.world.level.chunk.LevelChunkSection states

diff --git a/src/main/java/ca/spottedleaf/starlight/common/light/BlockStarLightEngine.java b/src/main/java/ca/spottedleaf/starlight/common/light/BlockStarLightEngine.java
new file mode 100644
index 0000000000000000000000000000000000000000..09ddbbfdf656aa347830941abd7c994fac05d1c5
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/starlight/common/light/BlockStarLightEngine.java
@@ -0,0 +1,279 @@
+package ca.spottedleaf.starlight.common.light;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkStatus;
+import net.minecraft.world.level.chunk.ImposterProtoChunk;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.world.level.chunk.LightChunkGetter;
+import net.minecraft.world.level.chunk.PalettedContainer;
+import net.minecraft.world.phys.shapes.Shapes;
+import net.minecraft.world.phys.shapes.VoxelShape;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+public final class BlockStarLightEngine extends StarLightEngine {
+
+    public BlockStarLightEngine(final Level world) {
+        super(false, world);
+    }
+
+    @Override
+    protected boolean[] getEmptinessMap(final ChunkAccess chunk) {
+        return chunk.getBlockEmptinessMap();
+    }
+
+    @Override
+    protected void setEmptinessMap(final ChunkAccess chunk, final boolean[] to) {
+        chunk.setBlockEmptinessMap(to);
+    }
+
+    @Override
+    protected SWMRNibbleArray[] getNibblesOnChunk(final ChunkAccess chunk) {
+        return chunk.getBlockNibbles();
+    }
+
+    @Override
+    protected void setNibbles(final ChunkAccess chunk, final SWMRNibbleArray[] to) {
+        chunk.setBlockNibbles(to);
+    }
+
+    @Override
+    protected boolean canUseChunk(final ChunkAccess chunk) {
+        return chunk.getStatus().isOrAfter(ChunkStatus.LIGHT) && (this.isClientSide || chunk.isLightCorrect());
+    }
+
+    @Override
+    protected void setNibbleNull(final int chunkX, final int chunkY, final int chunkZ) {
+        final SWMRNibbleArray nibble = this.getNibbleFromCache(chunkX, chunkY, chunkZ);
+        if (nibble != null) {
+            // de-initialisation is not as straightforward as with sky data, since deinit of block light is typically
+            // because a block was removed - which can decrease light. with sky data, block breaking can only result
+            // in increases, and thus the existing sky block check will actually correctly propagate light through
+            // a null section. so in order to propagate decreases correctly, we can do a couple of things: not remove
+            // the data section, or do edge checks on ALL axis (x, y, z). however I do not want edge checks running
+            // for clients at all, as they are expensive. so we don't remove the section, but to maintain the appearence
+            // of vanilla data management we "hide" them.
+            nibble.setHidden();
+        }
+    }
+
+    @Override
+    protected void initNibble(final int chunkX, final int chunkY, final int chunkZ, final boolean extrude, final boolean initRemovedNibbles) {
+        if (chunkY < this.minLightSection || chunkY > this.maxLightSection || this.getChunkInCache(chunkX, chunkZ) == null) {
+            return;
+        }
+
+        final SWMRNibbleArray nibble = this.getNibbleFromCache(chunkX, chunkY, chunkZ);
+        if (nibble == null) {
+            if (!initRemovedNibbles) {
+                throw new IllegalStateException();
+            } else {
+                this.setNibbleInCache(chunkX, chunkY, chunkZ, new SWMRNibbleArray());
+            }
+        } else {
+            nibble.setNonNull();
+        }
+    }
+
+    @Override
+    protected final void checkBlock(final LightChunkGetter lightAccess, final int worldX, final int worldY, final int worldZ) {
+        // blocks can change opacity
+        // blocks can change emitted light
+        // blocks can change direction of propagation
+
+        final int encodeOffset = this.coordinateOffset;
+        final int emittedMask = this.emittedLightMask;
+
+        final int currentLevel = this.getLightLevel(worldX, worldY, worldZ);
+        final BlockState blockState = this.getBlockState(worldX, worldY, worldZ);
+        final int emittedLevel = blockState.getLightEmission() & emittedMask;
+
+        this.setLightLevel(worldX, worldY, worldZ, emittedLevel);
+        // this accounts for change in emitted light that would cause an increase
+        if (emittedLevel != 0) {
+            this.appendToIncreaseQueue(
+                    ((worldX + (worldZ << 6) + (worldY << (6 + 6)) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                            | (emittedLevel & 0xFL) << (6 + 6 + 16)
+                            | (((long)ALL_DIRECTIONS_BITSET) << (6 + 6 + 16 + 4))
+                            | (blockState.isConditionallyFullOpaque() ? FLAG_HAS_SIDED_TRANSPARENT_BLOCKS : 0)
+            );
+        }
+        // this also accounts for a change in emitted light that would cause a decrease
+        // this also accounts for the change of direction of propagation (i.e old block was full transparent, new block is full opaque or vice versa)
+        // as it checks all neighbours (even if current level is 0)
+        this.appendToDecreaseQueue(
+                ((worldX + (worldZ << 6) + (worldY << (6 + 6)) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                        | (currentLevel & 0xFL) << (6 + 6 + 16)
+                        | (((long)ALL_DIRECTIONS_BITSET) << (6 + 6 + 16 + 4))
+                        // always keep sided transparent false here, new block might be conditionally transparent which would
+                        // prevent us from decreasing sources in the directions where the new block is opaque
+                        // if it turns out we were wrong to de-propagate the source, the re-propagate logic WILL always
+                        // catch that and fix it.
+        );
+        // re-propagating neighbours (done by the decrease queue) will also account for opacity changes in this block
+    }
+
+    protected final BlockPos.MutableBlockPos recalcCenterPos = new BlockPos.MutableBlockPos();
+    protected final BlockPos.MutableBlockPos recalcNeighbourPos = new BlockPos.MutableBlockPos();
+
+    @Override
+    protected int calculateLightValue(final LightChunkGetter lightAccess, final int worldX, final int worldY, final int worldZ,
+                                      final int expect) {
+        final BlockState centerState = this.getBlockState(worldX, worldY, worldZ);
+        int level = centerState.getLightEmission() & 0xF;
+
+        if (level >= (15 - 1) || level > expect) {
+            return level;
+        }
+
+        final int sectionOffset = this.chunkSectionIndexOffset;
+        final BlockState conditionallyOpaqueState;
+        int opacity = centerState.getOpacityIfCached();
+
+        if (opacity == -1) {
+            this.recalcCenterPos.set(worldX, worldY, worldZ);
+            opacity = centerState.getLightBlock(lightAccess.getLevel(), this.recalcCenterPos);
+            if (centerState.isConditionallyFullOpaque()) {
+                conditionallyOpaqueState = centerState;
+            } else {
+                conditionallyOpaqueState = null;
+            }
+        } else if (opacity >= 15) {
+            return level;
+        } else {
+            conditionallyOpaqueState = null;
+        }
+        opacity = Math.max(1, opacity);
+
+        for (final AxisDirection direction : AXIS_DIRECTIONS) {
+            final int offX = worldX + direction.x;
+            final int offY = worldY + direction.y;
+            final int offZ = worldZ + direction.z;
+
+            final int sectionIndex = (offX >> 4) + 5 * (offZ >> 4) + (5 * 5) * (offY >> 4) + sectionOffset;
+
+            final int neighbourLevel = this.getLightLevel(sectionIndex, (offX & 15) | ((offZ & 15) << 4) | ((offY & 15) << 8));
+
+            if ((neighbourLevel - 1) <= level) {
+                // don't need to test transparency, we know it wont affect the result.
+                continue;
+            }
+
+            final BlockState neighbourState = this.getBlockState(offX, offY, offZ);
+            if (neighbourState.isConditionallyFullOpaque()) {
+                // here the block can be conditionally opaque (i.e light cannot propagate from it), so we need to test that
+                // we don't read the blockstate because most of the time this is false, so using the faster
+                // known transparency lookup results in a net win
+                this.recalcNeighbourPos.set(offX, offY, offZ);
+                final VoxelShape neighbourFace = neighbourState.getFaceOcclusionShape(lightAccess.getLevel(), this.recalcNeighbourPos, direction.opposite.nms);
+                final VoxelShape thisFace = conditionallyOpaqueState == null ? Shapes.empty() : conditionallyOpaqueState.getFaceOcclusionShape(lightAccess.getLevel(), this.recalcCenterPos, direction.nms);
+                if (Shapes.faceShapeOccludes(thisFace, neighbourFace)) {
+                    // not allowed to propagate
+                    continue;
+                }
+            }
+
+            // passed transparency,
+
+            final int calculated = neighbourLevel - opacity;
+            level = Math.max(calculated, level);
+            if (level > expect) {
+                return level;
+            }
+        }
+
+        return level;
+    }
+
+    @Override
+    protected void propagateBlockChanges(final LightChunkGetter lightAccess, final ChunkAccess atChunk, final Set<BlockPos> positions) {
+        for (final BlockPos pos : positions) {
+            this.checkBlock(lightAccess, pos.getX(), pos.getY(), pos.getZ());
+        }
+
+        this.performLightDecrease(lightAccess);
+    }
+
+    protected List<BlockPos> getSources(final LightChunkGetter lightAccess, final ChunkAccess chunk) {
+        final List<BlockPos> sources = new ArrayList<>();
+
+        final int offX = chunk.getPos().x << 4;
+        final int offZ = chunk.getPos().z << 4;
+
+        final LevelChunkSection[] sections = chunk.getSections();
+        for (int sectionY = this.minSection; sectionY <= this.maxSection; ++sectionY) {
+            final LevelChunkSection section = sections[sectionY - this.minSection];
+            if (section == null || section.hasOnlyAir()) {
+                // no sources in empty sections
+                continue;
+            }
+            if (!section.maybeHas((final BlockState state) -> {
+                return state.getLightEmission() > 0;
+            })) {
+                // no light sources in palette
+                continue;
+            }
+            final PalettedContainer<BlockState> states = section.states;
+            final int offY = sectionY << 4;
+
+            for (int index = 0; index < (16 * 16 * 16); ++index) {
+                final BlockState state = states.get(index);
+                if (state.getLightEmission() <= 0) {
+                    continue;
+                }
+
+                // index = x | (z << 4) | (y << 8)
+                sources.add(new BlockPos(offX | (index & 15), offY | (index >>> 8), offZ | ((index >>> 4) & 15)));
+            }
+        }
+
+        return sources;
+    }
+
+    @Override
+    public void lightChunk(final LightChunkGetter lightAccess, final ChunkAccess chunk, final boolean needsEdgeChecks) {
+        // setup sources
+        final int emittedMask = this.emittedLightMask;
+        final List<BlockPos> positions = this.getSources(lightAccess, chunk);
+        for (int i = 0, len = positions.size(); i < len; ++i) {
+            final BlockPos pos = positions.get(i);
+            final BlockState blockState = this.getBlockState(pos.getX(), pos.getY(), pos.getZ());
+            final int emittedLight = blockState.getLightEmission() & emittedMask;
+
+            if (emittedLight <= this.getLightLevel(pos.getX(), pos.getY(), pos.getZ())) {
+                // some other source is brighter
+                continue;
+            }
+
+            this.appendToIncreaseQueue(
+                    ((pos.getX() + (pos.getZ() << 6) + (pos.getY() << (6 + 6)) + this.coordinateOffset) & ((1L << (6 + 6 + 16)) - 1))
+                            | (emittedLight & 0xFL) << (6 + 6 + 16)
+                            | (((long)ALL_DIRECTIONS_BITSET) << (6 + 6 + 16 + 4))
+                            | (blockState.isConditionallyFullOpaque() ? FLAG_HAS_SIDED_TRANSPARENT_BLOCKS : 0)
+            );
+
+
+            // propagation wont set this for us
+            this.setLightLevel(pos.getX(), pos.getY(), pos.getZ(), emittedLight);
+        }
+
+        if (needsEdgeChecks) {
+            // not required to propagate here, but this will reduce the hit of the edge checks
+            this.performLightIncrease(lightAccess);
+
+            // verify neighbour edges
+            this.checkChunkEdges(lightAccess, chunk, this.minLightSection, this.maxLightSection);
+        } else {
+            this.propagateNeighbourLevels(lightAccess, chunk, this.minLightSection, this.maxLightSection);
+
+            this.performLightIncrease(lightAccess);
+        }
+    }
+}
diff --git a/src/main/java/ca/spottedleaf/starlight/common/light/SWMRNibbleArray.java b/src/main/java/ca/spottedleaf/starlight/common/light/SWMRNibbleArray.java
new file mode 100644
index 0000000000000000000000000000000000000000..4ffb4ffe01c4628d52742c5c0bbd35220eea6294
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/starlight/common/light/SWMRNibbleArray.java
@@ -0,0 +1,440 @@
+package ca.spottedleaf.starlight.common.light;
+
+import net.minecraft.world.level.chunk.DataLayer;
+import java.util.ArrayDeque;
+import java.util.Arrays;
+
+// SWMR -> Single Writer Multi Reader Nibble Array
+public final class SWMRNibbleArray {
+
+    /*
+     * Null nibble - nibble does not exist, and should not be written to. Just like vanilla - null
+     * nibbles are always 0 - and they are never written to directly. Only initialised/uninitialised
+     * nibbles can be written to.
+     *
+     * Uninitialised nibble - They are all 0, but the backing array isn't initialised.
+     *
+     * Initialised nibble - Has light data.
+     */
+
+    protected static final int INIT_STATE_NULL   = 0; // null
+    protected static final int INIT_STATE_UNINIT = 1; // uninitialised
+    protected static final int INIT_STATE_INIT   = 2; // initialised
+    protected static final int INIT_STATE_HIDDEN = 3; // initialised, but conversion to Vanilla data should be treated as if NULL
+
+    public static final int ARRAY_SIZE = 16 * 16 * 16 / (8/4); // blocks / bytes per block
+    // this allows us to maintain only 1 byte array when we're not updating
+    static final ThreadLocal<ArrayDeque<byte[]>> WORKING_BYTES_POOL = ThreadLocal.withInitial(ArrayDeque::new);
+
+    private static byte[] allocateBytes() {
+        final byte[] inPool = WORKING_BYTES_POOL.get().pollFirst();
+        if (inPool != null) {
+            return inPool;
+        }
+
+        return new byte[ARRAY_SIZE];
+    }
+
+    private static void freeBytes(final byte[] bytes) {
+        WORKING_BYTES_POOL.get().addFirst(bytes);
+    }
+
+    public static SWMRNibbleArray fromVanilla(final DataLayer nibble) {
+        if (nibble == null) {
+            return new SWMRNibbleArray(null, true);
+        } else if (nibble.isEmpty()) {
+            return new SWMRNibbleArray();
+        } else {
+            return new SWMRNibbleArray(nibble.getData().clone()); // make sure we don't write to the parameter later
+        }
+    }
+
+    protected int stateUpdating;
+    protected volatile int stateVisible;
+
+    protected byte[] storageUpdating;
+    protected boolean updatingDirty; // only returns whether storageUpdating is dirty
+    protected volatile byte[] storageVisible;
+
+    public SWMRNibbleArray() {
+        this(null, false); // lazy init
+    }
+
+    public SWMRNibbleArray(final byte[] bytes) {
+        this(bytes, false);
+    }
+
+    public SWMRNibbleArray(final byte[] bytes, final boolean isNullNibble) {
+        if (bytes != null && bytes.length != ARRAY_SIZE) {
+            throw new IllegalArgumentException("Data of wrong length: " + bytes.length);
+        }
+        this.stateVisible = this.stateUpdating = bytes == null ? (isNullNibble ? INIT_STATE_NULL : INIT_STATE_UNINIT) : INIT_STATE_INIT;
+        this.storageUpdating = this.storageVisible = bytes;
+    }
+
+    public SWMRNibbleArray(final byte[] bytes, final int state) {
+        if (bytes != null && bytes.length != ARRAY_SIZE) {
+            throw new IllegalArgumentException("Data of wrong length: " + bytes.length);
+        }
+        if (bytes == null && (state == INIT_STATE_INIT || state == INIT_STATE_HIDDEN)) {
+            throw new IllegalArgumentException("Data cannot be null and have state be initialised");
+        }
+        this.stateUpdating = this.stateVisible = state;
+        this.storageUpdating = this.storageVisible = bytes;
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder stringBuilder = new StringBuilder();
+        stringBuilder.append("State: ");
+        switch (this.stateVisible) {
+            case INIT_STATE_NULL:
+                stringBuilder.append("null");
+                break;
+            case INIT_STATE_UNINIT:
+                stringBuilder.append("uninitialised");
+                break;
+            case INIT_STATE_INIT:
+                stringBuilder.append("initialised");
+                break;
+            case INIT_STATE_HIDDEN:
+                stringBuilder.append("hidden");
+                break;
+            default:
+                stringBuilder.append("unknown");
+                break;
+        }
+        stringBuilder.append("\nData:\n");
+
+        final byte[] data = this.storageVisible;
+        if (data != null) {
+            for (int i = 0; i < 4096; ++i) {
+                // Copied from NibbleArray#toString
+                final int level = ((data[i >>> 1] >>> ((i & 1) << 2)) & 0xF);
+
+                stringBuilder.append(Integer.toHexString(level));
+                if ((i & 15) == 15) {
+                    stringBuilder.append("\n");
+                }
+
+                if ((i & 255) == 255) {
+                    stringBuilder.append("\n");
+                }
+            }
+        } else {
+            stringBuilder.append("null");
+        }
+
+        return stringBuilder.toString();
+    }
+
+    public SaveState getSaveState() {
+        synchronized (this) {
+            final int state = this.stateVisible;
+            final byte[] data = this.storageVisible;
+            if (state == INIT_STATE_NULL) {
+                return null;
+            }
+            if (state == INIT_STATE_UNINIT) {
+                return new SaveState(null, state);
+            }
+            final boolean zero = isAllZero(data);
+            if (zero) {
+                return state == INIT_STATE_INIT ? new SaveState(null, INIT_STATE_UNINIT) : null;
+            } else {
+                return new SaveState(data.clone(), state);
+            }
+        }
+    }
+
+    protected static boolean isAllZero(final byte[] data) {
+        for (int i = 0; i < (ARRAY_SIZE >>> 4); ++i) {
+            byte whole = data[i << 4];
+
+            for (int k = 1; k < (1 << 4); ++k) {
+                whole |= data[(i << 4) | k];
+            }
+
+            if (whole != 0) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    // operation type: updating on src, updating on other
+    public void extrudeLower(final SWMRNibbleArray other) {
+        if (other.stateUpdating == INIT_STATE_NULL) {
+            throw new IllegalArgumentException();
+        }
+
+        if (other.storageUpdating == null) {
+            this.setUninitialised();
+            return;
+        }
+
+        final byte[] src = other.storageUpdating;
+        final byte[] into;
+
+        if (!this.updatingDirty) {
+            if (this.storageUpdating != null) {
+                into = this.storageUpdating = allocateBytes();
+            } else {
+                this.storageUpdating = into = allocateBytes();
+                this.stateUpdating = INIT_STATE_INIT;
+            }
+            this.updatingDirty = true;
+        } else {
+            into = this.storageUpdating;
+        }
+
+        final int start = 0;
+        final int end = (15 | (15 << 4)) >>> 1;
+
+        /* x | (z << 4) | (y << 8) */
+        for (int y = 0; y <= 15; ++y) {
+            System.arraycopy(src, start, into, y << (8 - 1), end - start + 1);
+        }
+    }
+
+    // operation type: updating
+    public void setFull() {
+        if (this.stateUpdating != INIT_STATE_HIDDEN) {
+            this.stateUpdating = INIT_STATE_INIT;
+        }
+        Arrays.fill(this.storageUpdating == null || !this.updatingDirty ? this.storageUpdating = allocateBytes() : this.storageUpdating, (byte)-1);
+        this.updatingDirty = true;
+    }
+
+    // operation type: updating
+    public void setZero() {
+        if (this.stateUpdating != INIT_STATE_HIDDEN) {
+            this.stateUpdating = INIT_STATE_INIT;
+        }
+        Arrays.fill(this.storageUpdating == null || !this.updatingDirty ? this.storageUpdating = allocateBytes() : this.storageUpdating, (byte)0);
+        this.updatingDirty = true;
+    }
+
+    // operation type: updating
+    public void setNonNull() {
+        if (this.stateUpdating == INIT_STATE_HIDDEN) {
+            this.stateUpdating = INIT_STATE_INIT;
+            return;
+        }
+        if (this.stateUpdating != INIT_STATE_NULL) {
+            return;
+        }
+        this.stateUpdating = INIT_STATE_UNINIT;
+    }
+
+    // operation type: updating
+    public void setNull() {
+        this.stateUpdating = INIT_STATE_NULL;
+        if (this.updatingDirty && this.storageUpdating != null) {
+            freeBytes(this.storageUpdating);
+        }
+        this.storageUpdating = null;
+        this.updatingDirty = false;
+    }
+
+    // operation type: updating
+    public void setUninitialised() {
+        this.stateUpdating = INIT_STATE_UNINIT;
+        if (this.storageUpdating != null && this.updatingDirty) {
+            freeBytes(this.storageUpdating);
+        }
+        this.storageUpdating = null;
+        this.updatingDirty = false;
+    }
+
+    // operation type: updating
+    public void setHidden() {
+        if (this.stateUpdating == INIT_STATE_HIDDEN) {
+            return;
+        }
+        if (this.stateUpdating != INIT_STATE_INIT) {
+            this.setNull();
+        } else {
+            this.stateUpdating = INIT_STATE_HIDDEN;
+        }
+    }
+
+    // operation type: updating
+    public boolean isDirty() {
+        return this.stateUpdating != this.stateVisible || this.updatingDirty;
+    }
+
+    // operation type: updating
+    public boolean isNullNibbleUpdating() {
+        return this.stateUpdating == INIT_STATE_NULL;
+    }
+
+    // operation type: visible
+    public boolean isNullNibbleVisible() {
+        return this.stateVisible == INIT_STATE_NULL;
+    }
+
+    // opeartion type: updating
+    public boolean isUninitialisedUpdating() {
+        return this.stateUpdating == INIT_STATE_UNINIT;
+    }
+
+    // operation type: visible
+    public boolean isUninitialisedVisible() {
+        return this.stateVisible == INIT_STATE_UNINIT;
+    }
+
+    // operation type: updating
+    public boolean isInitialisedUpdating() {
+        return this.stateUpdating == INIT_STATE_INIT;
+    }
+
+    // operation type: visible
+    public boolean isInitialisedVisible() {
+        return this.stateVisible == INIT_STATE_INIT;
+    }
+
+    // operation type: updating
+    public boolean isHiddenUpdating() {
+        return this.stateUpdating == INIT_STATE_HIDDEN;
+    }
+
+    // operation type: updating
+    public boolean isHiddenVisible() {
+        return this.stateVisible == INIT_STATE_HIDDEN;
+    }
+
+    // operation type: updating
+    protected void swapUpdatingAndMarkDirty() {
+        if (this.updatingDirty) {
+            return;
+        }
+
+        if (this.storageUpdating == null) {
+            this.storageUpdating = allocateBytes();
+            Arrays.fill(this.storageUpdating, (byte)0);
+        } else {
+            System.arraycopy(this.storageUpdating, 0, this.storageUpdating = allocateBytes(), 0, ARRAY_SIZE);
+        }
+
+        if (this.stateUpdating != INIT_STATE_HIDDEN) {
+            this.stateUpdating = INIT_STATE_INIT;
+        }
+        this.updatingDirty = true;
+    }
+
+    // operation type: updating
+    public boolean updateVisible() {
+        if (!this.isDirty()) {
+            return false;
+        }
+
+        synchronized (this) {
+            if (this.stateUpdating == INIT_STATE_NULL || this.stateUpdating == INIT_STATE_UNINIT) {
+                this.storageVisible = null;
+            } else {
+                if (this.storageVisible == null) {
+                    this.storageVisible = this.storageUpdating.clone();
+                } else {
+                    if (this.storageUpdating != this.storageVisible) {
+                        System.arraycopy(this.storageUpdating, 0, this.storageVisible, 0, ARRAY_SIZE);
+                    }
+                }
+
+                if (this.storageUpdating != this.storageVisible) {
+                    freeBytes(this.storageUpdating);
+                }
+                this.storageUpdating = this.storageVisible;
+            }
+            this.updatingDirty = false;
+            this.stateVisible = this.stateUpdating;
+        }
+
+        return true;
+    }
+
+    // operation type: visible
+    public DataLayer toVanillaNibble() {
+        synchronized (this) {
+            switch (this.stateVisible) {
+                case INIT_STATE_HIDDEN:
+                case INIT_STATE_NULL:
+                    return null;
+                case INIT_STATE_UNINIT:
+                    return new DataLayer();
+                case INIT_STATE_INIT:
+                    return new DataLayer(this.storageVisible.clone());
+                default:
+                    throw new IllegalStateException();
+            }
+        }
+    }
+
+    /* x | (z << 4) | (y << 8) */
+
+    // operation type: updating
+    public int getUpdating(final int x, final int y, final int z) {
+        return this.getUpdating((x & 15) | ((z & 15) << 4) | ((y & 15) << 8));
+    }
+
+    // operation type: updating
+    public int getUpdating(final int index) {
+        // indices range from 0 -> 4096
+        final byte[] bytes = this.storageUpdating;
+        if (bytes == null) {
+            return 0;
+        }
+        final byte value = bytes[index >>> 1];
+
+        // if we are an even index, we want lower 4 bits
+        // if we are an odd index, we want upper 4 bits
+        return ((value >>> ((index & 1) << 2)) & 0xF);
+    }
+
+    // operation type: visible
+    public int getVisible(final int x, final int y, final int z) {
+        return this.getVisible((x & 15) | ((z & 15) << 4) | ((y & 15) << 8));
+    }
+
+    // operation type: visible
+    public int getVisible(final int index) {
+        // indices range from 0 -> 4096
+        final byte[] visibleBytes = this.storageVisible;
+        if (visibleBytes == null) {
+            return 0;
+        }
+        final byte value = visibleBytes[index >>> 1];
+
+        // if we are an even index, we want lower 4 bits
+        // if we are an odd index, we want upper 4 bits
+        return ((value >>> ((index & 1) << 2)) & 0xF);
+    }
+
+    // operation type: updating
+    public void set(final int x, final int y, final int z, final int value) {
+        this.set((x & 15) | ((z & 15) << 4) | ((y & 15) << 8), value);
+    }
+
+    // operation type: updating
+    public void set(final int index, final int value) {
+        if (!this.updatingDirty) {
+            this.swapUpdatingAndMarkDirty();
+        }
+        final int shift = (index & 1) << 2;
+        final int i = index >>> 1;
+
+        this.storageUpdating[i] = (byte)((this.storageUpdating[i] & (0xF0 >>> shift)) | (value << shift));
+    }
+
+    public static final class SaveState {
+
+        public final byte[] data;
+        public final int state;
+
+        public SaveState(final byte[] data, final int state) {
+            this.data = data;
+            this.state = state;
+        }
+    }
+}
diff --git a/src/main/java/ca/spottedleaf/starlight/common/light/SkyStarLightEngine.java b/src/main/java/ca/spottedleaf/starlight/common/light/SkyStarLightEngine.java
new file mode 100644
index 0000000000000000000000000000000000000000..5f771962afb44175d446f138c8e7453230f48c6c
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/starlight/common/light/SkyStarLightEngine.java
@@ -0,0 +1,709 @@
+package ca.spottedleaf.starlight.common.light;
+
+import ca.spottedleaf.starlight.common.util.WorldUtil;
+import it.unimi.dsi.fastutil.shorts.ShortCollection;
+import it.unimi.dsi.fastutil.shorts.ShortIterator;
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.BlockGetter;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkStatus;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.world.level.chunk.LightChunkGetter;
+import net.minecraft.world.phys.shapes.Shapes;
+import net.minecraft.world.phys.shapes.VoxelShape;
+import java.util.Arrays;
+import java.util.Set;
+
+public final class SkyStarLightEngine extends StarLightEngine {
+
+    /*
+      Specification for managing the initialisation and de-initialisation of skylight nibble arrays:
+
+      Skylight nibble initialisation requires that non-empty chunk sections have 1 radius nibbles non-null.
+
+      This presents some problems, as vanilla is only guaranteed to have 0 radius neighbours loaded when editing blocks.
+      However starlight fixes this so that it has 1 radius loaded. Still, we don't actually have guarantees
+      that we have the necessary chunks loaded to de-initialise neighbour sections (but we do have enough to de-initialise
+      our own) - we need a radius of 2 to de-initialise neighbour nibbles.
+      How do we solve this?
+
+      Each chunk will store the last known "emptiness" of sections for each of their 1 radius neighbour chunk sections.
+      If the chunk does not have full data, then its nibbles are NOT de-initialised. This is because obviously the
+      chunk did not go through the light stage yet - or its neighbours are not lit. In either case, once the last
+      known "emptiness" of neighbouring sections is filled with data, the chunk will run a full check of the data
+      to see if any of its nibbles need to be de-initialised.
+
+      The emptiness map allows us to de-initialise neighbour nibbles if the neighbour has it filled with data,
+      and if it doesn't have data then we know it will correctly de-initialise once it fills up.
+
+      Unlike vanilla, we store whether nibbles are uninitialised on disk - so we don't need any dumb hacking
+      around those.
+     */
+
+    protected final int[] heightMapBlockChange = new int[16 * 16];
+    {
+        Arrays.fill(this.heightMapBlockChange, Integer.MIN_VALUE); // clear heightmap
+    }
+
+    protected final boolean[] nullPropagationCheckCache;
+
+    public SkyStarLightEngine(final Level world) {
+        super(true, world);
+        this.nullPropagationCheckCache = new boolean[WorldUtil.getTotalLightSections(world)];
+    }
+
+    @Override
+    protected void initNibble(final int chunkX, final int chunkY, final int chunkZ, final boolean extrude, final boolean initRemovedNibbles) {
+        if (chunkY < this.minLightSection || chunkY > this.maxLightSection || this.getChunkInCache(chunkX, chunkZ) == null) {
+            return;
+        }
+        SWMRNibbleArray nibble = this.getNibbleFromCache(chunkX, chunkY, chunkZ);
+        if (nibble == null) {
+            if (!initRemovedNibbles) {
+                throw new IllegalStateException();
+            } else {
+                this.setNibbleInCache(chunkX, chunkY, chunkZ, nibble = new SWMRNibbleArray(null, true));
+            }
+        }
+        this.initNibble(nibble, chunkX, chunkY, chunkZ, extrude);
+    }
+
+    @Override
+    protected void setNibbleNull(final int chunkX, final int chunkY, final int chunkZ) {
+        final SWMRNibbleArray nibble = this.getNibbleFromCache(chunkX, chunkY, chunkZ);
+        if (nibble != null) {
+            nibble.setNull();
+        }
+    }
+
+    protected final void initNibble(final SWMRNibbleArray currNibble, final int chunkX, final int chunkY, final int chunkZ, final boolean extrude) {
+        if (!currNibble.isNullNibbleUpdating()) {
+            // already initialised
+            return;
+        }
+
+        final boolean[] emptinessMap = this.getEmptinessMap(chunkX, chunkZ);
+
+        // are we above this chunk's lowest empty section?
+        int lowestY = this.minLightSection - 1;
+        for (int currY = this.maxSection; currY >= this.minSection; --currY) {
+            if (emptinessMap == null) {
+                // cannot delay nibble init for lit chunks, as we need to init to propagate into them.
+                final LevelChunkSection current = this.getChunkSection(chunkX, currY, chunkZ);
+                if (current == null || current.hasOnlyAir()) {
+                    continue;
+                }
+            } else {
+                if (emptinessMap[currY - this.minSection]) {
+                    continue;
+                }
+            }
+
+            // should always be full lit here
+            lowestY = currY;
+            break;
+        }
+
+        if (chunkY > lowestY) {
+            // we need to set this one to full
+            final SWMRNibbleArray nibble = this.getNibbleFromCache(chunkX, chunkY, chunkZ);
+            nibble.setNonNull();
+            nibble.setFull();
+            return;
+        }
+
+        if (extrude) {
+            // this nibble is going to depend solely on the skylight data above it
+            // find first non-null data above (there does exist one, as we just found it above)
+            for (int currY = chunkY + 1; currY <= this.maxLightSection; ++currY) {
+                final SWMRNibbleArray nibble = this.getNibbleFromCache(chunkX, currY, chunkZ);
+                if (nibble != null && !nibble.isNullNibbleUpdating()) {
+                    currNibble.setNonNull();
+                    currNibble.extrudeLower(nibble);
+                    break;
+                }
+            }
+        } else {
+            currNibble.setNonNull();
+        }
+    }
+
+    protected final void rewriteNibbleCacheForSkylight(final ChunkAccess chunk) {
+        for (int index = 0, max = this.nibbleCache.length; index < max; ++index) {
+            final SWMRNibbleArray nibble = this.nibbleCache[index];
+            if (nibble != null && nibble.isNullNibbleUpdating()) {
+                // stop propagation in these areas
+                this.nibbleCache[index] = null;
+                nibble.updateVisible();
+            }
+        }
+    }
+
+    // rets whether neighbours were init'd
+
+    protected final boolean checkNullSection(final int chunkX, final int chunkY, final int chunkZ,
+                                             final boolean extrudeInitialised) {
+        // null chunk sections may have nibble neighbours in the horizontal 1 radius that are
+        // non-null. Propagation to these neighbours is necessary.
+        // What makes this easy is we know none of these neighbours are non-empty (otherwise
+        // this nibble would be initialised). So, we don't have to initialise
+        // the neighbours in the full 1 radius, because there's no worry that any "paths"
+        // to the neighbours on this horizontal plane are blocked.
+        if (chunkY < this.minLightSection || chunkY > this.maxLightSection || this.nullPropagationCheckCache[chunkY - this.minLightSection]) {
+            return false;
+        }
+        this.nullPropagationCheckCache[chunkY - this.minLightSection] = true;
+
+        // check horizontal neighbours
+        boolean needInitNeighbours = false;
+        neighbour_search:
+        for (int dz = -1; dz <= 1; ++dz) {
+            for (int dx = -1; dx <= 1; ++dx) {
+                final SWMRNibbleArray nibble = this.getNibbleFromCache(dx + chunkX, chunkY, dz + chunkZ);
+                if (nibble != null && !nibble.isNullNibbleUpdating()) {
+                    needInitNeighbours = true;
+                    break neighbour_search;
+                }
+            }
+        }
+
+        if (needInitNeighbours) {
+            for (int dz = -1; dz <= 1; ++dz) {
+                for (int dx = -1; dx <= 1; ++dx) {
+                    this.initNibble(dx + chunkX, chunkY, dz + chunkZ, (dx | dz) == 0 ? extrudeInitialised : true, true);
+                }
+            }
+        }
+
+        return needInitNeighbours;
+    }
+
+    protected final int getLightLevelExtruded(final int worldX, final int worldY, final int worldZ) {
+        final int chunkX = worldX >> 4;
+        int chunkY = worldY >> 4;
+        final int chunkZ = worldZ >> 4;
+
+        SWMRNibbleArray nibble = this.getNibbleFromCache(chunkX, chunkY, chunkZ);
+        if (nibble != null) {
+            return nibble.getUpdating(worldX, worldY, worldZ);
+        }
+
+        for (;;) {
+            if (++chunkY > this.maxLightSection) {
+                return 15;
+            }
+
+            nibble = this.getNibbleFromCache(chunkX, chunkY, chunkZ);
+
+            if (nibble != null) {
+                return nibble.getUpdating(worldX, 0, worldZ);
+            }
+        }
+    }
+
+    @Override
+    protected boolean[] getEmptinessMap(final ChunkAccess chunk) {
+        return chunk.getSkyEmptinessMap();
+    }
+
+    @Override
+    protected void setEmptinessMap(final ChunkAccess chunk, final boolean[] to) {
+        chunk.setSkyEmptinessMap(to);
+    }
+
+    @Override
+    protected SWMRNibbleArray[] getNibblesOnChunk(final ChunkAccess chunk) {
+        return chunk.getSkyNibbles();
+    }
+
+    @Override
+    protected void setNibbles(final ChunkAccess chunk, final SWMRNibbleArray[] to) {
+        chunk.setSkyNibbles(to);
+    }
+
+    @Override
+    protected boolean canUseChunk(final ChunkAccess chunk) {
+        // can only use chunks for sky stuff if their sections have been init'd
+        return chunk.getStatus().isOrAfter(ChunkStatus.LIGHT) && (this.isClientSide || chunk.isLightCorrect());
+    }
+
+    @Override
+    protected void checkChunkEdges(final LightChunkGetter lightAccess, final ChunkAccess chunk, final int fromSection,
+                                   final int toSection) {
+        Arrays.fill(this.nullPropagationCheckCache, false);
+        this.rewriteNibbleCacheForSkylight(chunk);
+        final int chunkX = chunk.getPos().x;
+        final int chunkZ = chunk.getPos().z;
+        for (int y = toSection; y >= fromSection; --y) {
+            this.checkNullSection(chunkX, y, chunkZ, true);
+        }
+
+        super.checkChunkEdges(lightAccess, chunk, fromSection, toSection);
+    }
+
+    @Override
+    protected void checkChunkEdges(final LightChunkGetter lightAccess, final ChunkAccess chunk, final ShortCollection sections) {
+        Arrays.fill(this.nullPropagationCheckCache, false);
+        this.rewriteNibbleCacheForSkylight(chunk);
+        final int chunkX = chunk.getPos().x;
+        final int chunkZ = chunk.getPos().z;
+        for (final ShortIterator iterator = sections.iterator(); iterator.hasNext();) {
+            final int y = (int)iterator.nextShort();
+            this.checkNullSection(chunkX, y, chunkZ, true);
+        }
+
+        super.checkChunkEdges(lightAccess, chunk, sections);
+    }
+
+    @Override
+    protected void checkBlock(final LightChunkGetter lightAccess, final int worldX, final int worldY, final int worldZ) {
+        // blocks can change opacity
+        // blocks can change direction of propagation
+
+        // same logic applies from BlockStarLightEngine#checkBlock
+
+        final int encodeOffset = this.coordinateOffset;
+
+        final int currentLevel = this.getLightLevel(worldX, worldY, worldZ);
+
+        if (currentLevel == 15) {
+            // must re-propagate clobbered source
+            this.appendToIncreaseQueue(
+                    ((worldX + (worldZ << 6) + (worldY << (6 + 6)) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                            | (currentLevel & 0xFL) << (6 + 6 + 16)
+                            | (((long)ALL_DIRECTIONS_BITSET) << (6 + 6 + 16 + 4))
+                            | FLAG_HAS_SIDED_TRANSPARENT_BLOCKS // don't know if the block is conditionally transparent
+            );
+        } else {
+            this.setLightLevel(worldX, worldY, worldZ, 0);
+        }
+
+        this.appendToDecreaseQueue(
+                ((worldX + (worldZ << 6) + (worldY << (6 + 6)) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                        | (currentLevel & 0xFL) << (6 + 6 + 16)
+                        | (((long)ALL_DIRECTIONS_BITSET) << (6 + 6 + 16 + 4))
+        );
+    }
+
+    protected final BlockPos.MutableBlockPos recalcCenterPos = new BlockPos.MutableBlockPos();
+    protected final BlockPos.MutableBlockPos recalcNeighbourPos = new BlockPos.MutableBlockPos();
+
+    @Override
+    protected int calculateLightValue(final LightChunkGetter lightAccess, final int worldX, final int worldY, final int worldZ,
+                                      final int expect) {
+        if (expect == 15) {
+            return expect;
+        }
+
+        final int sectionOffset = this.chunkSectionIndexOffset;
+        final BlockState centerState = this.getBlockState(worldX, worldY, worldZ);
+        int opacity = centerState.getOpacityIfCached();
+
+        final BlockState conditionallyOpaqueState;
+        if (opacity < 0) {
+            this.recalcCenterPos.set(worldX, worldY, worldZ);
+            opacity = Math.max(1, centerState.getLightBlock(lightAccess.getLevel(), this.recalcCenterPos));
+            if (centerState.isConditionallyFullOpaque()) {
+                conditionallyOpaqueState = centerState;
+            } else {
+                conditionallyOpaqueState = null;
+            }
+        } else {
+            conditionallyOpaqueState = null;
+            opacity = Math.max(1, opacity);
+        }
+
+        int level = 0;
+
+        for (final AxisDirection direction : AXIS_DIRECTIONS) {
+            final int offX = worldX + direction.x;
+            final int offY = worldY + direction.y;
+            final int offZ = worldZ + direction.z;
+
+            final int sectionIndex = (offX >> 4) + 5 * (offZ >> 4) + (5 * 5) * (offY >> 4) + sectionOffset;
+
+            final int neighbourLevel = this.getLightLevel(sectionIndex, (offX & 15) | ((offZ & 15) << 4) | ((offY & 15) << 8));
+
+            if ((neighbourLevel - 1) <= level) {
+                // don't need to test transparency, we know it wont affect the result.
+                continue;
+            }
+
+            final BlockState neighbourState = this.getBlockState(offX, offY, offZ);
+
+            if (neighbourState.isConditionallyFullOpaque()) {
+                // here the block can be conditionally opaque (i.e light cannot propagate from it), so we need to test that
+                // we don't read the blockstate because most of the time this is false, so using the faster
+                // known transparency lookup results in a net win
+                this.recalcNeighbourPos.set(offX, offY, offZ);
+                final VoxelShape neighbourFace = neighbourState.getFaceOcclusionShape(lightAccess.getLevel(), this.recalcNeighbourPos, direction.opposite.nms);
+                final VoxelShape thisFace = conditionallyOpaqueState == null ? Shapes.empty() : conditionallyOpaqueState.getFaceOcclusionShape(lightAccess.getLevel(), this.recalcCenterPos, direction.nms);
+                if (Shapes.faceShapeOccludes(thisFace, neighbourFace)) {
+                    // not allowed to propagate
+                    continue;
+                }
+            }
+
+            final int calculated = neighbourLevel - opacity;
+            level = Math.max(calculated, level);
+            if (level > expect) {
+                return level;
+            }
+        }
+
+        return level;
+    }
+
+    @Override
+    protected void propagateBlockChanges(final LightChunkGetter lightAccess, final ChunkAccess atChunk, final Set<BlockPos> positions) {
+        this.rewriteNibbleCacheForSkylight(atChunk);
+        Arrays.fill(this.nullPropagationCheckCache, false);
+
+        final BlockGetter world = lightAccess.getLevel();
+        final int chunkX = atChunk.getPos().x;
+        final int chunkZ = atChunk.getPos().z;
+        final int heightMapOffset = chunkX * -16 + (chunkZ * (-16 * 16));
+
+        // setup heightmap for changes
+        for (final BlockPos pos : positions) {
+            final int index = pos.getX() + (pos.getZ() << 4) + heightMapOffset;
+            final int curr = this.heightMapBlockChange[index];
+            if (pos.getY() > curr) {
+                this.heightMapBlockChange[index] = pos.getY();
+            }
+        }
+
+        // note: light sets are delayed while processing skylight source changes due to how
+        // nibbles are initialised, as we want to avoid clobbering nibble values so what when
+        // below nibbles are initialised they aren't reading from partially modified nibbles
+
+        // now we can recalculate the sources for the changed columns
+        for (int index = 0; index < (16 * 16); ++index) {
+            final int maxY = this.heightMapBlockChange[index];
+            if (maxY == Integer.MIN_VALUE) {
+                // not changed
+                continue;
+            }
+            this.heightMapBlockChange[index] = Integer.MIN_VALUE; // restore default for next caller
+
+            final int columnX = (index & 15) | (chunkX << 4);
+            final int columnZ = (index >>> 4) | (chunkZ << 4);
+
+            // try and propagate from the above y
+            // delay light set until after processing all sources to setup
+            final int maxPropagationY = this.tryPropagateSkylight(world, columnX, maxY, columnZ, true, true);
+
+            // maxPropagationY is now the highest block that could not be propagated to
+
+            // remove all sources below that are 15
+            final long propagateDirection = AxisDirection.POSITIVE_Y.everythingButThisDirection;
+            final int encodeOffset = this.coordinateOffset;
+
+            if (this.getLightLevelExtruded(columnX, maxPropagationY, columnZ) == 15) {
+                // ensure section is checked
+                this.checkNullSection(columnX >> 4, maxPropagationY >> 4, columnZ >> 4, true);
+
+                for (int currY = maxPropagationY; currY >= (this.minLightSection << 4); --currY) {
+                    if ((currY & 15) == 15) {
+                        // ensure section is checked
+                        this.checkNullSection(columnX >> 4, (currY >> 4), columnZ >> 4, true);
+                    }
+
+                    // ensure section below is always checked
+                    final SWMRNibbleArray nibble = this.getNibbleFromCache(columnX >> 4, currY >> 4, columnZ >> 4);
+                    if (nibble == null) {
+                        // advance currY to the the top of the section below
+                        currY = (currY) & (~15);
+                        // note: this value ^ is actually 1 above the top, but the loop decrements by 1 so we actually
+                        // end up there
+                        continue;
+                    }
+
+                    if (nibble.getUpdating(columnX, currY, columnZ) != 15) {
+                        break;
+                    }
+
+                    // delay light set until after processing all sources to setup
+                    this.appendToDecreaseQueue(
+                            ((columnX + (columnZ << 6) + (currY << (6 + 6)) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                    | (15L << (6 + 6 + 16))
+                                    | (propagateDirection << (6 + 6 + 16 + 4))
+                                    // do not set transparent blocks for the same reason we don't in the checkBlock method
+                    );
+                }
+            }
+        }
+
+        // delayed light sets are processed here, and must be processed before checkBlock as checkBlock reads
+        // immediate light value
+        this.processDelayedIncreases();
+        this.processDelayedDecreases();
+
+        for (final BlockPos pos : positions) {
+            this.checkBlock(lightAccess, pos.getX(), pos.getY(), pos.getZ());
+        }
+
+        this.performLightDecrease(lightAccess);
+    }
+
+    protected final int[] heightMapGen = new int[32 * 32];
+
+    @Override
+    protected void lightChunk(final LightChunkGetter lightAccess, final ChunkAccess chunk, final boolean needsEdgeChecks) {
+        this.rewriteNibbleCacheForSkylight(chunk);
+        Arrays.fill(this.nullPropagationCheckCache, false);
+
+        final BlockGetter world = lightAccess.getLevel();
+        final ChunkPos chunkPos = chunk.getPos();
+        final int chunkX = chunkPos.x;
+        final int chunkZ = chunkPos.z;
+
+        final LevelChunkSection[] sections = chunk.getSections();
+
+        int highestNonEmptySection = this.maxSection;
+        while (highestNonEmptySection == (this.minSection - 1) ||
+                sections[highestNonEmptySection - this.minSection] == null || sections[highestNonEmptySection - this.minSection].hasOnlyAir()) {
+            this.checkNullSection(chunkX, highestNonEmptySection, chunkZ, false);
+            // try propagate FULL to neighbours
+
+            // check neighbours to see if we need to propagate into them
+            for (final AxisDirection direction : ONLY_HORIZONTAL_DIRECTIONS) {
+                final int neighbourX = chunkX + direction.x;
+                final int neighbourZ = chunkZ + direction.z;
+                final SWMRNibbleArray neighbourNibble = this.getNibbleFromCache(neighbourX, highestNonEmptySection, neighbourZ);
+                if (neighbourNibble == null) {
+                    // unloaded neighbour
+                    // most of the time we fall here
+                    continue;
+                }
+
+                // it looks like we need to propagate into the neighbour
+
+                final int incX;
+                final int incZ;
+                final int startX;
+                final int startZ;
+
+                if (direction.x != 0) {
+                    // x direction
+                    incX = 0;
+                    incZ = 1;
+
+                    if (direction.x < 0) {
+                        // negative
+                        startX = chunkX << 4;
+                    } else {
+                        startX = chunkX << 4 | 15;
+                    }
+                    startZ = chunkZ << 4;
+                } else {
+                    // z direction
+                    incX = 1;
+                    incZ = 0;
+
+                    if (direction.z < 0) {
+                        // negative
+                        startZ = chunkZ << 4;
+                    } else {
+                        startZ = chunkZ << 4 | 15;
+                    }
+                    startX = chunkX << 4;
+                }
+
+                final int encodeOffset = this.coordinateOffset;
+                final long propagateDirection = 1L << direction.ordinal(); // we only want to check in this direction
+
+                for (int currY = highestNonEmptySection << 4, maxY = currY | 15; currY <= maxY; ++currY) {
+                    for (int i = 0, currX = startX, currZ = startZ; i < 16; ++i, currX += incX, currZ += incZ) {
+                        this.appendToIncreaseQueue(
+                                ((currX + (currZ << 6) + (currY << (6 + 6)) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                        | (15L << (6 + 6 + 16)) // we know we're at full lit here
+                                        | (propagateDirection << (6 + 6 + 16 + 4))
+                                        // no transparent flag, we know for a fact there are no blocks here that could be directionally transparent (as the section is EMPTY)
+                        );
+                    }
+                }
+            }
+
+            if (highestNonEmptySection-- == (this.minSection - 1)) {
+                break;
+            }
+        }
+
+        if (highestNonEmptySection >= this.minSection) {
+            // fill out our other sources
+            final int minX = chunkPos.x << 4;
+            final int maxX = chunkPos.x << 4 | 15;
+            final int minZ = chunkPos.z << 4;
+            final int maxZ = chunkPos.z << 4 | 15;
+            final int startY = highestNonEmptySection << 4 | 15;
+            for (int currZ = minZ; currZ <= maxZ; ++currZ) {
+                for (int currX = minX; currX <= maxX; ++currX) {
+                    this.tryPropagateSkylight(world, currX, startY + 1, currZ, false, false);
+                }
+            }
+        } // else: apparently the chunk is empty
+
+        if (needsEdgeChecks) {
+            // not required to propagate here, but this will reduce the hit of the edge checks
+            this.performLightIncrease(lightAccess);
+
+            for (int y = highestNonEmptySection; y >= this.minLightSection; --y) {
+                this.checkNullSection(chunkX, y, chunkZ, false);
+            }
+            // no need to rewrite the nibble cache again
+            super.checkChunkEdges(lightAccess, chunk, this.minLightSection, highestNonEmptySection);
+        } else {
+            for (int y = highestNonEmptySection; y >= this.minLightSection; --y) {
+                this.checkNullSection(chunkX, y, chunkZ, false);
+            }
+            this.propagateNeighbourLevels(lightAccess, chunk, this.minLightSection, highestNonEmptySection);
+
+            this.performLightIncrease(lightAccess);
+        }
+    }
+
+    protected final void processDelayedIncreases() {
+        // copied from performLightIncrease
+        final long[] queue = this.increaseQueue;
+        final int decodeOffsetX = -this.encodeOffsetX;
+        final int decodeOffsetY = -this.encodeOffsetY;
+        final int decodeOffsetZ = -this.encodeOffsetZ;
+
+        for (int i = 0, len = this.increaseQueueInitialLength; i < len; ++i) {
+            final long queueValue = queue[i];
+
+            final int posX = ((int)queueValue & 63) + decodeOffsetX;
+            final int posZ = (((int)queueValue >>> 6) & 63) + decodeOffsetZ;
+            final int posY = (((int)queueValue >>> 12) & ((1 << 16) - 1)) + decodeOffsetY;
+            final int propagatedLightLevel = (int)((queueValue >>> (6 + 6 + 16)) & 0xF);
+
+            this.setLightLevel(posX, posY, posZ, propagatedLightLevel);
+        }
+    }
+
+    protected final void processDelayedDecreases() {
+        // copied from performLightDecrease
+        final long[] queue = this.decreaseQueue;
+        final int decodeOffsetX = -this.encodeOffsetX;
+        final int decodeOffsetY = -this.encodeOffsetY;
+        final int decodeOffsetZ = -this.encodeOffsetZ;
+
+        for (int i = 0, len = this.decreaseQueueInitialLength; i < len; ++i) {
+            final long queueValue = queue[i];
+
+            final int posX = ((int)queueValue & 63) + decodeOffsetX;
+            final int posZ = (((int)queueValue >>> 6) & 63) + decodeOffsetZ;
+            final int posY = (((int)queueValue >>> 12) & ((1 << 16) - 1)) + decodeOffsetY;
+
+            this.setLightLevel(posX, posY, posZ, 0);
+        }
+    }
+
+    // delaying the light set is useful for block changes since they need to worry about initialising nibblearrays
+    // while also queueing light at the same time (initialising nibblearrays might depend on nibbles above, so
+    // clobbering the light values will result in broken propagation)
+    protected final int tryPropagateSkylight(final BlockGetter world, final int worldX, int startY, final int worldZ,
+                                             final boolean extrudeInitialised, final boolean delayLightSet) {
+        final BlockPos.MutableBlockPos mutablePos = this.mutablePos3;
+        final int encodeOffset = this.coordinateOffset;
+        final long propagateDirection = AxisDirection.POSITIVE_Y.everythingButThisDirection; // just don't check upwards.
+
+        if (this.getLightLevelExtruded(worldX, startY + 1, worldZ) != 15) {
+            return startY;
+        }
+
+        // ensure this section is always checked
+        this.checkNullSection(worldX >> 4, startY >> 4, worldZ >> 4, extrudeInitialised);
+
+        BlockState above = this.getBlockState(worldX, startY + 1, worldZ);
+
+        for (;startY >= (this.minLightSection << 4); --startY) {
+            if ((startY & 15) == 15) {
+                // ensure this section is always checked
+                this.checkNullSection(worldX >> 4, startY >> 4, worldZ >> 4, extrudeInitialised);
+            }
+            final BlockState current = this.getBlockState(worldX, startY, worldZ);
+
+            final VoxelShape fromShape;
+            if (above.isConditionallyFullOpaque()) {
+                this.mutablePos2.set(worldX, startY + 1, worldZ);
+                fromShape = above.getFaceOcclusionShape(world, this.mutablePos2, AxisDirection.NEGATIVE_Y.nms);
+                if (Shapes.faceShapeOccludes(Shapes.empty(), fromShape)) {
+                    // above wont let us propagate
+                    break;
+                }
+            } else {
+                fromShape = Shapes.empty();
+            }
+
+            final int opacityIfCached = current.getOpacityIfCached();
+            // does light propagate from the top down?
+            if (opacityIfCached != -1) {
+                if (opacityIfCached != 0) {
+                    // we cannot propagate 15 through this
+                    break;
+                }
+                // most of the time it falls here.
+                // add to propagate
+                // light set delayed until we determine if this nibble section is null
+                this.appendToIncreaseQueue(
+                        ((worldX + (worldZ << 6) + (startY << (6 + 6)) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                | (15L << (6 + 6 + 16)) // we know we're at full lit here
+                                | (propagateDirection << (6 + 6 + 16 + 4))
+                );
+            } else {
+                mutablePos.set(worldX, startY, worldZ);
+                long flags = 0L;
+                if (current.isConditionallyFullOpaque()) {
+                    final VoxelShape cullingFace = current.getFaceOcclusionShape(world, mutablePos, AxisDirection.POSITIVE_Y.nms);
+
+                    if (Shapes.faceShapeOccludes(fromShape, cullingFace)) {
+                        // can't propagate here, we're done on this column.
+                        break;
+                    }
+                    flags |= FLAG_HAS_SIDED_TRANSPARENT_BLOCKS;
+                }
+
+                final int opacity = current.getLightBlock(world, mutablePos);
+                if (opacity > 0) {
+                    // let the queued value (if any) handle it from here.
+                    break;
+                }
+
+                // light set delayed until we determine if this nibble section is null
+                this.appendToIncreaseQueue(
+                        ((worldX + (worldZ << 6) + (startY << (6 + 6)) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                | (15L << (6 + 6 + 16)) // we know we're at full lit here
+                                | (propagateDirection << (6 + 6 + 16 + 4))
+                                | flags
+                );
+            }
+
+            above = current;
+
+            if (this.getNibbleFromCache(worldX >> 4, startY >> 4, worldZ >> 4) == null) {
+                // we skip empty sections here, as this is just an easy way of making sure the above block
+                // can propagate through air.
+
+                // nothing can propagate in null sections, remove the queue entry for it
+                --this.increaseQueueInitialLength;
+
+                // advance currY to the the top of the section below
+                startY = (startY) & (~15);
+                // note: this value ^ is actually 1 above the top, but the loop decrements by 1 so we actually
+                // end up there
+
+                // make sure this is marked as AIR
+                above = AIR_BLOCK_STATE;
+            } else if (!delayLightSet) {
+                this.setLightLevel(worldX, startY, worldZ, 15);
+            }
+        }
+
+        return startY;
+    }
+}
diff --git a/src/main/java/ca/spottedleaf/starlight/common/light/StarLightEngine.java b/src/main/java/ca/spottedleaf/starlight/common/light/StarLightEngine.java
new file mode 100644
index 0000000000000000000000000000000000000000..ad1eeebe6de219143492b94da309cb54ae9e0a5b
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/starlight/common/light/StarLightEngine.java
@@ -0,0 +1,1572 @@
+package ca.spottedleaf.starlight.common.light;
+
+import ca.spottedleaf.starlight.common.util.CoordinateUtils;
+import ca.spottedleaf.starlight.common.util.IntegerUtil;
+import ca.spottedleaf.starlight.common.util.WorldUtil;
+import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
+import it.unimi.dsi.fastutil.shorts.ShortCollection;
+import it.unimi.dsi.fastutil.shorts.ShortIterator;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.core.SectionPos;
+import net.minecraft.world.level.BlockGetter;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.LightLayer;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.world.level.chunk.LightChunkGetter;
+import net.minecraft.world.phys.shapes.Shapes;
+import net.minecraft.world.phys.shapes.VoxelShape;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Set;
+import java.util.function.Consumer;
+import java.util.function.IntConsumer;
+
+public abstract class StarLightEngine {
+
+    protected static final BlockState AIR_BLOCK_STATE = Blocks.AIR.defaultBlockState();
+
+    protected static final AxisDirection[] DIRECTIONS = AxisDirection.values();
+    protected static final AxisDirection[] AXIS_DIRECTIONS = DIRECTIONS;
+    protected static final AxisDirection[] ONLY_HORIZONTAL_DIRECTIONS = new AxisDirection[] {
+            AxisDirection.POSITIVE_X, AxisDirection.NEGATIVE_X,
+            AxisDirection.POSITIVE_Z, AxisDirection.NEGATIVE_Z
+    };
+
+    protected static enum AxisDirection {
+
+        // Declaration order is important and relied upon. Do not change without modifying propagation code.
+        POSITIVE_X(1, 0, 0), NEGATIVE_X(-1, 0, 0),
+        POSITIVE_Z(0, 0, 1), NEGATIVE_Z(0, 0, -1),
+        POSITIVE_Y(0, 1, 0), NEGATIVE_Y(0, -1, 0);
+
+        static {
+            POSITIVE_X.opposite = NEGATIVE_X; NEGATIVE_X.opposite = POSITIVE_X;
+            POSITIVE_Z.opposite = NEGATIVE_Z; NEGATIVE_Z.opposite = POSITIVE_Z;
+            POSITIVE_Y.opposite = NEGATIVE_Y; NEGATIVE_Y.opposite = POSITIVE_Y;
+        }
+
+        protected AxisDirection opposite;
+
+        public final int x;
+        public final int y;
+        public final int z;
+        public final Direction nms;
+        public final long everythingButThisDirection;
+        public final long everythingButTheOppositeDirection;
+
+        AxisDirection(final int x, final int y, final int z) {
+            this.x = x;
+            this.y = y;
+            this.z = z;
+            this.nms = Direction.fromDelta(x, y, z);
+            this.everythingButThisDirection = (long)(ALL_DIRECTIONS_BITSET ^ (1 << this.ordinal()));
+            // positive is always even, negative is always odd. Flip the 1 bit to get the negative direction.
+            this.everythingButTheOppositeDirection = (long)(ALL_DIRECTIONS_BITSET ^ (1 << (this.ordinal() ^ 1)));
+        }
+
+        public AxisDirection getOpposite() {
+            return this.opposite;
+        }
+    }
+
+    // I'd like to thank https://www.seedofandromeda.com/blogs/29-fast-flood-fill-lighting-in-a-blocky-voxel-game-pt-1
+    // for explaining how light propagates via breadth-first search
+
+    // While the above is a good start to understanding the general idea of what the general principles are, it's not
+    // exactly how the vanilla light engine should behave for minecraft.
+
+    // similar to the above, except the chunk section indices vary from [-1, 1], or [0, 2]
+    // for the y chunk section it's from [minLightSection, maxLightSection] or [0, maxLightSection - minLightSection]
+    // index = x + (z * 5) + (y * 25)
+    // null index indicates the chunk section doesn't exist (empty or out of bounds)
+    protected final LevelChunkSection[] sectionCache;
+
+    // the exact same as above, except for storing fast access to SWMRNibbleArray
+    // for the y chunk section it's from [minLightSection, maxLightSection] or [0, maxLightSection - minLightSection]
+    // index = x + (z * 5) + (y * 25)
+    protected final SWMRNibbleArray[] nibbleCache;
+
+    // the exact same as above, except for storing fast access to nibbles to call change callbacks for
+    // for the y chunk section it's from [minLightSection, maxLightSection] or [0, maxLightSection - minLightSection]
+    // index = x + (z * 5) + (y * 25)
+    protected final boolean[] notifyUpdateCache;
+
+    // always initialsed during start of lighting.
+    // index = x + (z * 5)
+    protected final ChunkAccess[] chunkCache = new ChunkAccess[5 * 5];
+
+    // index = x + (z * 5)
+    protected final boolean[][] emptinessMapCache = new boolean[5 * 5][];
+
+    protected final BlockPos.MutableBlockPos mutablePos1 = new BlockPos.MutableBlockPos();
+    protected final BlockPos.MutableBlockPos mutablePos2 = new BlockPos.MutableBlockPos();
+    protected final BlockPos.MutableBlockPos mutablePos3 = new BlockPos.MutableBlockPos();
+
+    protected int encodeOffsetX;
+    protected int encodeOffsetY;
+    protected int encodeOffsetZ;
+
+    protected int coordinateOffset;
+
+    protected int chunkOffsetX;
+    protected int chunkOffsetY;
+    protected int chunkOffsetZ;
+
+    protected int chunkIndexOffset;
+    protected int chunkSectionIndexOffset;
+
+    protected final boolean skylightPropagator;
+    protected final int emittedLightMask;
+    protected final boolean isClientSide;
+
+    protected final Level world;
+    protected final int minLightSection;
+    protected final int maxLightSection;
+    protected final int minSection;
+    protected final int maxSection;
+
+    protected StarLightEngine(final boolean skylightPropagator, final Level world) {
+        this.skylightPropagator = skylightPropagator;
+        this.emittedLightMask = skylightPropagator ? 0 : 0xF;
+        this.isClientSide = world.isClientSide;
+        this.world = world;
+        this.minLightSection = WorldUtil.getMinLightSection(world);
+        this.maxLightSection = WorldUtil.getMaxLightSection(world);
+        this.minSection = WorldUtil.getMinSection(world);
+        this.maxSection = WorldUtil.getMaxSection(world);
+
+        this.sectionCache = new LevelChunkSection[5 * 5 * ((this.maxLightSection - this.minLightSection + 1) + 2)]; // add two extra sections for buffer
+        this.nibbleCache = new SWMRNibbleArray[5 * 5 * ((this.maxLightSection - this.minLightSection + 1) + 2)]; // add two extra sections for buffer
+        this.notifyUpdateCache = new boolean[5 * 5 * ((this.maxLightSection - this.minLightSection + 1) + 2)]; // add two extra sections for buffer
+    }
+
+    protected final void setupEncodeOffset(final int centerX, final int centerY, final int centerZ) {
+        // 31 = center + encodeOffset
+        this.encodeOffsetX = 31 - centerX;
+        this.encodeOffsetY = (-(this.minLightSection - 1) << 4); // we want 0 to be the smallest encoded value
+        this.encodeOffsetZ = 31 - centerZ;
+
+        // coordinateIndex = x | (z << 6) | (y << 12)
+        this.coordinateOffset = this.encodeOffsetX + (this.encodeOffsetZ << 6) + (this.encodeOffsetY << 12);
+
+        // 2 = (centerX >> 4) + chunkOffset
+        this.chunkOffsetX = 2 - (centerX >> 4);
+        this.chunkOffsetY = -(this.minLightSection - 1); // lowest should be 0
+        this.chunkOffsetZ = 2 - (centerZ >> 4);
+
+        // chunk index = x + (5 * z)
+        this.chunkIndexOffset = this.chunkOffsetX + (5 * this.chunkOffsetZ);
+
+        // chunk section index = x + (5 * z) + ((5*5) * y)
+        this.chunkSectionIndexOffset = this.chunkIndexOffset + ((5 * 5) * this.chunkOffsetY);
+    }
+
+    protected final void setupCaches(final LightChunkGetter chunkProvider, final int centerX, final int centerY, final int centerZ,
+                                     final boolean relaxed, final boolean tryToLoadChunksFor2Radius) {
+        final int centerChunkX = centerX >> 4;
+        final int centerChunkY = centerY >> 4;
+        final int centerChunkZ = centerZ >> 4;
+
+        this.setupEncodeOffset(centerChunkX * 16 + 7, centerChunkY * 16 + 7, centerChunkZ * 16 + 7);
+
+        final int radius = tryToLoadChunksFor2Radius ? 2 : 1;
+
+        for (int dz = -radius; dz <= radius; ++dz) {
+            for (int dx = -radius; dx <= radius; ++dx) {
+                final int cx = centerChunkX + dx;
+                final int cz = centerChunkZ + dz;
+                final boolean isTwoRadius = Math.max(IntegerUtil.branchlessAbs(dx), IntegerUtil.branchlessAbs(dz)) == 2;
+                final ChunkAccess chunk = (ChunkAccess)chunkProvider.getChunkForLighting(cx, cz);
+
+                if (chunk == null) {
+                    if (relaxed | isTwoRadius) {
+                        continue;
+                    }
+                    throw new IllegalArgumentException("Trying to propagate light update before 1 radius neighbours ready");
+                }
+
+                if (!this.canUseChunk(chunk)) {
+                    continue;
+                }
+
+                this.setChunkInCache(cx, cz, chunk);
+                this.setEmptinessMapCache(cx, cz, this.getEmptinessMap(chunk));
+                if (!isTwoRadius) {
+                    this.setBlocksForChunkInCache(cx, cz, chunk.getSections());
+                    this.setNibblesForChunkInCache(cx, cz, this.getNibblesOnChunk(chunk));
+                }
+            }
+        }
+    }
+
+    protected final ChunkAccess getChunkInCache(final int chunkX, final int chunkZ) {
+        return this.chunkCache[chunkX + 5*chunkZ + this.chunkIndexOffset];
+    }
+
+    protected final void setChunkInCache(final int chunkX, final int chunkZ, final ChunkAccess chunk) {
+        this.chunkCache[chunkX + 5*chunkZ + this.chunkIndexOffset] = chunk;
+    }
+
+    protected final LevelChunkSection getChunkSection(final int chunkX, final int chunkY, final int chunkZ) {
+        return this.sectionCache[chunkX + 5*chunkZ + (5 * 5) * chunkY + this.chunkSectionIndexOffset];
+    }
+
+    protected final void setChunkSectionInCache(final int chunkX, final int chunkY, final int chunkZ, final LevelChunkSection section) {
+        this.sectionCache[chunkX + 5*chunkZ + 5*5*chunkY + this.chunkSectionIndexOffset] = section;
+    }
+
+    protected final void setBlocksForChunkInCache(final int chunkX, final int chunkZ, final LevelChunkSection[] sections) {
+        for (int cy = this.minLightSection; cy <= this.maxLightSection; ++cy) {
+            this.setChunkSectionInCache(chunkX, cy, chunkZ,
+                    sections == null ? null : (cy >= this.minSection && cy <= this.maxSection ? sections[cy - this.minSection] : null));
+        }
+    }
+
+    protected final SWMRNibbleArray getNibbleFromCache(final int chunkX, final int chunkY, final int chunkZ) {
+        return this.nibbleCache[chunkX + 5*chunkZ + (5 * 5) * chunkY + this.chunkSectionIndexOffset];
+    }
+
+    protected final SWMRNibbleArray[] getNibblesForChunkFromCache(final int chunkX, final int chunkZ) {
+        final SWMRNibbleArray[] ret = new SWMRNibbleArray[this.maxLightSection - this.minLightSection + 1];
+
+        for (int cy = this.minLightSection; cy <= this.maxLightSection; ++cy) {
+            ret[cy - this.minLightSection] = this.nibbleCache[chunkX + 5*chunkZ + (cy * (5 * 5)) + this.chunkSectionIndexOffset];
+        }
+
+        return ret;
+    }
+
+    protected final void setNibbleInCache(final int chunkX, final int chunkY, final int chunkZ, final SWMRNibbleArray nibble) {
+        this.nibbleCache[chunkX + 5*chunkZ + (5 * 5) * chunkY + this.chunkSectionIndexOffset] = nibble;
+    }
+
+    protected final void setNibblesForChunkInCache(final int chunkX, final int chunkZ, final SWMRNibbleArray[] nibbles) {
+        for (int cy = this.minLightSection; cy <= this.maxLightSection; ++cy) {
+            this.setNibbleInCache(chunkX, cy, chunkZ, nibbles == null ? null : nibbles[cy - this.minLightSection]);
+        }
+    }
+
+    protected final void updateVisible(final LightChunkGetter lightAccess) {
+        for (int index = 0, max = this.nibbleCache.length; index < max; ++index) {
+            final SWMRNibbleArray nibble = this.nibbleCache[index];
+            if (!this.notifyUpdateCache[index] && (nibble == null || !nibble.isDirty())) {
+                continue;
+            }
+
+            final int chunkX = (index % 5) - this.chunkOffsetX;
+            final int chunkZ = ((index / 5) % 5) - this.chunkOffsetZ;
+            final int ySections = (this.maxSection - this.minSection) + 1;
+            final int chunkY = ((index / (5*5)) % (ySections + 2 + 2)) - this.chunkOffsetY;
+            if ((nibble != null && nibble.updateVisible()) || this.notifyUpdateCache[index]) {
+                lightAccess.onLightUpdate(this.skylightPropagator ? LightLayer.SKY : LightLayer.BLOCK, SectionPos.of(chunkX, chunkY, chunkZ));
+            }
+        }
+    }
+
+    protected final void destroyCaches() {
+        Arrays.fill(this.sectionCache, null);
+        Arrays.fill(this.nibbleCache, null);
+        Arrays.fill(this.chunkCache, null);
+        Arrays.fill(this.emptinessMapCache, null);
+        if (this.isClientSide) {
+            Arrays.fill(this.notifyUpdateCache, false);
+        }
+    }
+
+    protected final BlockState getBlockState(final int worldX, final int worldY, final int worldZ) {
+        final LevelChunkSection section = this.sectionCache[(worldX >> 4) + 5 * (worldZ >> 4) + (5 * 5) * (worldY >> 4) + this.chunkSectionIndexOffset];
+
+        if (section != null) {
+            return section.hasOnlyAir() ? AIR_BLOCK_STATE : section.getBlockState(worldX & 15, worldY & 15, worldZ & 15);
+        }
+
+        return AIR_BLOCK_STATE;
+    }
+
+    protected final BlockState getBlockState(final int sectionIndex, final int localIndex) {
+        final LevelChunkSection section = this.sectionCache[sectionIndex];
+
+        if (section != null) {
+            return section.hasOnlyAir() ? AIR_BLOCK_STATE : section.states.get(localIndex);
+        }
+
+        return AIR_BLOCK_STATE;
+    }
+
+    protected final int getLightLevel(final int worldX, final int worldY, final int worldZ) {
+        final SWMRNibbleArray nibble = this.nibbleCache[(worldX >> 4) + 5 * (worldZ >> 4) + (5 * 5) * (worldY >> 4) + this.chunkSectionIndexOffset];
+
+        return nibble == null ? 0 : nibble.getUpdating((worldX & 15) | ((worldZ & 15) << 4) | ((worldY & 15) << 8));
+    }
+
+    protected final int getLightLevel(final int sectionIndex, final int localIndex) {
+        final SWMRNibbleArray nibble = this.nibbleCache[sectionIndex];
+
+        return nibble == null ? 0 : nibble.getUpdating(localIndex);
+    }
+
+    protected final void setLightLevel(final int worldX, final int worldY, final int worldZ, final int level) {
+        final int sectionIndex = (worldX >> 4) + 5 * (worldZ >> 4) + (5 * 5) * (worldY >> 4) + this.chunkSectionIndexOffset;
+        final SWMRNibbleArray nibble = this.nibbleCache[sectionIndex];
+
+        if (nibble != null) {
+            nibble.set((worldX & 15) | ((worldZ & 15) << 4) | ((worldY & 15) << 8), level);
+            if (this.isClientSide) {
+                int cx1 = (worldX - 1) >> 4;
+                int cx2 = (worldX + 1) >> 4;
+                int cy1 = (worldY - 1) >> 4;
+                int cy2 = (worldY + 1) >> 4;
+                int cz1 = (worldZ - 1) >> 4;
+                int cz2 = (worldZ + 1) >> 4;
+                for (int x = cx1; x <= cx2; ++x) {
+                    for (int y = cy1; y <= cy2; ++y) {
+                        for (int z = cz1; z <= cz2; ++z) {
+                            this.notifyUpdateCache[x + 5 * z + (5 * 5) * y + this.chunkSectionIndexOffset] = true;
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    protected final void postLightUpdate(final int worldX, final int worldY, final int worldZ) {
+        if (this.isClientSide) {
+            int cx1 = (worldX - 1) >> 4;
+            int cx2 = (worldX + 1) >> 4;
+            int cy1 = (worldY - 1) >> 4;
+            int cy2 = (worldY + 1) >> 4;
+            int cz1 = (worldZ - 1) >> 4;
+            int cz2 = (worldZ + 1) >> 4;
+            for (int x = cx1; x <= cx2; ++x) {
+                for (int y = cy1; y <= cy2; ++y) {
+                    for (int z = cz1; z <= cz2; ++z) {
+                        this.notifyUpdateCache[x + (5 * z) + (5 * 5 * y) + this.chunkSectionIndexOffset] = true;
+                    }
+                }
+            }
+        }
+    }
+
+    protected final void setLightLevel(final int sectionIndex, final int localIndex, final int worldX, final int worldY, final int worldZ, final int level) {
+        final SWMRNibbleArray nibble = this.nibbleCache[sectionIndex];
+
+        if (nibble != null) {
+            nibble.set(localIndex, level);
+            if (this.isClientSide) {
+                int cx1 = (worldX - 1) >> 4;
+                int cx2 = (worldX + 1) >> 4;
+                int cy1 = (worldY - 1) >> 4;
+                int cy2 = (worldY + 1) >> 4;
+                int cz1 = (worldZ - 1) >> 4;
+                int cz2 = (worldZ + 1) >> 4;
+                for (int x = cx1; x <= cx2; ++x) {
+                    for (int y = cy1; y <= cy2; ++y) {
+                        for (int z = cz1; z <= cz2; ++z) {
+                            this.notifyUpdateCache[x + (5 * z) + (5 * 5 * y) + this.chunkSectionIndexOffset] = true;
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    protected final boolean[] getEmptinessMap(final int chunkX, final int chunkZ) {
+        return this.emptinessMapCache[chunkX + 5*chunkZ + this.chunkIndexOffset];
+    }
+
+    protected final void setEmptinessMapCache(final int chunkX, final int chunkZ, final boolean[] emptinessMap) {
+        this.emptinessMapCache[chunkX + 5*chunkZ + this.chunkIndexOffset] = emptinessMap;
+    }
+
+    public static SWMRNibbleArray[] getFilledEmptyLight(final LevelHeightAccessor world) {
+        return getFilledEmptyLight(WorldUtil.getTotalLightSections(world));
+    }
+
+    private static SWMRNibbleArray[] getFilledEmptyLight(final int totalLightSections) {
+        final SWMRNibbleArray[] ret = new SWMRNibbleArray[totalLightSections];
+
+        for (int i = 0, len = ret.length; i < len; ++i) {
+            ret[i] = new SWMRNibbleArray(null, true);
+        }
+
+        return ret;
+    }
+
+    protected abstract boolean[] getEmptinessMap(final ChunkAccess chunk);
+
+    protected abstract void setEmptinessMap(final ChunkAccess chunk, final boolean[] to);
+
+    protected abstract SWMRNibbleArray[] getNibblesOnChunk(final ChunkAccess chunk);
+
+    protected abstract void setNibbles(final ChunkAccess chunk, final SWMRNibbleArray[] to);
+
+    protected abstract boolean canUseChunk(final ChunkAccess chunk);
+
+    public final void blocksChangedInChunk(final LightChunkGetter lightAccess, final int chunkX, final int chunkZ,
+                                           final Set<BlockPos> positions, final Boolean[] changedSections) {
+        this.setupCaches(lightAccess, chunkX * 16 + 7, 128, chunkZ * 16 + 7, true, true);
+        try {
+            final ChunkAccess chunk = this.getChunkInCache(chunkX, chunkZ);
+            if (chunk == null) {
+                return;
+            }
+            if (changedSections != null) {
+                final boolean[] ret = this.handleEmptySectionChanges(lightAccess, chunk, changedSections, false);
+                if (ret != null) {
+                    this.setEmptinessMap(chunk, ret);
+                }
+            }
+            if (!positions.isEmpty()) {
+                this.propagateBlockChanges(lightAccess, chunk, positions);
+            }
+            this.updateVisible(lightAccess);
+        } finally {
+            this.destroyCaches();
+        }
+    }
+
+    // subclasses should not initialise caches, as this will always be done by the super call
+    // subclasses should not invoke updateVisible, as this will always be done by the super call
+    protected abstract void propagateBlockChanges(final LightChunkGetter lightAccess, final ChunkAccess atChunk, final Set<BlockPos> positions);
+
+    protected abstract void checkBlock(final LightChunkGetter lightAccess, final int worldX, final int worldY, final int worldZ);
+
+    // if ret > expect, then the real value is at least ret (early returns if ret > expect, rather than calculating actual)
+    // if ret == expect, then expect is the correct light value for pos
+    // if ret < expect, then ret is the real light value
+    protected abstract int calculateLightValue(final LightChunkGetter lightAccess, final int worldX, final int worldY, final int worldZ,
+                                               final int expect);
+
+    protected final int[] chunkCheckDelayedUpdatesCenter = new int[16 * 16];
+    protected final int[] chunkCheckDelayedUpdatesNeighbour = new int[16 * 16];
+
+    protected void checkChunkEdge(final LightChunkGetter lightAccess, final ChunkAccess chunk,
+                                  final int chunkX, final int chunkY, final int chunkZ) {
+        final SWMRNibbleArray currNibble = this.getNibbleFromCache(chunkX, chunkY, chunkZ);
+        if (currNibble == null) {
+            return;
+        }
+
+        for (final AxisDirection direction : ONLY_HORIZONTAL_DIRECTIONS) {
+            final int neighbourOffX = direction.x;
+            final int neighbourOffZ = direction.z;
+
+            final SWMRNibbleArray neighbourNibble = this.getNibbleFromCache(chunkX + neighbourOffX,
+                    chunkY, chunkZ + neighbourOffZ);
+
+            if (neighbourNibble == null) {
+                continue;
+            }
+
+            if (!currNibble.isInitialisedUpdating() && !neighbourNibble.isInitialisedUpdating()) {
+                // both are zero, nothing to check.
+                continue;
+            }
+
+            // this chunk
+            final int incX;
+            final int incZ;
+            final int startX;
+            final int startZ;
+
+            if (neighbourOffX != 0) {
+                // x direction
+                incX = 0;
+                incZ = 1;
+
+                if (direction.x < 0) {
+                    // negative
+                    startX = chunkX << 4;
+                } else {
+                    startX = chunkX << 4 | 15;
+                }
+                startZ = chunkZ << 4;
+            } else {
+                // z direction
+                incX = 1;
+                incZ = 0;
+
+                if (neighbourOffZ < 0) {
+                    // negative
+                    startZ = chunkZ << 4;
+                } else {
+                    startZ = chunkZ << 4 | 15;
+                }
+                startX = chunkX << 4;
+            }
+
+            int centerDelayedChecks = 0;
+            int neighbourDelayedChecks = 0;
+            for (int currY = chunkY << 4, maxY = currY | 15; currY <= maxY; ++currY) {
+                for (int i = 0, currX = startX, currZ = startZ; i < 16; ++i, currX += incX, currZ += incZ) {
+                    final int neighbourX = currX + neighbourOffX;
+                    final int neighbourZ = currZ + neighbourOffZ;
+
+                    final int currentIndex = (currX & 15) |
+                            ((currZ & 15)) << 4 |
+                            ((currY & 15) << 8);
+                    final int currentLevel = currNibble.getUpdating(currentIndex);
+
+                    final int neighbourIndex =
+                            (neighbourX & 15) |
+                            ((neighbourZ & 15)) << 4 |
+                            ((currY & 15) << 8);
+                    final int neighbourLevel = neighbourNibble.getUpdating(neighbourIndex);
+
+                    // the checks are delayed because the checkBlock method clobbers light values - which then
+                    // affect later calculate light value operations. While they don't affect it in a behaviourly significant
+                    // way, they do have a negative performance impact due to simply queueing more values
+
+                    if (this.calculateLightValue(lightAccess, currX, currY, currZ, currentLevel) != currentLevel) {
+                        this.chunkCheckDelayedUpdatesCenter[centerDelayedChecks++] = currentIndex;
+                    }
+
+                    if (this.calculateLightValue(lightAccess, neighbourX, currY, neighbourZ, neighbourLevel) != neighbourLevel) {
+                        this.chunkCheckDelayedUpdatesNeighbour[neighbourDelayedChecks++] = neighbourIndex;
+                    }
+                }
+            }
+
+            final int currentChunkOffX = chunkX << 4;
+            final int currentChunkOffZ = chunkZ << 4;
+            final int neighbourChunkOffX = (chunkX + direction.x) << 4;
+            final int neighbourChunkOffZ = (chunkZ + direction.z) << 4;
+            final int chunkOffY = chunkY << 4;
+            for (int i = 0, len = Math.max(centerDelayedChecks, neighbourDelayedChecks); i < len; ++i) {
+                // try to queue neighbouring data together
+                // index = x | (z << 4) | (y << 8)
+                if (i < centerDelayedChecks) {
+                    final int value = this.chunkCheckDelayedUpdatesCenter[i];
+                    this.checkBlock(lightAccess, currentChunkOffX | (value & 15),
+                            chunkOffY | (value >>> 8),
+                            currentChunkOffZ | ((value >>> 4) & 0xF));
+                }
+                if (i < neighbourDelayedChecks) {
+                    final int value = this.chunkCheckDelayedUpdatesNeighbour[i];
+                    this.checkBlock(lightAccess, neighbourChunkOffX | (value & 15),
+                            chunkOffY | (value >>> 8),
+                            neighbourChunkOffZ | ((value >>> 4) & 0xF));
+                }
+            }
+        }
+    }
+
+    protected void checkChunkEdges(final LightChunkGetter lightAccess, final ChunkAccess chunk, final ShortCollection sections) {
+        final ChunkPos chunkPos = chunk.getPos();
+        final int chunkX = chunkPos.x;
+        final int chunkZ = chunkPos.z;
+
+        for (final ShortIterator iterator = sections.iterator(); iterator.hasNext();) {
+            this.checkChunkEdge(lightAccess, chunk, chunkX, iterator.nextShort(), chunkZ);
+        }
+
+        this.performLightDecrease(lightAccess);
+    }
+
+    // subclasses should not initialise caches, as this will always be done by the super call
+    // subclasses should not invoke updateVisible, as this will always be done by the super call
+    // verifies that light levels on this chunks edges are consistent with this chunk's neighbours
+    // edges. if they are not, they are decreased (effectively performing the logic in checkBlock).
+    // This does not resolve skylight source problems.
+    protected void checkChunkEdges(final LightChunkGetter lightAccess, final ChunkAccess chunk, final int fromSection, final int toSection) {
+        final ChunkPos chunkPos = chunk.getPos();
+        final int chunkX = chunkPos.x;
+        final int chunkZ = chunkPos.z;
+
+        for (int currSectionY = toSection; currSectionY >= fromSection; --currSectionY) {
+            this.checkChunkEdge(lightAccess, chunk, chunkX, currSectionY, chunkZ);
+        }
+
+        this.performLightDecrease(lightAccess);
+    }
+
+    // pulls light from neighbours, and adds them into the increase queue. does not actually propagate.
+    protected final void propagateNeighbourLevels(final LightChunkGetter lightAccess, final ChunkAccess chunk, final int fromSection, final int toSection) {
+        final ChunkPos chunkPos = chunk.getPos();
+        final int chunkX = chunkPos.x;
+        final int chunkZ = chunkPos.z;
+
+        for (int currSectionY = toSection; currSectionY >= fromSection; --currSectionY) {
+            final SWMRNibbleArray currNibble = this.getNibbleFromCache(chunkX, currSectionY, chunkZ);
+            if (currNibble == null) {
+                continue;
+            }
+            for (final AxisDirection direction : ONLY_HORIZONTAL_DIRECTIONS) {
+                final int neighbourOffX = direction.x;
+                final int neighbourOffZ = direction.z;
+
+                final SWMRNibbleArray neighbourNibble = this.getNibbleFromCache(chunkX + neighbourOffX,
+                        currSectionY, chunkZ + neighbourOffZ);
+
+                if (neighbourNibble == null || !neighbourNibble.isInitialisedUpdating()) {
+                    // can't pull from 0
+                    continue;
+                }
+
+                // neighbour chunk
+                final int incX;
+                final int incZ;
+                final int startX;
+                final int startZ;
+
+                if (neighbourOffX != 0) {
+                    // x direction
+                    incX = 0;
+                    incZ = 1;
+
+                    if (direction.x < 0) {
+                        // negative
+                        startX = (chunkX << 4) - 1;
+                    } else {
+                        startX = (chunkX << 4) + 16;
+                    }
+                    startZ = chunkZ << 4;
+                } else {
+                    // z direction
+                    incX = 1;
+                    incZ = 0;
+
+                    if (neighbourOffZ < 0) {
+                        // negative
+                        startZ = (chunkZ << 4) - 1;
+                    } else {
+                        startZ = (chunkZ << 4) + 16;
+                    }
+                    startX = chunkX << 4;
+                }
+
+                final long propagateDirection = 1L << direction.getOpposite().ordinal(); // we only want to check in this direction towards this chunk
+                final int encodeOffset = this.coordinateOffset;
+
+                for (int currY = currSectionY << 4, maxY = currY | 15; currY <= maxY; ++currY) {
+                    for (int i = 0, currX = startX, currZ = startZ; i < 16; ++i, currX += incX, currZ += incZ) {
+                        final int level = neighbourNibble.getUpdating(
+                                (currX & 15)
+                                        | ((currZ & 15) << 4)
+                                        | ((currY & 15) << 8)
+                        );
+
+                        if (level <= 1) {
+                            // nothing to propagate
+                            continue;
+                        }
+
+                        this.appendToIncreaseQueue(
+                                ((currX + (currZ << 6) + (currY << (6 + 6)) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                        | ((level & 0xFL) << (6 + 6 + 16))
+                                        | (propagateDirection << (6 + 6 + 16 + 4))
+                                        | FLAG_HAS_SIDED_TRANSPARENT_BLOCKS // don't know if the current block is transparent, must check.
+                        );
+                    }
+                }
+            }
+        }
+    }
+
+    public static Boolean[] getEmptySectionsForChunk(final ChunkAccess chunk) {
+        final LevelChunkSection[] sections = chunk.getSections();
+        final Boolean[] ret = new Boolean[sections.length];
+
+        for (int i = 0; i < sections.length; ++i) {
+            if (sections[i] == null || sections[i].hasOnlyAir()) {
+                ret[i] = Boolean.TRUE;
+            } else {
+                ret[i] = Boolean.FALSE;
+            }
+        }
+
+        return ret;
+    }
+
+    public final void forceHandleEmptySectionChanges(final LightChunkGetter lightAccess, final ChunkAccess chunk, final Boolean[] emptinessChanges) {
+        final int chunkX = chunk.getPos().x;
+        final int chunkZ = chunk.getPos().z;
+        this.setupCaches(lightAccess, chunkX * 16 + 7, 128, chunkZ * 16 + 7, true, true);
+        try {
+            // force current chunk into cache
+            this.setChunkInCache(chunkX, chunkZ, chunk);
+            this.setBlocksForChunkInCache(chunkX, chunkZ, chunk.getSections());
+            this.setNibblesForChunkInCache(chunkX, chunkZ, this.getNibblesOnChunk(chunk));
+            this.setEmptinessMapCache(chunkX, chunkZ, this.getEmptinessMap(chunk));
+
+            final boolean[] ret = this.handleEmptySectionChanges(lightAccess, chunk, emptinessChanges, false);
+            if (ret != null) {
+                this.setEmptinessMap(chunk, ret);
+            }
+            this.updateVisible(lightAccess);
+        } finally {
+            this.destroyCaches();
+        }
+    }
+
+    public final void handleEmptySectionChanges(final LightChunkGetter lightAccess, final int chunkX, final int chunkZ,
+                                                final Boolean[] emptinessChanges) {
+        this.setupCaches(lightAccess, chunkX * 16 + 7, 128, chunkZ * 16 + 7, true, true);
+        try {
+            final ChunkAccess chunk = this.getChunkInCache(chunkX, chunkZ);
+            if (chunk == null) {
+                return;
+            }
+            final boolean[] ret = this.handleEmptySectionChanges(lightAccess, chunk, emptinessChanges, false);
+            if (ret != null) {
+                this.setEmptinessMap(chunk, ret);
+            }
+            this.updateVisible(lightAccess);
+        } finally {
+            this.destroyCaches();
+        }
+    }
+
+    protected abstract void initNibble(final int chunkX, final int chunkY, final int chunkZ, final boolean extrude, final boolean initRemovedNibbles);
+
+    protected abstract void setNibbleNull(final int chunkX, final int chunkY, final int chunkZ);
+
+    // subclasses should not initialise caches, as this will always be done by the super call
+    // subclasses should not invoke updateVisible, as this will always be done by the super call
+    // subclasses are guaranteed that this is always called before a changed block set
+    // newChunk specifies whether the changes describe a "first load" of a chunk or changes to existing, already loaded chunks
+    // rets non-null when the emptiness map changed and needs to be updated
+    protected final boolean[] handleEmptySectionChanges(final LightChunkGetter lightAccess, final ChunkAccess chunk,
+                                                        final Boolean[] emptinessChanges, final boolean unlit) {
+        final Level world = (Level)lightAccess.getLevel();
+        final int chunkX = chunk.getPos().x;
+        final int chunkZ = chunk.getPos().z;
+
+        boolean[] chunkEmptinessMap = this.getEmptinessMap(chunkX, chunkZ);
+        boolean[] ret = null;
+        final boolean needsInit = unlit || chunkEmptinessMap == null;
+        if (needsInit) {
+            this.setEmptinessMapCache(chunkX, chunkZ, ret = chunkEmptinessMap = new boolean[WorldUtil.getTotalSections(world)]);
+        }
+
+        // update emptiness map
+        for (int sectionIndex = (emptinessChanges.length - 1); sectionIndex >= 0; --sectionIndex) {
+            Boolean valueBoxed = emptinessChanges[sectionIndex];
+            if (valueBoxed == null) {
+                if (!needsInit) {
+                    continue;
+                }
+                final LevelChunkSection section = this.getChunkSection(chunkX, sectionIndex + this.minSection, chunkZ);
+                emptinessChanges[sectionIndex] = valueBoxed = section == null || section.hasOnlyAir() ? Boolean.TRUE : Boolean.FALSE;
+            }
+            chunkEmptinessMap[sectionIndex] = valueBoxed.booleanValue();
+        }
+
+        // now init neighbour nibbles
+        for (int sectionIndex = (emptinessChanges.length - 1); sectionIndex >= 0; --sectionIndex) {
+            final Boolean valueBoxed = emptinessChanges[sectionIndex];
+            final int sectionY = sectionIndex + this.minSection;
+            if (valueBoxed == null) {
+                continue;
+            }
+
+            final boolean empty = valueBoxed.booleanValue();
+
+            if (empty) {
+                continue;
+            }
+
+            for (int dz = -1; dz <= 1; ++dz) {
+                for (int dx = -1; dx <= 1; ++dx) {
+                    // if we're not empty, we also need to initialise nibbles
+                    // note: if we're unlit, we absolutely do not want to extrude, as light data isn't set up
+                    final boolean extrude = (dx | dz) != 0 || !unlit;
+                    for (int dy = 1; dy >= -1; --dy) {
+                        this.initNibble(dx + chunkX, dy + sectionY, dz + chunkZ, extrude, false);
+                    }
+                }
+            }
+        }
+
+        // check for de-init and lazy-init
+        // lazy init is when chunks are being lit, so at the time they weren't loaded when their neighbours were running
+        // init checks.
+        for (int dz = -1; dz <= 1; ++dz) {
+            for (int dx = -1; dx <= 1; ++dx) {
+                // does this neighbour have 1 radius loaded?
+                boolean neighboursLoaded = true;
+                neighbour_loaded_search:
+                for (int dz2 = -1; dz2 <= 1; ++dz2) {
+                    for (int dx2 = -1; dx2 <= 1; ++dx2) {
+                        if (this.getEmptinessMap(dx + dx2 + chunkX, dz + dz2 + chunkZ) == null) {
+                            neighboursLoaded = false;
+                            break neighbour_loaded_search;
+                        }
+                    }
+                }
+
+                for (int sectionY = this.maxLightSection; sectionY >= this.minLightSection; --sectionY) {
+                    // check neighbours to see if we need to de-init this one
+                    boolean allEmpty = true;
+                    neighbour_search:
+                    for (int dy2 = -1; dy2 <= 1; ++dy2) {
+                        for (int dz2 = -1; dz2 <= 1; ++dz2) {
+                            for (int dx2 = -1; dx2 <= 1; ++dx2) {
+                                final int y = sectionY + dy2;
+                                if (y < this.minSection || y > this.maxSection) {
+                                    // empty
+                                    continue;
+                                }
+                                final boolean[] emptinessMap = this.getEmptinessMap(dx + dx2 + chunkX, dz + dz2 + chunkZ);
+                                if (emptinessMap != null) {
+                                    if (!emptinessMap[y - this.minSection]) {
+                                        allEmpty = false;
+                                        break neighbour_search;
+                                    }
+                                } else {
+                                    final LevelChunkSection section = this.getChunkSection(dx + dx2 + chunkX, y, dz + dz2 + chunkZ);
+                                    if (section != null && !section.hasOnlyAir()) {
+                                        allEmpty = false;
+                                        break neighbour_search;
+                                    }
+                                }
+                            }
+                        }
+                    }
+
+                    if (allEmpty & neighboursLoaded) {
+                        // can only de-init when neighbours are loaded
+                        // de-init is fine to delay, as de-init is just an optimisation - it's not required for lighting
+                        // to be correct
+
+                        // all were empty, so de-init
+                        this.setNibbleNull(dx + chunkX, sectionY, dz + chunkZ);
+                    } else if (!allEmpty) {
+                        // must init
+                        final boolean extrude = (dx | dz) != 0 || !unlit;
+                        this.initNibble(dx + chunkX, sectionY, dz + chunkZ, extrude, false);
+                    }
+                }
+            }
+        }
+
+        return ret;
+    }
+
+    public final void checkChunkEdges(final LightChunkGetter lightAccess, final int chunkX, final int chunkZ) {
+        this.setupCaches(lightAccess, chunkX * 16 + 7, 128, chunkZ * 16 + 7, true, false);
+        try {
+            final ChunkAccess chunk = this.getChunkInCache(chunkX, chunkZ);
+            if (chunk == null) {
+                return;
+            }
+            this.checkChunkEdges(lightAccess, chunk, this.minLightSection, this.maxLightSection);
+            this.updateVisible(lightAccess);
+        } finally {
+            this.destroyCaches();
+        }
+    }
+
+    public final void checkChunkEdges(final LightChunkGetter lightAccess, final int chunkX, final int chunkZ, final ShortCollection sections) {
+        this.setupCaches(lightAccess, chunkX * 16 + 7, 128, chunkZ * 16 + 7, true, false);
+        try {
+            final ChunkAccess chunk = this.getChunkInCache(chunkX, chunkZ);
+            if (chunk == null) {
+                return;
+            }
+            this.checkChunkEdges(lightAccess, chunk, sections);
+            this.updateVisible(lightAccess);
+        } finally {
+            this.destroyCaches();
+        }
+    }
+
+    // subclasses should not initialise caches, as this will always be done by the super call
+    // subclasses should not invoke updateVisible, as this will always be done by the super call
+    // needsEdgeChecks applies when possibly loading vanilla data, which means we need to validate the current
+    // chunks light values with respect to neighbours
+    // subclasses should note that the emptiness changes are propagated BEFORE this is called, so this function
+    // does not need to detect empty chunks itself (and it should do no handling for them either!)
+    protected abstract void lightChunk(final LightChunkGetter lightAccess, final ChunkAccess chunk, final boolean needsEdgeChecks);
+
+    public final void light(final LightChunkGetter lightAccess, final ChunkAccess chunk, final Boolean[] emptySections) {
+        final int chunkX = chunk.getPos().x;
+        final int chunkZ = chunk.getPos().z;
+        this.setupCaches(lightAccess, chunkX * 16 + 7, 128, chunkZ * 16 + 7, true, true);
+
+        try {
+            final SWMRNibbleArray[] nibbles = getFilledEmptyLight(this.maxLightSection - this.minLightSection + 1);
+            // force current chunk into cache
+            this.setChunkInCache(chunkX, chunkZ, chunk);
+            this.setBlocksForChunkInCache(chunkX, chunkZ, chunk.getSections());
+            this.setNibblesForChunkInCache(chunkX, chunkZ, nibbles);
+            this.setEmptinessMapCache(chunkX, chunkZ, this.getEmptinessMap(chunk));
+
+            final boolean[] ret = this.handleEmptySectionChanges(lightAccess, chunk, emptySections, true);
+            if (ret != null) {
+                this.setEmptinessMap(chunk, ret);
+            }
+            this.lightChunk(lightAccess, chunk, true);
+            this.setNibbles(chunk, nibbles);
+            this.updateVisible(lightAccess);
+        } finally {
+            this.destroyCaches();
+        }
+    }
+
+    public final void relightChunks(final LightChunkGetter lightAccess, final Set<ChunkPos> chunks,
+                                    final Consumer<ChunkPos> chunkLightCallback, final IntConsumer onComplete) {
+        // it's recommended for maximum performance that the set is ordered according to a BFS from the center of
+        // the region of chunks to relight
+        // it's required that tickets are added for each chunk to keep them loaded
+        final Long2ObjectOpenHashMap<SWMRNibbleArray[]> nibblesByChunk = new Long2ObjectOpenHashMap<>();
+        final Long2ObjectOpenHashMap<boolean[]> emptinessMapByChunk = new Long2ObjectOpenHashMap<>();
+
+        final int[] neighbourLightOrder = new int[] {
+                // d = 0
+                0, 0,
+                // d = 1
+                -1, 0,
+                0, -1,
+                1, 0,
+                0, 1,
+                // d = 2
+                -1, 1,
+                1, 1,
+                -1, -1,
+                1, -1,
+        };
+
+        int lightCalls = 0;
+
+        for (final ChunkPos chunkPos : chunks) {
+            final int chunkX = chunkPos.x;
+            final int chunkZ = chunkPos.z;
+            final ChunkAccess chunk = (ChunkAccess)lightAccess.getChunkForLighting(chunkX, chunkZ);
+            if (chunk == null || !this.canUseChunk(chunk)) {
+                throw new IllegalStateException();
+            }
+
+            for (int i = 0, len = neighbourLightOrder.length; i < len; i += 2) {
+                final int dx = neighbourLightOrder[i];
+                final int dz = neighbourLightOrder[i + 1];
+                final int neighbourX = dx + chunkX;
+                final int neighbourZ = dz + chunkZ;
+
+                final ChunkAccess neighbour = (ChunkAccess)lightAccess.getChunkForLighting(neighbourX, neighbourZ);
+                if (neighbour == null || !this.canUseChunk(neighbour)) {
+                    continue;
+                }
+
+                if (nibblesByChunk.get(CoordinateUtils.getChunkKey(neighbourX, neighbourZ)) != null) {
+                    // lit already called for neighbour, no need to light it now
+                    continue;
+                }
+
+                // light neighbour chunk
+                this.setupEncodeOffset(neighbourX * 16 + 7, 128, neighbourZ * 16 + 7);
+                try {
+                    // insert all neighbouring chunks for this neighbour that we have data for
+                    for (int dz2 = -1; dz2 <= 1; ++dz2) {
+                        for (int dx2 = -1; dx2 <= 1; ++dx2) {
+                            final int neighbourX2 = neighbourX + dx2;
+                            final int neighbourZ2 = neighbourZ + dz2;
+                            final long key = CoordinateUtils.getChunkKey(neighbourX2, neighbourZ2);
+                            final ChunkAccess neighbour2 = (ChunkAccess)lightAccess.getChunkForLighting(neighbourX2, neighbourZ2);
+                            if (neighbour2 == null || !this.canUseChunk(neighbour2)) {
+                                continue;
+                            }
+
+                            final SWMRNibbleArray[] nibbles = nibblesByChunk.get(key);
+                            if (nibbles == null) {
+                                // we haven't lit this chunk
+                                continue;
+                            }
+
+                            this.setChunkInCache(neighbourX2, neighbourZ2, neighbour2);
+                            this.setBlocksForChunkInCache(neighbourX2, neighbourZ2, neighbour2.getSections());
+                            this.setNibblesForChunkInCache(neighbourX2, neighbourZ2, nibbles);
+                            this.setEmptinessMapCache(neighbourX2, neighbourZ2, emptinessMapByChunk.get(key));
+                        }
+                    }
+
+                    final long key = CoordinateUtils.getChunkKey(neighbourX, neighbourZ);
+
+                    // now insert the neighbour chunk and light it
+                    final SWMRNibbleArray[] nibbles = getFilledEmptyLight(this.world);
+                    nibblesByChunk.put(key, nibbles);
+
+                    this.setChunkInCache(neighbourX, neighbourZ, neighbour);
+                    this.setBlocksForChunkInCache(neighbourX, neighbourZ, neighbour.getSections());
+                    this.setNibblesForChunkInCache(neighbourX, neighbourZ, nibbles);
+
+                    final boolean[] neighbourEmptiness = this.handleEmptySectionChanges(lightAccess, neighbour, getEmptySectionsForChunk(neighbour), true);
+                    emptinessMapByChunk.put(key, neighbourEmptiness);
+                    if (chunks.contains(new ChunkPos(neighbourX, neighbourZ))) {
+                        this.setEmptinessMap(neighbour, neighbourEmptiness);
+                    }
+
+                    this.lightChunk(lightAccess, neighbour, false);
+                } finally {
+                    this.destroyCaches();
+                }
+            }
+
+            // done lighting all neighbours, so the chunk is now fully lit
+
+            // make sure nibbles are fully updated before calling back
+            final SWMRNibbleArray[] nibbles = nibblesByChunk.get(CoordinateUtils.getChunkKey(chunkX, chunkZ));
+            for (final SWMRNibbleArray nibble : nibbles) {
+                nibble.updateVisible();
+            }
+
+            this.setNibbles(chunk, nibbles);
+
+            for (int y = this.minLightSection; y <= this.maxLightSection; ++y) {
+                lightAccess.onLightUpdate(this.skylightPropagator ? LightLayer.SKY : LightLayer.BLOCK, SectionPos.of(chunkX, y, chunkX));
+            }
+
+            // now do callback
+            if (chunkLightCallback != null) {
+                chunkLightCallback.accept(chunkPos);
+            }
+            ++lightCalls;
+        }
+
+        if (onComplete != null) {
+            onComplete.accept(lightCalls);
+        }
+    }
+
+    // contains:
+    // lower (6 + 6 + 16) = 28 bits: encoded coordinate position (x | (z << 6) | (y << (6 + 6))))
+    // next 4 bits: propagated light level (0, 15]
+    // next 6 bits: propagation direction bitset
+    // next 24 bits: unused
+    // last 3 bits: state flags
+    // state flags:
+    // whether the increase propagator needs to write the propagated level to the position, used to avoid cascading light
+    // updates for block sources
+    protected static final long FLAG_WRITE_LEVEL = Long.MIN_VALUE >>> 2;
+    // whether the propagation needs to check if its current level is equal to the expected level
+    // used only in increase propagation
+    protected static final long FLAG_RECHECK_LEVEL = Long.MIN_VALUE >>> 1;
+    // whether the propagation needs to consider if its block is conditionally transparent
+    protected static final long FLAG_HAS_SIDED_TRANSPARENT_BLOCKS = Long.MIN_VALUE;
+
+    protected long[] increaseQueue = new long[16 * 16 * 16];
+    protected int increaseQueueInitialLength;
+    protected long[] decreaseQueue = new long[16 * 16 * 16];
+    protected int decreaseQueueInitialLength;
+
+    protected final long[] resizeIncreaseQueue() {
+        return this.increaseQueue = Arrays.copyOf(this.increaseQueue, this.increaseQueue.length * 2);
+    }
+
+    protected final long[] resizeDecreaseQueue() {
+        return this.decreaseQueue = Arrays.copyOf(this.decreaseQueue, this.decreaseQueue.length * 2);
+    }
+
+    protected final void appendToIncreaseQueue(final long value) {
+        final int idx = this.increaseQueueInitialLength++;
+        long[] queue = this.increaseQueue;
+        if (idx >= queue.length) {
+            queue = this.resizeIncreaseQueue();
+            queue[idx] = value;
+        } else {
+            queue[idx] = value;
+        }
+    }
+
+    protected final void appendToDecreaseQueue(final long value) {
+        final int idx = this.decreaseQueueInitialLength++;
+        long[] queue = this.decreaseQueue;
+        if (idx >= queue.length) {
+            queue = this.resizeDecreaseQueue();
+            queue[idx] = value;
+        } else {
+            queue[idx] = value;
+        }
+    }
+
+    protected static final AxisDirection[][] OLD_CHECK_DIRECTIONS = new AxisDirection[1 << 6][];
+    protected static final int ALL_DIRECTIONS_BITSET = (1 << 6) - 1;
+    static {
+        for (int i = 0; i < OLD_CHECK_DIRECTIONS.length; ++i) {
+            final List<AxisDirection> directions = new ArrayList<>();
+            for (int bitset = i, len = Integer.bitCount(i), index = 0; index < len; ++index, bitset ^= IntegerUtil.getTrailingBit(bitset)) {
+                directions.add(AXIS_DIRECTIONS[IntegerUtil.trailingZeros(bitset)]);
+            }
+            OLD_CHECK_DIRECTIONS[i] = directions.toArray(new AxisDirection[0]);
+        }
+    }
+
+    protected final void performLightIncrease(final LightChunkGetter lightAccess) {
+        final BlockGetter world = lightAccess.getLevel();
+        long[] queue = this.increaseQueue;
+        int queueReadIndex = 0;
+        int queueLength = this.increaseQueueInitialLength;
+        this.increaseQueueInitialLength = 0;
+        final int decodeOffsetX = -this.encodeOffsetX;
+        final int decodeOffsetY = -this.encodeOffsetY;
+        final int decodeOffsetZ = -this.encodeOffsetZ;
+        final int encodeOffset = this.coordinateOffset;
+        final int sectionOffset = this.chunkSectionIndexOffset;
+
+        while (queueReadIndex < queueLength) {
+            final long queueValue = queue[queueReadIndex++];
+
+            final int posX = ((int)queueValue & 63) + decodeOffsetX;
+            final int posZ = (((int)queueValue >>> 6) & 63) + decodeOffsetZ;
+            final int posY = (((int)queueValue >>> 12) & ((1 << 16) - 1)) + decodeOffsetY;
+            final int propagatedLightLevel = (int)((queueValue >>> (6 + 6 + 16)) & 0xFL);
+            final AxisDirection[] checkDirections = OLD_CHECK_DIRECTIONS[(int)((queueValue >>> (6 + 6 + 16 + 4)) & 63L)];
+
+            if ((queueValue & FLAG_RECHECK_LEVEL) != 0L) {
+                if (this.getLightLevel(posX, posY, posZ) != propagatedLightLevel) {
+                    // not at the level we expect, so something changed.
+                    continue;
+                }
+            } else if ((queueValue & FLAG_WRITE_LEVEL) != 0L) {
+                // these are used to restore block sources after a propagation decrease
+                this.setLightLevel(posX, posY, posZ, propagatedLightLevel);
+            }
+
+            if ((queueValue & FLAG_HAS_SIDED_TRANSPARENT_BLOCKS) == 0L) {
+                // we don't need to worry about our state here.
+                for (final AxisDirection propagate : checkDirections) {
+                    final int offX = posX + propagate.x;
+                    final int offY = posY + propagate.y;
+                    final int offZ = posZ + propagate.z;
+
+                    final int sectionIndex = (offX >> 4) + 5 * (offZ >> 4) + (5 * 5) * (offY >> 4) + sectionOffset;
+                    final int localIndex = (offX & 15) | ((offZ & 15) << 4) | ((offY & 15) << 8);
+
+                    final SWMRNibbleArray currentNibble = this.nibbleCache[sectionIndex];
+                    final int currentLevel;
+                    if (currentNibble == null || (currentLevel = currentNibble.getUpdating(localIndex)) >= (propagatedLightLevel - 1)) {
+                        continue; // already at the level we want or unloaded
+                    }
+
+                    final BlockState blockState = this.getBlockState(sectionIndex, localIndex);
+                    if (blockState == null) {
+                        continue;
+                    }
+                    final int opacityCached = blockState.getOpacityIfCached();
+                    if (opacityCached != -1) {
+                        final int targetLevel = propagatedLightLevel - Math.max(1, opacityCached);
+                        if (targetLevel > currentLevel) {
+                            currentNibble.set(localIndex, targetLevel);
+                            this.postLightUpdate(offX, offY, offZ);
+
+                            if (targetLevel > 1) {
+                                if (queueLength >= queue.length) {
+                                    queue = this.resizeIncreaseQueue();
+                                }
+                                queue[queueLength++] =
+                                        ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                                | ((targetLevel & 0xFL) << (6 + 6 + 16))
+                                                | (propagate.everythingButTheOppositeDirection << (6 + 6 + 16 + 4));
+                                continue;
+                            }
+                        }
+                        continue;
+                    } else {
+                        this.mutablePos1.set(offX, offY, offZ);
+                        long flags = 0;
+                        if (blockState.isConditionallyFullOpaque()) {
+                            final VoxelShape cullingFace = blockState.getFaceOcclusionShape(world, this.mutablePos1, propagate.getOpposite().nms);
+
+                            if (Shapes.faceShapeOccludes(Shapes.empty(), cullingFace)) {
+                                continue;
+                            }
+                            flags |= FLAG_HAS_SIDED_TRANSPARENT_BLOCKS;
+                        }
+
+                        final int opacity = blockState.getLightBlock(world, this.mutablePos1);
+                        final int targetLevel = propagatedLightLevel - Math.max(1, opacity);
+                        if (targetLevel <= currentLevel) {
+                            continue;
+                        }
+
+                        currentNibble.set(localIndex, targetLevel);
+                        this.postLightUpdate(offX, offY, offZ);
+
+                        if (targetLevel > 1) {
+                            if (queueLength >= queue.length) {
+                                queue = this.resizeIncreaseQueue();
+                            }
+                            queue[queueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((targetLevel & 0xFL) << (6 + 6 + 16))
+                                            | (propagate.everythingButTheOppositeDirection << (6 + 6 + 16 + 4))
+                                            | (flags);
+                        }
+                        continue;
+                    }
+                }
+            } else {
+                // we actually need to worry about our state here
+                final BlockState fromBlock = this.getBlockState(posX, posY, posZ);
+                this.mutablePos2.set(posX, posY, posZ);
+                for (final AxisDirection propagate : checkDirections) {
+                    final int offX = posX + propagate.x;
+                    final int offY = posY + propagate.y;
+                    final int offZ = posZ + propagate.z;
+
+                    final VoxelShape fromShape = fromBlock.isConditionallyFullOpaque() ? fromBlock.getFaceOcclusionShape(world, this.mutablePos2, propagate.nms) : Shapes.empty();
+
+                    if (fromShape != Shapes.empty() && Shapes.faceShapeOccludes(Shapes.empty(), fromShape)) {
+                        continue;
+                    }
+
+                    final int sectionIndex = (offX >> 4) + 5 * (offZ >> 4) + (5 * 5) * (offY >> 4) + sectionOffset;
+                    final int localIndex = (offX & 15) | ((offZ & 15) << 4) | ((offY & 15) << 8);
+
+                    final SWMRNibbleArray currentNibble = this.nibbleCache[sectionIndex];
+                    final int currentLevel;
+
+                    if (currentNibble == null || (currentLevel = currentNibble.getUpdating(localIndex)) >= (propagatedLightLevel - 1)) {
+                        continue; // already at the level we want
+                    }
+
+                    final BlockState blockState = this.getBlockState(sectionIndex, localIndex);
+                    if (blockState == null) {
+                        continue;
+                    }
+                    final int opacityCached = blockState.getOpacityIfCached();
+                    if (opacityCached != -1) {
+                        final int targetLevel = propagatedLightLevel - Math.max(1, opacityCached);
+                        if (targetLevel > currentLevel) {
+                            currentNibble.set(localIndex, targetLevel);
+                            this.postLightUpdate(offX, offY, offZ);
+
+                            if (targetLevel > 1) {
+                                if (queueLength >= queue.length) {
+                                    queue = this.resizeIncreaseQueue();
+                                }
+                                queue[queueLength++] =
+                                        ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                                | ((targetLevel & 0xFL) << (6 + 6 + 16))
+                                                | (propagate.everythingButTheOppositeDirection << (6 + 6 + 16 + 4));
+                                continue;
+                            }
+                        }
+                        continue;
+                    } else {
+                        this.mutablePos1.set(offX, offY, offZ);
+                        long flags = 0;
+                        if (blockState.isConditionallyFullOpaque()) {
+                            final VoxelShape cullingFace = blockState.getFaceOcclusionShape(world, this.mutablePos1, propagate.getOpposite().nms);
+
+                            if (Shapes.faceShapeOccludes(fromShape, cullingFace)) {
+                                continue;
+                            }
+                            flags |= FLAG_HAS_SIDED_TRANSPARENT_BLOCKS;
+                        }
+
+                        final int opacity = blockState.getLightBlock(world, this.mutablePos1);
+                        final int targetLevel = propagatedLightLevel - Math.max(1, opacity);
+                        if (targetLevel <= currentLevel) {
+                            continue;
+                        }
+
+                        currentNibble.set(localIndex, targetLevel);
+                        this.postLightUpdate(offX, offY, offZ);
+
+                        if (targetLevel > 1) {
+                            if (queueLength >= queue.length) {
+                                queue = this.resizeIncreaseQueue();
+                            }
+                            queue[queueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((targetLevel & 0xFL) << (6 + 6 + 16))
+                                            | (propagate.everythingButTheOppositeDirection << (6 + 6 + 16 + 4))
+                                            | (flags);
+                        }
+                        continue;
+                    }
+                }
+            }
+        }
+    }
+
+    protected final void performLightDecrease(final LightChunkGetter lightAccess) {
+        final BlockGetter world = lightAccess.getLevel();
+        long[] queue = this.decreaseQueue;
+        long[] increaseQueue = this.increaseQueue;
+        int queueReadIndex = 0;
+        int queueLength = this.decreaseQueueInitialLength;
+        this.decreaseQueueInitialLength = 0;
+        int increaseQueueLength = this.increaseQueueInitialLength;
+        final int decodeOffsetX = -this.encodeOffsetX;
+        final int decodeOffsetY = -this.encodeOffsetY;
+        final int decodeOffsetZ = -this.encodeOffsetZ;
+        final int encodeOffset = this.coordinateOffset;
+        final int sectionOffset = this.chunkSectionIndexOffset;
+        final int emittedMask = this.emittedLightMask;
+
+        while (queueReadIndex < queueLength) {
+            final long queueValue = queue[queueReadIndex++];
+
+            final int posX = ((int)queueValue & 63) + decodeOffsetX;
+            final int posZ = (((int)queueValue >>> 6) & 63) + decodeOffsetZ;
+            final int posY = (((int)queueValue >>> 12) & ((1 << 16) - 1)) + decodeOffsetY;
+            final int propagatedLightLevel = (int)((queueValue >>> (6 + 6 + 16)) & 0xF);
+            final AxisDirection[] checkDirections = OLD_CHECK_DIRECTIONS[(int)((queueValue >>> (6 + 6 + 16 + 4)) & 63)];
+
+            if ((queueValue & FLAG_HAS_SIDED_TRANSPARENT_BLOCKS) == 0L) {
+                // we don't need to worry about our state here.
+                for (final AxisDirection propagate : checkDirections) {
+                    final int offX = posX + propagate.x;
+                    final int offY = posY + propagate.y;
+                    final int offZ = posZ + propagate.z;
+
+                    final int sectionIndex = (offX >> 4) + 5 * (offZ >> 4) + (5 * 5) * (offY >> 4) + sectionOffset;
+                    final int localIndex = (offX & 15) | ((offZ & 15) << 4) | ((offY & 15) << 8);
+
+                    final SWMRNibbleArray currentNibble = this.nibbleCache[sectionIndex];
+                    final int lightLevel;
+
+                    if (currentNibble == null || (lightLevel = currentNibble.getUpdating(localIndex)) == 0) {
+                        // already at lowest (or unloaded), nothing we can do
+                        continue;
+                    }
+
+                    final BlockState blockState = this.getBlockState(sectionIndex, localIndex);
+                    if (blockState == null) {
+                        continue;
+                    }
+                    final int opacityCached = blockState.getOpacityIfCached();
+                    if (opacityCached != -1) {
+                        final int targetLevel = Math.max(0, propagatedLightLevel - Math.max(1, opacityCached));
+                        if (lightLevel > targetLevel) {
+                            // it looks like another source propagated here, so re-propagate it
+                            if (increaseQueueLength >= increaseQueue.length) {
+                                increaseQueue = this.resizeIncreaseQueue();
+                            }
+                            increaseQueue[increaseQueueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((lightLevel & 0xFL) << (6 + 6 + 16))
+                                            | (((long)ALL_DIRECTIONS_BITSET) << (6 + 6 + 16 + 4))
+                                            | FLAG_RECHECK_LEVEL;
+                            continue;
+                        }
+                        final int emittedLight = blockState.getLightEmission() & emittedMask;
+                        if (emittedLight != 0) {
+                            // re-propagate source
+                            // note: do not set recheck level, or else the propagation will fail
+                            if (increaseQueueLength >= increaseQueue.length) {
+                                increaseQueue = this.resizeIncreaseQueue();
+                            }
+                            increaseQueue[increaseQueueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((emittedLight & 0xFL) << (6 + 6 + 16))
+                                            | (((long)ALL_DIRECTIONS_BITSET) << (6 + 6 + 16 + 4))
+                                            | (blockState.isConditionallyFullOpaque() ? (FLAG_WRITE_LEVEL | FLAG_HAS_SIDED_TRANSPARENT_BLOCKS) : FLAG_WRITE_LEVEL);
+                        }
+
+                        currentNibble.set(localIndex, 0);
+                        this.postLightUpdate(offX, offY, offZ);
+
+                        if (targetLevel > 0) { // we actually need to propagate 0 just in case we find a neighbour...
+                            if (queueLength >= queue.length) {
+                                queue = this.resizeDecreaseQueue();
+                            }
+                            queue[queueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((targetLevel & 0xFL) << (6 + 6 + 16))
+                                            | ((propagate.everythingButTheOppositeDirection) << (6 + 6 + 16 + 4));
+                            continue;
+                        }
+                        continue;
+                    } else {
+                        this.mutablePos1.set(offX, offY, offZ);
+                        long flags = 0;
+                        if (blockState.isConditionallyFullOpaque()) {
+                            final VoxelShape cullingFace = blockState.getFaceOcclusionShape(world, this.mutablePos1, propagate.getOpposite().nms);
+
+                            if (Shapes.faceShapeOccludes(Shapes.empty(), cullingFace)) {
+                                continue;
+                            }
+                            flags |= FLAG_HAS_SIDED_TRANSPARENT_BLOCKS;
+                        }
+
+                        final int opacity = blockState.getLightBlock(world, this.mutablePos1);
+                        final int targetLevel = Math.max(0, propagatedLightLevel - Math.max(1, opacity));
+                        if (lightLevel > targetLevel) {
+                            // it looks like another source propagated here, so re-propagate it
+                            if (increaseQueueLength >= increaseQueue.length) {
+                                increaseQueue = this.resizeIncreaseQueue();
+                            }
+                            increaseQueue[increaseQueueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((lightLevel & 0xFL) << (6 + 6 + 16))
+                                            | (((long)ALL_DIRECTIONS_BITSET) << (6 + 6 + 16 + 4))
+                                            | (FLAG_RECHECK_LEVEL | flags);
+                            continue;
+                        }
+                        final int emittedLight = blockState.getLightEmission() & emittedMask;
+                        if (emittedLight != 0) {
+                            // re-propagate source
+                            // note: do not set recheck level, or else the propagation will fail
+                            if (increaseQueueLength >= increaseQueue.length) {
+                                increaseQueue = this.resizeIncreaseQueue();
+                            }
+                            increaseQueue[increaseQueueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((emittedLight & 0xFL) << (6 + 6 + 16))
+                                            | (((long)ALL_DIRECTIONS_BITSET) << (6 + 6 + 16 + 4))
+                                            | (flags | FLAG_WRITE_LEVEL);
+                        }
+
+                        currentNibble.set(localIndex, 0);
+                        this.postLightUpdate(offX, offY, offZ);
+
+                        if (targetLevel > 0) {
+                            if (queueLength >= queue.length) {
+                                queue = this.resizeDecreaseQueue();
+                            }
+                            queue[queueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((targetLevel & 0xFL) << (6 + 6 + 16))
+                                            | ((propagate.everythingButTheOppositeDirection) << (6 + 6 + 16 + 4))
+                                            | flags;
+                        }
+                        continue;
+                    }
+                }
+            } else {
+                // we actually need to worry about our state here
+                final BlockState fromBlock = this.getBlockState(posX, posY, posZ);
+                this.mutablePos2.set(posX, posY, posZ);
+                for (final AxisDirection propagate : checkDirections) {
+                    final int offX = posX + propagate.x;
+                    final int offY = posY + propagate.y;
+                    final int offZ = posZ + propagate.z;
+
+                    final int sectionIndex = (offX >> 4) + 5 * (offZ >> 4) + (5 * 5) * (offY >> 4) + sectionOffset;
+                    final int localIndex = (offX & 15) | ((offZ & 15) << 4) | ((offY & 15) << 8);
+
+                    final VoxelShape fromShape = (fromBlock.isConditionallyFullOpaque()) ? fromBlock.getFaceOcclusionShape(world, this.mutablePos2, propagate.nms) : Shapes.empty();
+
+                    if (fromShape != Shapes.empty() && Shapes.faceShapeOccludes(Shapes.empty(), fromShape)) {
+                        continue;
+                    }
+
+                    final SWMRNibbleArray currentNibble = this.nibbleCache[sectionIndex];
+                    final int lightLevel;
+
+                    if (currentNibble == null || (lightLevel = currentNibble.getUpdating(localIndex)) == 0) {
+                        // already at lowest (or unloaded), nothing we can do
+                        continue;
+                    }
+
+                    final BlockState blockState = this.getBlockState(sectionIndex, localIndex);
+                    if (blockState == null) {
+                        continue;
+                    }
+                    final int opacityCached = blockState.getOpacityIfCached();
+                    if (opacityCached != -1) {
+                        final int targetLevel = Math.max(0, propagatedLightLevel - Math.max(1, opacityCached));
+                        if (lightLevel > targetLevel) {
+                            // it looks like another source propagated here, so re-propagate it
+                            if (increaseQueueLength >= increaseQueue.length) {
+                                increaseQueue = this.resizeIncreaseQueue();
+                            }
+                            increaseQueue[increaseQueueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((lightLevel & 0xFL) << (6 + 6 + 16))
+                                            | (((long)ALL_DIRECTIONS_BITSET) << (6 + 6 + 16 + 4))
+                                            | FLAG_RECHECK_LEVEL;
+                            continue;
+                        }
+                        final int emittedLight = blockState.getLightEmission() & emittedMask;
+                        if (emittedLight != 0) {
+                            // re-propagate source
+                            // note: do not set recheck level, or else the propagation will fail
+                            if (increaseQueueLength >= increaseQueue.length) {
+                                increaseQueue = this.resizeIncreaseQueue();
+                            }
+                            increaseQueue[increaseQueueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((emittedLight & 0xFL) << (6 + 6 + 16))
+                                            | (((long)ALL_DIRECTIONS_BITSET) << (6 + 6 + 16 + 4))
+                                            | (blockState.isConditionallyFullOpaque() ? (FLAG_WRITE_LEVEL | FLAG_HAS_SIDED_TRANSPARENT_BLOCKS) : FLAG_WRITE_LEVEL);
+                        }
+
+                        currentNibble.set(localIndex, 0);
+                        this.postLightUpdate(offX, offY, offZ);
+
+                        if (targetLevel > 0) { // we actually need to propagate 0 just in case we find a neighbour...
+                            if (queueLength >= queue.length) {
+                                queue = this.resizeDecreaseQueue();
+                            }
+                            queue[queueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((targetLevel & 0xFL) << (6 + 6 + 16))
+                                            | ((propagate.everythingButTheOppositeDirection) << (6 + 6 + 16 + 4));
+                            continue;
+                        }
+                        continue;
+                    } else {
+                        this.mutablePos1.set(offX, offY, offZ);
+                        long flags = 0;
+                        if (blockState.isConditionallyFullOpaque()) {
+                            final VoxelShape cullingFace = blockState.getFaceOcclusionShape(world, this.mutablePos1, propagate.getOpposite().nms);
+
+                            if (Shapes.faceShapeOccludes(fromShape, cullingFace)) {
+                                continue;
+                            }
+                            flags |= FLAG_HAS_SIDED_TRANSPARENT_BLOCKS;
+                        }
+
+                        final int opacity = blockState.getLightBlock(world, this.mutablePos1);
+                        final int targetLevel = Math.max(0, propagatedLightLevel - Math.max(1, opacity));
+                        if (lightLevel > targetLevel) {
+                            // it looks like another source propagated here, so re-propagate it
+                            if (increaseQueueLength >= increaseQueue.length) {
+                                increaseQueue = this.resizeIncreaseQueue();
+                            }
+                            increaseQueue[increaseQueueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((lightLevel & 0xFL) << (6 + 6 + 16))
+                                            | (((long)ALL_DIRECTIONS_BITSET) << (6 + 6 + 16 + 4))
+                                            | (FLAG_RECHECK_LEVEL | flags);
+                            continue;
+                        }
+                        final int emittedLight = blockState.getLightEmission() & emittedMask;
+                        if (emittedLight != 0) {
+                            // re-propagate source
+                            // note: do not set recheck level, or else the propagation will fail
+                            if (increaseQueueLength >= increaseQueue.length) {
+                                increaseQueue = this.resizeIncreaseQueue();
+                            }
+                            increaseQueue[increaseQueueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((emittedLight & 0xFL) << (6 + 6 + 16))
+                                            | (((long)ALL_DIRECTIONS_BITSET) << (6 + 6 + 16 + 4))
+                                            | (flags | FLAG_WRITE_LEVEL);
+                        }
+
+                        currentNibble.set(localIndex, 0);
+                        this.postLightUpdate(offX, offY, offZ);
+
+                        if (targetLevel > 0) { // we actually need to propagate 0 just in case we find a neighbour...
+                            if (queueLength >= queue.length) {
+                                queue = this.resizeDecreaseQueue();
+                            }
+                            queue[queueLength++] =
+                                    ((offX + (offZ << 6) + (offY << 12) + encodeOffset) & ((1L << (6 + 6 + 16)) - 1))
+                                            | ((targetLevel & 0xFL) << (6 + 6 + 16))
+                                            | ((propagate.everythingButTheOppositeDirection) << (6 + 6 + 16 + 4))
+                                            | flags;
+                        }
+                        continue;
+                    }
+                }
+            }
+        }
+
+        // propagate sources we clobbered
+        this.increaseQueueInitialLength = increaseQueueLength;
+        this.performLightIncrease(lightAccess);
+    }
+}
diff --git a/src/main/java/ca/spottedleaf/starlight/common/light/StarLightInterface.java b/src/main/java/ca/spottedleaf/starlight/common/light/StarLightInterface.java
new file mode 100644
index 0000000000000000000000000000000000000000..146c78a333e47cb4d8aa97700e19a12ca176ce76
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/starlight/common/light/StarLightInterface.java
@@ -0,0 +1,673 @@
+package ca.spottedleaf.starlight.common.light;
+
+import ca.spottedleaf.starlight.common.util.CoordinateUtils;
+import ca.spottedleaf.starlight.common.util.WorldUtil;
+import it.unimi.dsi.fastutil.longs.Long2ObjectLinkedOpenHashMap;
+import it.unimi.dsi.fastutil.shorts.ShortCollection;
+import it.unimi.dsi.fastutil.shorts.ShortOpenHashSet;
+import it.unimi.dsi.fastutil.objects.ObjectOpenHashSet;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.SectionPos;
+import net.minecraft.server.level.ServerChunkCache;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.TicketType;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkStatus;
+import net.minecraft.world.level.chunk.DataLayer;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.chunk.LightChunkGetter;
+import net.minecraft.world.level.lighting.LayerLightEventListener;
+import net.minecraft.world.level.lighting.LevelLightEngine;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import java.util.function.Consumer;
+import java.util.function.IntConsumer;
+
+public final class StarLightInterface {
+
+    public static final TicketType<ChunkPos> CHUNK_WORK_TICKET = TicketType.create("starlight_chunk_work_ticket", (p1, p2) -> Long.compare(p1.toLong(), p2.toLong()));
+
+    /**
+     * Can be {@code null}, indicating the light is all empty.
+     */
+    protected final Level world;
+    protected final LightChunkGetter lightAccess;
+
+    protected final ArrayDeque<SkyStarLightEngine> cachedSkyPropagators;
+    protected final ArrayDeque<BlockStarLightEngine> cachedBlockPropagators;
+
+    protected final LightQueue lightQueue = new LightQueue(this);
+
+    protected final LayerLightEventListener skyReader;
+    protected final LayerLightEventListener blockReader;
+    protected final boolean isClientSide;
+
+    protected final int minSection;
+    protected final int maxSection;
+    protected final int minLightSection;
+    protected final int maxLightSection;
+
+    public final LevelLightEngine lightEngine;
+
+    private final boolean hasBlockLight;
+    private final boolean hasSkyLight;
+
+    public StarLightInterface(final LightChunkGetter lightAccess, final boolean hasSkyLight, final boolean hasBlockLight, final LevelLightEngine lightEngine) {
+        this.lightAccess = lightAccess;
+        this.world = lightAccess == null ? null : (Level)lightAccess.getLevel();
+        this.cachedSkyPropagators = hasSkyLight && lightAccess != null ? new ArrayDeque<>() : null;
+        this.cachedBlockPropagators = hasBlockLight && lightAccess != null ? new ArrayDeque<>() : null;
+        this.isClientSide = !(this.world instanceof ServerLevel);
+        if (this.world == null) {
+            this.minSection = -4;
+            this.maxSection = 19;
+            this.minLightSection = -5;
+            this.maxLightSection = 20;
+        } else {
+            this.minSection = WorldUtil.getMinSection(this.world);
+            this.maxSection = WorldUtil.getMaxSection(this.world);
+            this.minLightSection = WorldUtil.getMinLightSection(this.world);
+            this.maxLightSection = WorldUtil.getMaxLightSection(this.world);
+        }
+        this.lightEngine = lightEngine;
+        this.hasBlockLight = hasBlockLight;
+        this.hasSkyLight = hasSkyLight;
+        this.skyReader = !hasSkyLight ? LayerLightEventListener.DummyLightLayerEventListener.INSTANCE : new LayerLightEventListener() {
+            @Override
+            public void checkBlock(final BlockPos blockPos) {
+                StarLightInterface.this.lightEngine.checkBlock(blockPos.immutable());
+            }
+
+            @Override
+            public void propagateLightSources(final ChunkPos chunkPos) {
+                throw new UnsupportedOperationException();
+            }
+
+            @Override
+            public boolean hasLightWork() {
+                // not really correct...
+                return StarLightInterface.this.hasUpdates();
+            }
+
+            @Override
+            public int runLightUpdates() {
+                throw new UnsupportedOperationException();
+            }
+
+            @Override
+            public void setLightEnabled(final ChunkPos chunkPos, final boolean bl) {
+                throw new UnsupportedOperationException();
+            }
+
+            @Override
+            public DataLayer getDataLayerData(final SectionPos pos) {
+                final ChunkAccess chunk = StarLightInterface.this.getAnyChunkNow(pos.getX(), pos.getZ());
+                if (chunk == null || (!StarLightInterface.this.isClientSide && !chunk.isLightCorrect()) || !chunk.getStatus().isOrAfter(ChunkStatus.LIGHT)) {
+                    return null;
+                }
+
+                final int sectionY = pos.getY();
+
+                if (sectionY > StarLightInterface.this.maxLightSection || sectionY < StarLightInterface.this.minLightSection) {
+                    return null;
+                }
+
+                if (chunk.getSkyEmptinessMap() == null) {
+                    return null;
+                }
+
+                return chunk.getSkyNibbles()[sectionY - StarLightInterface.this.minLightSection].toVanillaNibble();
+            }
+
+            @Override
+            public int getLightValue(final BlockPos blockPos) {
+                return StarLightInterface.this.getSkyLightValue(blockPos, StarLightInterface.this.getAnyChunkNow(blockPos.getX() >> 4, blockPos.getZ() >> 4));
+            }
+
+            @Override
+            public void updateSectionStatus(final SectionPos pos, final boolean notReady) {
+                StarLightInterface.this.sectionChange(pos, notReady);
+            }
+        };
+        this.blockReader = !hasBlockLight ? LayerLightEventListener.DummyLightLayerEventListener.INSTANCE : new LayerLightEventListener() {
+            @Override
+            public void checkBlock(final BlockPos blockPos) {
+                StarLightInterface.this.lightEngine.checkBlock(blockPos.immutable());
+            }
+
+            @Override
+            public void propagateLightSources(final ChunkPos chunkPos) {
+                throw new UnsupportedOperationException();
+            }
+
+            @Override
+            public boolean hasLightWork() {
+                // not really correct...
+                return StarLightInterface.this.hasUpdates();
+            }
+
+            @Override
+            public int runLightUpdates() {
+                throw new UnsupportedOperationException();
+            }
+
+            @Override
+            public void setLightEnabled(final ChunkPos chunkPos, final boolean bl) {
+                throw new UnsupportedOperationException();
+            }
+
+            @Override
+            public DataLayer getDataLayerData(final SectionPos pos) {
+                final ChunkAccess chunk = StarLightInterface.this.getAnyChunkNow(pos.getX(), pos.getZ());
+
+                if (chunk == null || pos.getY() < StarLightInterface.this.minLightSection || pos.getY() > StarLightInterface.this.maxLightSection) {
+                    return null;
+                }
+
+                return chunk.getBlockNibbles()[pos.getY() - StarLightInterface.this.minLightSection].toVanillaNibble();
+            }
+
+            @Override
+            public int getLightValue(final BlockPos blockPos) {
+                return StarLightInterface.this.getBlockLightValue(blockPos, StarLightInterface.this.getAnyChunkNow(blockPos.getX() >> 4, blockPos.getZ() >> 4));
+            }
+
+            @Override
+            public void updateSectionStatus(final SectionPos pos, final boolean notReady) {
+                StarLightInterface.this.sectionChange(pos, notReady);
+            }
+        };
+    }
+
+    public boolean hasSkyLight() {
+        return this.hasSkyLight;
+    }
+
+    public boolean hasBlockLight() {
+        return this.hasBlockLight;
+    }
+
+    protected int getSkyLightValue(final BlockPos blockPos, final ChunkAccess chunk) {
+        if (!this.hasSkyLight) {
+            return 0;
+        }
+        final int x = blockPos.getX();
+        int y = blockPos.getY();
+        final int z = blockPos.getZ();
+
+        final int minSection = this.minSection;
+        final int maxSection = this.maxSection;
+        final int minLightSection = this.minLightSection;
+        final int maxLightSection = this.maxLightSection;
+
+        if (chunk == null || (!this.isClientSide && !chunk.isLightCorrect()) || !chunk.getStatus().isOrAfter(ChunkStatus.LIGHT)) {
+            return 15;
+        }
+
+        int sectionY = y >> 4;
+
+        if (sectionY > maxLightSection) {
+            return 15;
+        }
+
+        if (sectionY < minLightSection) {
+            sectionY = minLightSection;
+            y = sectionY << 4;
+        }
+
+        final SWMRNibbleArray[] nibbles = chunk.getSkyNibbles();
+        final SWMRNibbleArray immediate = nibbles[sectionY - minLightSection];
+
+        if (!immediate.isNullNibbleVisible()) {
+            return immediate.getVisible(x, y, z);
+        }
+
+        final boolean[] emptinessMap = chunk.getSkyEmptinessMap();
+
+        if (emptinessMap == null) {
+            return 15;
+        }
+
+        // are we above this chunk's lowest empty section?
+        int lowestY = minLightSection - 1;
+        for (int currY = maxSection; currY >= minSection; --currY) {
+            if (emptinessMap[currY - minSection]) {
+                continue;
+            }
+
+            // should always be full lit here
+            lowestY = currY;
+            break;
+        }
+
+        if (sectionY > lowestY) {
+            return 15;
+        }
+
+        // this nibble is going to depend solely on the skylight data above it
+        // find first non-null data above (there does exist one, as we just found it above)
+        for (int currY = sectionY + 1; currY <= maxLightSection; ++currY) {
+            final SWMRNibbleArray nibble = nibbles[currY - minLightSection];
+            if (!nibble.isNullNibbleVisible()) {
+                return nibble.getVisible(x, 0, z);
+            }
+        }
+
+        // should never reach here
+        return 15;
+    }
+
+    protected int getBlockLightValue(final BlockPos blockPos, final ChunkAccess chunk) {
+        if (!this.hasBlockLight) {
+            return 0;
+        }
+        final int y = blockPos.getY();
+        final int cy = y >> 4;
+
+        final int minLightSection = this.minLightSection;
+        final int maxLightSection = this.maxLightSection;
+
+        if (cy < minLightSection || cy > maxLightSection) {
+            return 0;
+        }
+
+        if (chunk == null) {
+            return 0;
+        }
+
+        final SWMRNibbleArray nibble = chunk.getBlockNibbles()[cy - minLightSection];
+        return nibble.getVisible(blockPos.getX(), y, blockPos.getZ());
+    }
+
+    public int getRawBrightness(final BlockPos pos, final int ambientDarkness) {
+        final ChunkAccess chunk = this.getAnyChunkNow(pos.getX() >> 4, pos.getZ() >> 4);
+
+        final int sky = this.getSkyLightValue(pos, chunk) - ambientDarkness;
+        // Don't fetch the block light level if the skylight level is 15, since the value will never be higher.
+        if (sky == 15) return 15;
+        final int block = this.getBlockLightValue(pos, chunk);
+        return Math.max(sky, block);
+    }
+
+    public LayerLightEventListener getSkyReader() {
+        return this.skyReader;
+    }
+
+    public LayerLightEventListener getBlockReader() {
+        return this.blockReader;
+    }
+
+    public boolean isClientSide() {
+        return this.isClientSide;
+    }
+
+    public ChunkAccess getAnyChunkNow(final int chunkX, final int chunkZ) {
+        if (this.world == null) {
+            // empty world
+            return null;
+        }
+
+        final ServerChunkCache chunkProvider =  ((ServerLevel)this.world).getChunkSource();
+        final LevelChunk fullLoaded = chunkProvider.getChunkAtIfLoadedImmediately(chunkX, chunkZ);
+        if (fullLoaded != null) {
+            return fullLoaded;
+        }
+
+        return chunkProvider.getChunkAtImmediately(chunkX, chunkZ);
+    }
+
+    public boolean hasUpdates() {
+        return !this.lightQueue.isEmpty();
+    }
+
+    public Level getWorld() {
+        return this.world;
+    }
+
+    public LightChunkGetter getLightAccess() {
+        return this.lightAccess;
+    }
+
+    protected final SkyStarLightEngine getSkyLightEngine() {
+        if (this.cachedSkyPropagators == null) {
+            return null;
+        }
+        final SkyStarLightEngine ret;
+        synchronized (this.cachedSkyPropagators) {
+            ret = this.cachedSkyPropagators.pollFirst();
+        }
+
+        if (ret == null) {
+            return new SkyStarLightEngine(this.world);
+        }
+        return ret;
+    }
+
+    protected final void releaseSkyLightEngine(final SkyStarLightEngine engine) {
+        if (this.cachedSkyPropagators == null) {
+            return;
+        }
+        synchronized (this.cachedSkyPropagators) {
+            this.cachedSkyPropagators.addFirst(engine);
+        }
+    }
+
+    protected final BlockStarLightEngine getBlockLightEngine() {
+        if (this.cachedBlockPropagators == null) {
+            return null;
+        }
+        final BlockStarLightEngine ret;
+        synchronized (this.cachedBlockPropagators) {
+            ret = this.cachedBlockPropagators.pollFirst();
+        }
+
+        if (ret == null) {
+            return new BlockStarLightEngine(this.world);
+        }
+        return ret;
+    }
+
+    protected final void releaseBlockLightEngine(final BlockStarLightEngine engine) {
+        if (this.cachedBlockPropagators == null) {
+            return;
+        }
+        synchronized (this.cachedBlockPropagators) {
+            this.cachedBlockPropagators.addFirst(engine);
+        }
+    }
+
+    public CompletableFuture<Void> blockChange(final BlockPos pos) {
+        if (this.world == null || pos.getY() < WorldUtil.getMinBlockY(this.world) || pos.getY() > WorldUtil.getMaxBlockY(this.world)) { // empty world
+            return null;
+        }
+
+        return this.lightQueue.queueBlockChange(pos);
+    }
+
+    public CompletableFuture<Void> sectionChange(final SectionPos pos, final boolean newEmptyValue) {
+        if (this.world == null) { // empty world
+            return null;
+        }
+
+        return this.lightQueue.queueSectionChange(pos, newEmptyValue);
+    }
+
+    public void forceLoadInChunk(final ChunkAccess chunk, final Boolean[] emptySections) {
+        final SkyStarLightEngine skyEngine = this.getSkyLightEngine();
+        final BlockStarLightEngine blockEngine = this.getBlockLightEngine();
+
+        try {
+            if (skyEngine != null) {
+                skyEngine.forceHandleEmptySectionChanges(this.lightAccess, chunk, emptySections);
+            }
+            if (blockEngine != null) {
+                blockEngine.forceHandleEmptySectionChanges(this.lightAccess, chunk, emptySections);
+            }
+        } finally {
+            this.releaseSkyLightEngine(skyEngine);
+            this.releaseBlockLightEngine(blockEngine);
+        }
+    }
+
+    public void loadInChunk(final int chunkX, final int chunkZ, final Boolean[] emptySections) {
+        final SkyStarLightEngine skyEngine = this.getSkyLightEngine();
+        final BlockStarLightEngine blockEngine = this.getBlockLightEngine();
+
+        try {
+            if (skyEngine != null) {
+                skyEngine.handleEmptySectionChanges(this.lightAccess, chunkX, chunkZ, emptySections);
+            }
+            if (blockEngine != null) {
+                blockEngine.handleEmptySectionChanges(this.lightAccess, chunkX, chunkZ, emptySections);
+            }
+        } finally {
+            this.releaseSkyLightEngine(skyEngine);
+            this.releaseBlockLightEngine(blockEngine);
+        }
+    }
+
+    public void lightChunk(final ChunkAccess chunk, final Boolean[] emptySections) {
+        final SkyStarLightEngine skyEngine = this.getSkyLightEngine();
+        final BlockStarLightEngine blockEngine = this.getBlockLightEngine();
+
+        try {
+            if (skyEngine != null) {
+                skyEngine.light(this.lightAccess, chunk, emptySections);
+            }
+            if (blockEngine != null) {
+                blockEngine.light(this.lightAccess, chunk, emptySections);
+            }
+        } finally {
+            this.releaseSkyLightEngine(skyEngine);
+            this.releaseBlockLightEngine(blockEngine);
+        }
+    }
+
+    public void relightChunks(final Set<ChunkPos> chunks, final Consumer<ChunkPos> chunkLightCallback,
+                              final IntConsumer onComplete) {
+        final SkyStarLightEngine skyEngine = this.getSkyLightEngine();
+        final BlockStarLightEngine blockEngine = this.getBlockLightEngine();
+
+        try {
+            if (skyEngine != null) {
+                skyEngine.relightChunks(this.lightAccess, chunks, blockEngine == null ? chunkLightCallback : null,
+                        blockEngine == null ? onComplete : null);
+            }
+            if (blockEngine != null) {
+                blockEngine.relightChunks(this.lightAccess, chunks, chunkLightCallback, onComplete);
+            }
+        } finally {
+            this.releaseSkyLightEngine(skyEngine);
+            this.releaseBlockLightEngine(blockEngine);
+        }
+    }
+
+    public void checkChunkEdges(final int chunkX, final int chunkZ) {
+        this.checkSkyEdges(chunkX, chunkZ);
+        this.checkBlockEdges(chunkX, chunkZ);
+    }
+
+    public void checkSkyEdges(final int chunkX, final int chunkZ) {
+        final SkyStarLightEngine skyEngine = this.getSkyLightEngine();
+
+        try {
+            if (skyEngine != null) {
+                skyEngine.checkChunkEdges(this.lightAccess, chunkX, chunkZ);
+            }
+        } finally {
+            this.releaseSkyLightEngine(skyEngine);
+        }
+    }
+
+    public void checkBlockEdges(final int chunkX, final int chunkZ) {
+        final BlockStarLightEngine blockEngine = this.getBlockLightEngine();
+        try {
+            if (blockEngine != null) {
+                blockEngine.checkChunkEdges(this.lightAccess, chunkX, chunkZ);
+            }
+        } finally {
+            this.releaseBlockLightEngine(blockEngine);
+        }
+    }
+
+    public void checkSkyEdges(final int chunkX, final int chunkZ, final ShortCollection sections) {
+        final SkyStarLightEngine skyEngine = this.getSkyLightEngine();
+
+        try {
+            if (skyEngine != null) {
+                skyEngine.checkChunkEdges(this.lightAccess, chunkX, chunkZ, sections);
+            }
+        } finally {
+            this.releaseSkyLightEngine(skyEngine);
+        }
+    }
+
+    public void checkBlockEdges(final int chunkX, final int chunkZ, final ShortCollection sections) {
+        final BlockStarLightEngine blockEngine = this.getBlockLightEngine();
+        try {
+            if (blockEngine != null) {
+                blockEngine.checkChunkEdges(this.lightAccess, chunkX, chunkZ, sections);
+            }
+        } finally {
+            this.releaseBlockLightEngine(blockEngine);
+        }
+    }
+
+    public void scheduleChunkLight(final ChunkPos pos, final Runnable run) {
+        this.lightQueue.queueChunkLighting(pos, run);
+    }
+
+    public void removeChunkTasks(final ChunkPos pos) {
+        this.lightQueue.removeChunk(pos);
+    }
+
+    public void propagateChanges() {
+        if (this.lightQueue.isEmpty()) {
+            return;
+        }
+
+        final SkyStarLightEngine skyEngine = this.getSkyLightEngine();
+        final BlockStarLightEngine blockEngine = this.getBlockLightEngine();
+
+        try {
+            LightQueue.ChunkTasks task;
+            while ((task = this.lightQueue.removeFirstTask()) != null) {
+                if (task.lightTasks != null) {
+                    for (final Runnable run : task.lightTasks) {
+                        run.run();
+                    }
+                }
+
+                final long coordinate = task.chunkCoordinate;
+                final int chunkX = CoordinateUtils.getChunkX(coordinate);
+                final int chunkZ = CoordinateUtils.getChunkZ(coordinate);
+
+                final Set<BlockPos> positions = task.changedPositions;
+                final Boolean[] sectionChanges = task.changedSectionSet;
+
+                if (skyEngine != null && (!positions.isEmpty() || sectionChanges != null)) {
+                    skyEngine.blocksChangedInChunk(this.lightAccess, chunkX, chunkZ, positions, sectionChanges);
+                }
+                if (blockEngine != null && (!positions.isEmpty() || sectionChanges != null)) {
+                    blockEngine.blocksChangedInChunk(this.lightAccess, chunkX, chunkZ, positions, sectionChanges);
+                }
+
+                if (skyEngine != null && task.queuedEdgeChecksSky != null) {
+                    skyEngine.checkChunkEdges(this.lightAccess, chunkX, chunkZ, task.queuedEdgeChecksSky);
+                }
+                if (blockEngine != null && task.queuedEdgeChecksBlock != null) {
+                    blockEngine.checkChunkEdges(this.lightAccess, chunkX, chunkZ, task.queuedEdgeChecksBlock);
+                }
+
+                task.onComplete.complete(null);
+            }
+        } finally {
+            this.releaseSkyLightEngine(skyEngine);
+            this.releaseBlockLightEngine(blockEngine);
+        }
+    }
+
+    protected static final class LightQueue {
+
+        protected final Long2ObjectLinkedOpenHashMap<ChunkTasks> chunkTasks = new Long2ObjectLinkedOpenHashMap<>();
+        protected final StarLightInterface manager;
+
+        public LightQueue(final StarLightInterface manager) {
+            this.manager = manager;
+        }
+
+        public synchronized boolean isEmpty() {
+            return this.chunkTasks.isEmpty();
+        }
+
+        public synchronized CompletableFuture<Void> queueBlockChange(final BlockPos pos) {
+            final ChunkTasks tasks = this.chunkTasks.computeIfAbsent(CoordinateUtils.getChunkKey(pos), ChunkTasks::new);
+            tasks.changedPositions.add(pos.immutable());
+            return tasks.onComplete;
+        }
+
+        public synchronized CompletableFuture<Void> queueSectionChange(final SectionPos pos, final boolean newEmptyValue) {
+            final ChunkTasks tasks = this.chunkTasks.computeIfAbsent(CoordinateUtils.getChunkKey(pos), ChunkTasks::new);
+
+            if (tasks.changedSectionSet == null) {
+                tasks.changedSectionSet = new Boolean[this.manager.maxSection - this.manager.minSection + 1];
+            }
+            tasks.changedSectionSet[pos.getY() - this.manager.minSection] = Boolean.valueOf(newEmptyValue);
+
+            return tasks.onComplete;
+        }
+
+        public synchronized CompletableFuture<Void> queueChunkLighting(final ChunkPos pos, final Runnable lightTask) {
+            final ChunkTasks tasks = this.chunkTasks.computeIfAbsent(CoordinateUtils.getChunkKey(pos), ChunkTasks::new);
+            if (tasks.lightTasks == null) {
+                tasks.lightTasks = new ArrayList<>();
+            }
+            tasks.lightTasks.add(lightTask);
+
+            return tasks.onComplete;
+        }
+
+        public synchronized CompletableFuture<Void> queueChunkSkylightEdgeCheck(final SectionPos pos, final ShortCollection sections) {
+            final ChunkTasks tasks = this.chunkTasks.computeIfAbsent(CoordinateUtils.getChunkKey(pos), ChunkTasks::new);
+
+            ShortOpenHashSet queuedEdges = tasks.queuedEdgeChecksSky;
+            if (queuedEdges == null) {
+                queuedEdges = tasks.queuedEdgeChecksSky = new ShortOpenHashSet();
+            }
+            queuedEdges.addAll(sections);
+
+            return tasks.onComplete;
+        }
+
+        public synchronized CompletableFuture<Void> queueChunkBlocklightEdgeCheck(final SectionPos pos, final ShortCollection sections) {
+            final ChunkTasks tasks = this.chunkTasks.computeIfAbsent(CoordinateUtils.getChunkKey(pos), ChunkTasks::new);
+
+            ShortOpenHashSet queuedEdges = tasks.queuedEdgeChecksBlock;
+            if (queuedEdges == null) {
+                queuedEdges = tasks.queuedEdgeChecksBlock = new ShortOpenHashSet();
+            }
+            queuedEdges.addAll(sections);
+
+            return tasks.onComplete;
+        }
+
+        public void removeChunk(final ChunkPos pos) {
+            final ChunkTasks tasks;
+            synchronized (this) {
+                tasks = this.chunkTasks.remove(CoordinateUtils.getChunkKey(pos));
+            }
+            if (tasks != null) {
+                tasks.onComplete.complete(null);
+            }
+        }
+
+        public synchronized ChunkTasks removeFirstTask() {
+            if (this.chunkTasks.isEmpty()) {
+                return null;
+            }
+            return this.chunkTasks.removeFirst();
+        }
+
+        protected static final class ChunkTasks {
+
+            public final Set<BlockPos> changedPositions = new ObjectOpenHashSet<>();
+            public Boolean[] changedSectionSet;
+            public ShortOpenHashSet queuedEdgeChecksSky;
+            public ShortOpenHashSet queuedEdgeChecksBlock;
+            public List<Runnable> lightTasks;
+
+            public final CompletableFuture<Void> onComplete = new CompletableFuture<>();
+
+            public final long chunkCoordinate;
+
+            public ChunkTasks(final long chunkCoordinate) {
+                this.chunkCoordinate = chunkCoordinate;
+            }
+        }
+    }
+}
diff --git a/src/main/java/ca/spottedleaf/starlight/common/util/CoordinateUtils.java b/src/main/java/ca/spottedleaf/starlight/common/util/CoordinateUtils.java
new file mode 100644
index 0000000000000000000000000000000000000000..16a4a14e7ccf9e4d7fdf1166674fe8f529c06d39
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/starlight/common/util/CoordinateUtils.java
@@ -0,0 +1,128 @@
+package ca.spottedleaf.starlight.common.util;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.SectionPos;
+import net.minecraft.util.Mth;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.level.ChunkPos;
+
+public final class CoordinateUtils {
+
+    // dx, dz are relative to the target chunk
+    // dx, dz in [-radius, radius]
+    public static int getNeighbourMappedIndex(final int dx, final int dz, final int radius) {
+        return (dx + radius) + (2 * radius + 1)*(dz + radius);
+    }
+
+    // the chunk keys are compatible with vanilla
+
+    public static long getChunkKey(final BlockPos pos) {
+        return ((long)(pos.getZ() >> 4) << 32) | ((pos.getX() >> 4) & 0xFFFFFFFFL);
+    }
+
+    public static long getChunkKey(final Entity entity) {
+        return ((long)(Mth.floor(entity.getZ()) >> 4) << 32) | ((Mth.floor(entity.getX()) >> 4) & 0xFFFFFFFFL);
+    }
+
+    public static long getChunkKey(final ChunkPos pos) {
+        return ((long)pos.z << 32) | (pos.x & 0xFFFFFFFFL);
+    }
+
+    public static long getChunkKey(final SectionPos pos) {
+        return ((long)pos.getZ() << 32) | (pos.getX() & 0xFFFFFFFFL);
+    }
+
+    public static long getChunkKey(final int x, final int z) {
+        return ((long)z << 32) | (x & 0xFFFFFFFFL);
+    }
+
+    public static int getChunkX(final long chunkKey) {
+        return (int)chunkKey;
+    }
+
+    public static int getChunkZ(final long chunkKey) {
+        return (int)(chunkKey >>> 32);
+    }
+
+    public static int getChunkCoordinate(final double blockCoordinate) {
+        return Mth.floor(blockCoordinate) >> 4;
+    }
+
+    // the section keys are compatible with vanilla's
+
+    static final int SECTION_X_BITS = 22;
+    static final long SECTION_X_MASK = (1L << SECTION_X_BITS) - 1;
+    static final int SECTION_Y_BITS = 20;
+    static final long SECTION_Y_MASK = (1L << SECTION_Y_BITS) - 1;
+    static final int SECTION_Z_BITS = 22;
+    static final long SECTION_Z_MASK = (1L << SECTION_Z_BITS) - 1;
+    // format is y,z,x (in order of LSB to MSB)
+    static final int SECTION_Y_SHIFT = 0;
+    static final int SECTION_Z_SHIFT = SECTION_Y_SHIFT + SECTION_Y_BITS;
+    static final int SECTION_X_SHIFT = SECTION_Z_SHIFT + SECTION_X_BITS;
+    static final int SECTION_TO_BLOCK_SHIFT = 4;
+
+    public static long getChunkSectionKey(final int x, final int y, final int z) {
+        return ((x & SECTION_X_MASK) << SECTION_X_SHIFT)
+                | ((y & SECTION_Y_MASK) << SECTION_Y_SHIFT)
+                | ((z & SECTION_Z_MASK) << SECTION_Z_SHIFT);
+    }
+
+    public static long getChunkSectionKey(final SectionPos pos) {
+        return ((pos.getX() & SECTION_X_MASK) << SECTION_X_SHIFT)
+                | ((pos.getY() & SECTION_Y_MASK) << SECTION_Y_SHIFT)
+                | ((pos.getZ() & SECTION_Z_MASK) << SECTION_Z_SHIFT);
+    }
+
+    public static long getChunkSectionKey(final ChunkPos pos, final int y) {
+        return ((pos.x & SECTION_X_MASK) << SECTION_X_SHIFT)
+                | ((y & SECTION_Y_MASK) << SECTION_Y_SHIFT)
+                | ((pos.z & SECTION_Z_MASK) << SECTION_Z_SHIFT);
+    }
+
+    public static long getChunkSectionKey(final BlockPos pos) {
+        return (((long)pos.getX() << (SECTION_X_SHIFT - SECTION_TO_BLOCK_SHIFT)) & (SECTION_X_MASK << SECTION_X_SHIFT)) |
+                ((pos.getY() >> SECTION_TO_BLOCK_SHIFT) & (SECTION_Y_MASK << SECTION_Y_SHIFT)) |
+                (((long)pos.getZ() << (SECTION_Z_SHIFT - SECTION_TO_BLOCK_SHIFT)) & (SECTION_Z_MASK << SECTION_Z_SHIFT));
+    }
+
+    public static long getChunkSectionKey(final Entity entity) {
+        return ((Mth.lfloor(entity.getX()) << (SECTION_X_SHIFT - SECTION_TO_BLOCK_SHIFT)) & (SECTION_X_MASK << SECTION_X_SHIFT)) |
+                ((Mth.lfloor(entity.getY()) >> SECTION_TO_BLOCK_SHIFT) & (SECTION_Y_MASK << SECTION_Y_SHIFT)) |
+                ((Mth.lfloor(entity.getZ()) << (SECTION_Z_SHIFT - SECTION_TO_BLOCK_SHIFT)) & (SECTION_Z_MASK << SECTION_Z_SHIFT));
+    }
+
+    public static int getChunkSectionX(final long key) {
+        return (int)(key << (Long.SIZE - (SECTION_X_SHIFT + SECTION_X_BITS)) >> (Long.SIZE - SECTION_X_BITS));
+    }
+
+    public static int getChunkSectionY(final long key) {
+        return (int)(key << (Long.SIZE - (SECTION_Y_SHIFT + SECTION_Y_BITS)) >> (Long.SIZE - SECTION_Y_BITS));
+    }
+
+    public static int getChunkSectionZ(final long key) {
+        return (int)(key << (Long.SIZE - (SECTION_Z_SHIFT + SECTION_Z_BITS)) >> (Long.SIZE - SECTION_Z_BITS));
+    }
+
+    // the block coordinates are not necessarily compatible with vanilla's
+
+    public static int getBlockCoordinate(final double blockCoordinate) {
+        return Mth.floor(blockCoordinate);
+    }
+
+    public static long getBlockKey(final int x, final int y, final int z) {
+        return ((long)x & 0x7FFFFFF) | (((long)z & 0x7FFFFFF) << 27) | ((long)y << 54);
+    }
+
+    public static long getBlockKey(final BlockPos pos) {
+        return ((long)pos.getX() & 0x7FFFFFF) | (((long)pos.getZ() & 0x7FFFFFF) << 27) | ((long)pos.getY() << 54);
+    }
+
+    public static long getBlockKey(final Entity entity) {
+        return ((long)entity.getX() & 0x7FFFFFF) | (((long)entity.getZ() & 0x7FFFFFF) << 27) | ((long)entity.getY() << 54);
+    }
+
+    private CoordinateUtils() {
+        throw new RuntimeException();
+    }
+}
diff --git a/src/main/java/ca/spottedleaf/starlight/common/util/IntegerUtil.java b/src/main/java/ca/spottedleaf/starlight/common/util/IntegerUtil.java
new file mode 100644
index 0000000000000000000000000000000000000000..fabf1e97c019c7365212f40018dcd08d3b828113
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/starlight/common/util/IntegerUtil.java
@@ -0,0 +1,242 @@
+package ca.spottedleaf.starlight.common.util;
+
+public final class IntegerUtil {
+
+    public static final int HIGH_BIT_U32 = Integer.MIN_VALUE;
+    public static final long HIGH_BIT_U64 = Long.MIN_VALUE;
+
+    public static int ceilLog2(final int value) {
+        return Integer.SIZE - Integer.numberOfLeadingZeros(value - 1); // see doc of numberOfLeadingZeros
+    }
+
+    public static long ceilLog2(final long value) {
+        return Long.SIZE - Long.numberOfLeadingZeros(value - 1); // see doc of numberOfLeadingZeros
+    }
+
+    public static int floorLog2(final int value) {
+        // xor is optimized subtract for 2^n -1
+        // note that (2^n -1) - k = (2^n -1) ^ k for k <= (2^n - 1)
+        return (Integer.SIZE - 1) ^ Integer.numberOfLeadingZeros(value); // see doc of numberOfLeadingZeros
+    }
+
+    public static int floorLog2(final long value) {
+        // xor is optimized subtract for 2^n -1
+        // note that (2^n -1) - k = (2^n -1) ^ k for k <= (2^n - 1)
+        return (Long.SIZE - 1) ^ Long.numberOfLeadingZeros(value); // see doc of numberOfLeadingZeros
+    }
+
+    public static int roundCeilLog2(final int value) {
+        // optimized variant of 1 << (32 - leading(val - 1))
+        // given
+        // 1 << n = HIGH_BIT_32 >>> (31 - n) for n [0, 32)
+        // 1 << (32 - leading(val - 1)) = HIGH_BIT_32 >>> (31 - (32 - leading(val - 1)))
+        // HIGH_BIT_32 >>> (31 - (32 - leading(val - 1)))
+        // HIGH_BIT_32 >>> (31 - 32 + leading(val - 1))
+        // HIGH_BIT_32 >>> (-1 + leading(val - 1))
+        return HIGH_BIT_U32 >>> (Integer.numberOfLeadingZeros(value - 1) - 1);
+    }
+
+    public static long roundCeilLog2(final long value) {
+        // see logic documented above
+        return HIGH_BIT_U64 >>> (Long.numberOfLeadingZeros(value - 1) - 1);
+    }
+
+    public static int roundFloorLog2(final int value) {
+        // optimized variant of 1 << (31 - leading(val))
+        // given
+        // 1 << n = HIGH_BIT_32 >>> (31 - n) for n [0, 32)
+        // 1 << (31 - leading(val)) = HIGH_BIT_32 >> (31 - (31 - leading(val)))
+        // HIGH_BIT_32 >> (31 - (31 - leading(val)))
+        // HIGH_BIT_32 >> (31 - 31 + leading(val))
+        return HIGH_BIT_U32 >>> Integer.numberOfLeadingZeros(value);
+    }
+
+    public static long roundFloorLog2(final long value) {
+        // see logic documented above
+        return HIGH_BIT_U64 >>> Long.numberOfLeadingZeros(value);
+    }
+
+    public static boolean isPowerOfTwo(final int n) {
+        // 2^n has one bit
+        // note: this rets true for 0 still
+        return IntegerUtil.getTrailingBit(n) == n;
+    }
+
+    public static boolean isPowerOfTwo(final long n) {
+        // 2^n has one bit
+        // note: this rets true for 0 still
+        return IntegerUtil.getTrailingBit(n) == n;
+    }
+
+    public static int getTrailingBit(final int n) {
+        return -n & n;
+    }
+
+    public static long getTrailingBit(final long n) {
+        return -n & n;
+    }
+
+    public static int trailingZeros(final int n) {
+        return Integer.numberOfTrailingZeros(n);
+    }
+
+    public static int trailingZeros(final long n) {
+        return Long.numberOfTrailingZeros(n);
+    }
+
+    // from hacker's delight (signed division magic value)
+    public static int getDivisorMultiple(final long numbers) {
+        return (int)(numbers >>> 32);
+    }
+
+    // from hacker's delight (signed division magic value)
+    public static int getDivisorShift(final long numbers) {
+        return (int)numbers;
+    }
+
+    // copied from hacker's delight (signed division magic value)
+    // http://www.hackersdelight.org/hdcodetxt/magic.c.txt
+    public static long getDivisorNumbers(final int d) {
+        final int ad = branchlessAbs(d);
+
+        if (ad < 2) {
+            throw new IllegalArgumentException("|number| must be in [2, 2^31 -1], not: " + d);
+        }
+
+        final int two31 = 0x80000000;
+        final long mask = 0xFFFFFFFFL; // mask for enforcing unsigned behaviour
+
+        /*
+         Signed usage:
+         int number;
+         long magic = getDivisorNumbers(div);
+         long mul = magic >>> 32;
+         int sign = number >> 31;
+         int result = (int)(((long)number * mul) >>> magic) - sign;
+         */
+        /*
+         Unsigned usage:
+         int number;
+         long magic = getDivisorNumbers(div);
+         long mul = magic >>> 32;
+         int result = (int)(((long)number * mul) >>> magic);
+         */
+
+        int p = 31;
+
+        // all these variables are UNSIGNED!
+        int t = two31 + (d >>> 31);
+        int anc = t - 1 - (int)((t & mask)%ad);
+        int q1 = (int)((two31 & mask)/(anc & mask));
+        int r1 = two31 - q1*anc;
+        int q2 = (int)((two31 & mask)/(ad & mask));
+        int r2 = two31 - q2*ad;
+        int delta;
+
+        do {
+            p = p + 1;
+            q1 = 2*q1;                        // Update q1 = 2**p/|nc|.
+            r1 = 2*r1;                        // Update r1 = rem(2**p, |nc|).
+            if ((r1 & mask) >= (anc & mask)) {// (Must be an unsigned comparison here)
+                q1 = q1 + 1;
+                r1 = r1 - anc;
+            }
+            q2 = 2*q2;                       // Update q2 = 2**p/|d|.
+            r2 = 2*r2;                       // Update r2 = rem(2**p, |d|).
+            if ((r2 & mask) >= (ad & mask)) {// (Must be an unsigned comparison here)
+                q2 = q2 + 1;
+                r2 = r2 - ad;
+            }
+            delta = ad - r2;
+        } while ((q1 & mask) < (delta & mask) || (q1 == delta && r1 == 0));
+
+        int magicNum = q2 + 1;
+        if (d < 0) {
+            magicNum = -magicNum;
+        }
+        int shift = p;
+        return ((long)magicNum << 32) | shift;
+    }
+
+    public static int branchlessAbs(final int val) {
+        // -n = -1 ^ n + 1
+        final int mask = val >> (Integer.SIZE - 1); // -1 if < 0, 0 if >= 0
+        return (mask ^ val) - mask; // if val < 0, then (0 ^ val) - 0 else (-1 ^ val) + 1
+    }
+
+    public static long branchlessAbs(final long val) {
+        // -n = -1 ^ n + 1
+        final long mask = val >> (Long.SIZE - 1); // -1 if < 0, 0 if >= 0
+        return (mask ^ val) - mask; // if val < 0, then (0 ^ val) - 0 else (-1 ^ val) + 1
+    }
+
+    //https://github.com/skeeto/hash-prospector for hash functions
+
+    //score = ~590.47984224483832
+    public static int hash0(int x) {
+        x *= 0x36935555;
+        x ^= x >>> 16;
+        return x;
+    }
+
+    //score = ~310.01596637036749
+    public static int hash1(int x) {
+        x ^= x >>> 15;
+        x *= 0x356aaaad;
+        x ^= x >>> 17;
+        return x;
+    }
+
+    public static int hash2(int x) {
+        x ^= x >>> 16;
+        x *= 0x7feb352d;
+        x ^= x >>> 15;
+        x *= 0x846ca68b;
+        x ^= x >>> 16;
+        return x;
+    }
+
+    public static int hash3(int x) {
+        x ^= x >>> 17;
+        x *= 0xed5ad4bb;
+        x ^= x >>> 11;
+        x *= 0xac4c1b51;
+        x ^= x >>> 15;
+        x *= 0x31848bab;
+        x ^= x >>> 14;
+        return x;
+    }
+
+    //score = ~365.79959673201887
+    public static long hash1(long x) {
+        x ^= x >>> 27;
+        x *= 0xb24924b71d2d354bL;
+        x ^= x >>> 28;
+        return x;
+    }
+
+    //h2 hash
+    public static long hash2(long x) {
+        x ^= x >>> 32;
+        x *= 0xd6e8feb86659fd93L;
+        x ^= x >>> 32;
+        x *= 0xd6e8feb86659fd93L;
+        x ^= x >>> 32;
+        return x;
+    }
+
+    public static long hash3(long x) {
+        x ^= x >>> 45;
+        x *= 0xc161abe5704b6c79L;
+        x ^= x >>> 41;
+        x *= 0xe3e5389aedbc90f7L;
+        x ^= x >>> 56;
+        x *= 0x1f9aba75a52db073L;
+        x ^= x >>> 53;
+        return x;
+    }
+
+    private IntegerUtil() {
+        throw new RuntimeException();
+    }
+}
diff --git a/src/main/java/ca/spottedleaf/starlight/common/util/SaveUtil.java b/src/main/java/ca/spottedleaf/starlight/common/util/SaveUtil.java
new file mode 100644
index 0000000000000000000000000000000000000000..8d1fd22c8b8b0ea3afce6fc3e92057194f82669f
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/starlight/common/util/SaveUtil.java
@@ -0,0 +1,192 @@
+package ca.spottedleaf.starlight.common.util;
+
+import ca.spottedleaf.starlight.common.light.SWMRNibbleArray;
+import ca.spottedleaf.starlight.common.light.StarLightEngine;
+import com.mojang.logging.LogUtils;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkStatus;
+import org.slf4j.Logger;
+
+public final class SaveUtil {
+
+    private static final Logger LOGGER = LogUtils.getLogger();
+
+    private static final int STARLIGHT_LIGHT_VERSION = 9;
+
+    public static int getLightVersion() {
+        return STARLIGHT_LIGHT_VERSION;
+    }
+
+    private static final String BLOCKLIGHT_STATE_TAG = "starlight.blocklight_state";
+    private static final String SKYLIGHT_STATE_TAG = "starlight.skylight_state";
+    private static final String STARLIGHT_VERSION_TAG = "starlight.light_version";
+
+    public static void saveLightHook(final Level world, final ChunkAccess chunk, final CompoundTag nbt) {
+        try {
+            saveLightHookReal(world, chunk, nbt);
+        } catch (final Throwable ex) {
+            // failing to inject is not fatal so we catch anything here. if it fails, it will have correctly set lit to false
+            // for Vanilla to relight on load and it will not set our lit tag so we will relight on load
+            if (ex instanceof ThreadDeath) {
+                throw (ThreadDeath)ex;
+            }
+            LOGGER.warn("Failed to inject light data into save data for chunk " + chunk.getPos() + ", chunk light will be recalculated on its next load", ex);
+        }
+    }
+
+    private static void saveLightHookReal(final Level world, final ChunkAccess chunk, final CompoundTag tag) {
+        if (tag == null) {
+            return;
+        }
+
+        final int minSection = WorldUtil.getMinLightSection(world);
+        final int maxSection = WorldUtil.getMaxLightSection(world);
+
+        SWMRNibbleArray[] blockNibbles = chunk.getBlockNibbles();
+        SWMRNibbleArray[] skyNibbles = chunk.getSkyNibbles();
+
+        boolean lit = chunk.isLightCorrect() || !(world instanceof ServerLevel);
+        // diff start - store our tag for whether light data is init'd
+        if (lit) {
+            tag.putBoolean("isLightOn", false);
+        }
+        // diff end - store our tag for whether light data is init'd
+        ChunkStatus status = ChunkStatus.byName(tag.getString("Status"));
+
+        CompoundTag[] sections = new CompoundTag[maxSection - minSection + 1];
+
+        ListTag sectionsStored = tag.getList("sections", 10);
+
+        for (int i = 0; i < sectionsStored.size(); ++i) {
+            CompoundTag sectionStored = sectionsStored.getCompound(i);
+            int k = sectionStored.getByte("Y");
+
+            // strip light data
+            sectionStored.remove("BlockLight");
+            sectionStored.remove("SkyLight");
+
+            if (!sectionStored.isEmpty()) {
+                sections[k - minSection] = sectionStored;
+            }
+        }
+
+        if (lit && status.isOrAfter(ChunkStatus.LIGHT)) {
+            for (int i = minSection; i <= maxSection; ++i) {
+                SWMRNibbleArray.SaveState blockNibble = blockNibbles[i - minSection].getSaveState();
+                SWMRNibbleArray.SaveState skyNibble = skyNibbles[i - minSection].getSaveState();
+                if (blockNibble != null || skyNibble != null) {
+                    CompoundTag section = sections[i - minSection];
+                    if (section == null) {
+                        section = new CompoundTag();
+                        section.putByte("Y", (byte)i);
+                        sections[i - minSection] = section;
+                    }
+
+                    // we store under the same key so mod programs editing nbt
+                    // can still read the data, hopefully.
+                    // however, for compatibility we store chunks as unlit so vanilla
+                    // is forced to re-light them if it encounters our data. It's too much of a burden
+                    // to try and maintain compatibility with a broken and inferior skylight management system.
+
+                    if (blockNibble != null) {
+                        if (blockNibble.data != null) {
+                            section.putByteArray("BlockLight", blockNibble.data);
+                        }
+                        section.putInt(BLOCKLIGHT_STATE_TAG, blockNibble.state);
+                    }
+
+                    if (skyNibble != null) {
+                        if (skyNibble.data != null) {
+                            section.putByteArray("SkyLight", skyNibble.data);
+                        }
+                        section.putInt(SKYLIGHT_STATE_TAG, skyNibble.state);
+                    }
+                }
+            }
+        }
+
+        // rewrite section list
+        sectionsStored.clear();
+        for (CompoundTag section : sections) {
+            if (section != null) {
+                sectionsStored.add(section);
+            }
+        }
+        tag.put("sections", sectionsStored);
+        if (lit) {
+            tag.putInt(STARLIGHT_VERSION_TAG, STARLIGHT_LIGHT_VERSION); // only mark as fully lit after we have successfully injected our data
+        }
+    }
+
+    public static void loadLightHook(final Level world, final ChunkPos pos, final CompoundTag tag, final ChunkAccess into) {
+        try {
+            loadLightHookReal(world, pos, tag, into);
+        } catch (final Throwable ex) {
+            // failing to inject is not fatal so we catch anything here. if it fails, then we simply relight. Not a problem, we get correct
+            // lighting in both cases.
+            if (ex instanceof ThreadDeath) {
+                throw (ThreadDeath)ex;
+            }
+            LOGGER.warn("Failed to load light for chunk " + pos + ", light will be recalculated", ex);
+        }
+    }
+
+    private static void loadLightHookReal(final Level world, final ChunkPos pos, final CompoundTag tag, final ChunkAccess into) {
+        if (into == null) {
+            return;
+        }
+        final int minSection = WorldUtil.getMinLightSection(world);
+        final int maxSection = WorldUtil.getMaxLightSection(world);
+
+        into.setLightCorrect(false); // mark as unlit in case we fail parsing
+
+        SWMRNibbleArray[] blockNibbles = StarLightEngine.getFilledEmptyLight(world);
+        SWMRNibbleArray[] skyNibbles = StarLightEngine.getFilledEmptyLight(world);
+
+
+        // start copy from the original method
+        boolean lit = tag.get("isLightOn") != null && tag.getInt(STARLIGHT_VERSION_TAG) == STARLIGHT_LIGHT_VERSION;
+        boolean canReadSky = world.dimensionType().hasSkyLight();
+        ChunkStatus status = ChunkStatus.byName(tag.getString("Status"));
+        if (lit && status.isOrAfter(ChunkStatus.LIGHT)) { // diff - we add the status check here
+            ListTag sections = tag.getList("sections", 10);
+
+            for (int i = 0; i < sections.size(); ++i) {
+                CompoundTag sectionData = sections.getCompound(i);
+                int y = sectionData.getByte("Y");
+
+                if (sectionData.contains("BlockLight", 7)) {
+                    // this is where our diff is
+                    blockNibbles[y - minSection] = new SWMRNibbleArray(sectionData.getByteArray("BlockLight").clone(), sectionData.getInt(BLOCKLIGHT_STATE_TAG)); // clone for data safety
+                } else {
+                    blockNibbles[y - minSection] = new SWMRNibbleArray(null, sectionData.getInt(BLOCKLIGHT_STATE_TAG));
+                }
+
+                if (canReadSky) {
+                    if (sectionData.contains("SkyLight", 7)) {
+                        // we store under the same key so mod programs editing nbt
+                        // can still read the data, hopefully.
+                        // however, for compatibility we store chunks as unlit so vanilla
+                        // is forced to re-light them if it encounters our data. It's too much of a burden
+                        // to try and maintain compatibility with a broken and inferior skylight management system.
+                        skyNibbles[y - minSection] = new SWMRNibbleArray(sectionData.getByteArray("SkyLight").clone(), sectionData.getInt(SKYLIGHT_STATE_TAG)); // clone for data safety
+                    } else {
+                        skyNibbles[y - minSection] = new SWMRNibbleArray(null, sectionData.getInt(SKYLIGHT_STATE_TAG));
+                    }
+                }
+            }
+        }
+        // end copy from vanilla
+
+        into.setBlockNibbles(blockNibbles);
+        into.setSkyNibbles(skyNibbles);
+        into.setLightCorrect(lit); // now we set lit here, only after we've correctly parsed data
+    }
+
+    private SaveUtil() {}
+}
diff --git a/src/main/java/ca/spottedleaf/starlight/common/util/WorldUtil.java b/src/main/java/ca/spottedleaf/starlight/common/util/WorldUtil.java
new file mode 100644
index 0000000000000000000000000000000000000000..dd995e25ae620ae36cd5eecb2fe10ad034ba50d2
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/starlight/common/util/WorldUtil.java
@@ -0,0 +1,47 @@
+package ca.spottedleaf.starlight.common.util;
+
+import net.minecraft.world.level.LevelHeightAccessor;
+
+public final class WorldUtil {
+
+    // min, max are inclusive
+
+    public static int getMaxSection(final LevelHeightAccessor world) {
+        return world.getMaxSection() - 1; // getMaxSection() is exclusive
+    }
+
+    public static int getMinSection(final LevelHeightAccessor world) {
+        return world.getMinSection();
+    }
+
+    public static int getMaxLightSection(final LevelHeightAccessor world) {
+        return getMaxSection(world) + 1;
+    }
+
+    public static int getMinLightSection(final LevelHeightAccessor world) {
+        return getMinSection(world) - 1;
+    }
+
+
+
+    public static int getTotalSections(final LevelHeightAccessor world) {
+        return getMaxSection(world) - getMinSection(world) + 1;
+    }
+
+    public static int getTotalLightSections(final LevelHeightAccessor world) {
+        return getMaxLightSection(world) - getMinLightSection(world) + 1;
+    }
+
+    public static int getMinBlockY(final LevelHeightAccessor world) {
+        return getMinSection(world) << 4;
+    }
+
+    public static int getMaxBlockY(final LevelHeightAccessor world) {
+        return (getMaxSection(world) << 4) | 15;
+    }
+
+    private WorldUtil() {
+        throw new RuntimeException();
+    }
+
+}
diff --git a/src/main/java/io/papermc/paper/command/PaperCommand.java b/src/main/java/io/papermc/paper/command/PaperCommand.java
index 16fdfda717300a3168c27526470f83ce6239e95f..a52e6e8be323863ece6624a8ae7f9455279bdc23 100644
--- a/src/main/java/io/papermc/paper/command/PaperCommand.java
+++ b/src/main/java/io/papermc/paper/command/PaperCommand.java
@@ -39,6 +39,7 @@ public final class PaperCommand extends Command {
         commands.put(Set.of("version"), new VersionCommand());
         commands.put(Set.of("callback"), new CallbackCommand());
         commands.put(Set.of("dumpplugins"), new DumpPluginsCommand());
+        commands.put(Set.of("fixlight"), new FixLightCommand());
 
         return commands.entrySet().stream()
             .flatMap(entry -> entry.getKey().stream().map(s -> Map.entry(s, entry.getValue())))
diff --git a/src/main/java/io/papermc/paper/command/subcommands/FixLightCommand.java b/src/main/java/io/papermc/paper/command/subcommands/FixLightCommand.java
new file mode 100644
index 0000000000000000000000000000000000000000..463c6d8d5b114816ed9065558285945817c30385
--- /dev/null
+++ b/src/main/java/io/papermc/paper/command/subcommands/FixLightCommand.java
@@ -0,0 +1,115 @@
+package io.papermc.paper.command.subcommands;
+
+import io.papermc.paper.command.PaperSubcommand;
+import java.util.ArrayDeque;
+import java.util.Deque;
+import io.papermc.paper.util.MCUtil;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ChunkHolder;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.server.level.ThreadedLevelLightEngine;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.LevelChunk;
+import org.bukkit.command.CommandSender;
+import org.bukkit.craftbukkit.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+import static net.kyori.adventure.text.Component.text;
+import static net.kyori.adventure.text.format.NamedTextColor.BLUE;
+import static net.kyori.adventure.text.format.NamedTextColor.DARK_AQUA;
+import static net.kyori.adventure.text.format.NamedTextColor.GREEN;
+import static net.kyori.adventure.text.format.NamedTextColor.RED;
+
+@DefaultQualifier(NonNull.class)
+public final class FixLightCommand implements PaperSubcommand {
+    @Override
+    public boolean execute(final CommandSender sender, final String subCommand, final String[] args) {
+        this.doFixLight(sender, args);
+        return true;
+    }
+
+    private void doFixLight(final CommandSender sender, final String[] args) {
+        if (!(sender instanceof Player)) {
+            sender.sendMessage(text("Only players can use this command", RED));
+            return;
+        }
+        @Nullable Runnable post = null;
+        int radius = 2;
+        if (args.length > 0) {
+            try {
+                final int parsed = Integer.parseInt(args[0]);
+                if (parsed < 0) {
+                    sender.sendMessage(text("Radius cannot be negative!", RED));
+                    return;
+                }
+                final int maxRadius = 32;
+                radius = Math.min(maxRadius, parsed);
+                if (radius != parsed) {
+                    post = () -> sender.sendMessage(text("Radius '" + parsed + "' was not in the required range [0, " + maxRadius + "], it was lowered to the maximum (" + maxRadius + " chunks).", RED));
+                }
+            } catch (final Exception e) {
+                sender.sendMessage(text("'" + args[0] + "' is not a valid number.", RED));
+                return;
+            }
+        }
+
+        CraftPlayer player = (CraftPlayer) sender;
+        ServerPlayer handle = player.getHandle();
+        ServerLevel world = (ServerLevel) handle.level();
+        ThreadedLevelLightEngine lightengine = world.getChunkSource().getLightEngine();
+        this.starlightFixLight(handle, world, lightengine, radius, post);
+    }
+
+    private void starlightFixLight(
+        final ServerPlayer sender,
+        final ServerLevel world,
+        final ThreadedLevelLightEngine lightengine,
+        final int radius,
+        final @Nullable Runnable done
+    ) {
+        final long start = System.nanoTime();
+        final java.util.LinkedHashSet<ChunkPos> chunks = new java.util.LinkedHashSet<>(MCUtil.getSpiralOutChunks(sender.blockPosition(), radius)); // getChunkCoordinates is actually just bad mappings, this function rets position as blockpos
+
+        final int[] pending = new int[1];
+        for (java.util.Iterator<ChunkPos> iterator = chunks.iterator(); iterator.hasNext(); ) {
+            final ChunkPos chunkPos = iterator.next();
+
+            final @Nullable ChunkAccess chunk = (ChunkAccess) world.getChunkSource().getChunkForLighting(chunkPos.x, chunkPos.z);
+            if (chunk == null || !chunk.isLightCorrect() || !chunk.getStatus().isOrAfter(net.minecraft.world.level.chunk.ChunkStatus.LIGHT)) {
+                // cannot relight this chunk
+                iterator.remove();
+                continue;
+            }
+
+            ++pending[0];
+        }
+
+        final int[] relitChunks = new int[1];
+        lightengine.relight(chunks,
+            (final ChunkPos chunkPos) -> {
+                ++relitChunks[0];
+                sender.getBukkitEntity().sendMessage(text().color(DARK_AQUA).append(
+                    text("Relit chunk ", BLUE), text(chunkPos.toString()),
+                    text(", progress: ", BLUE), text((int) (Math.round(100.0 * (double) (relitChunks[0]) / (double) pending[0])) + "%")
+                ));
+            },
+            (final int totalRelit) -> {
+                final long end = System.nanoTime();
+                final long diff = Math.round(1.0e-6 * (end - start));
+                sender.getBukkitEntity().sendMessage(text().color(DARK_AQUA).append(
+                    text("Relit ", BLUE), text(totalRelit),
+                    text(" chunks. Took ", BLUE), text(diff + "ms")
+                ));
+                if (done != null) {
+                    done.run();
+                }
+            }
+        );
+        sender.getBukkitEntity().sendMessage(text().color(BLUE).append(text("Relighting "), text(pending[0], DARK_AQUA), text(" chunks")));
+    }
+}
diff --git a/src/main/java/net/minecraft/server/level/ChunkHolder.java b/src/main/java/net/minecraft/server/level/ChunkHolder.java
index 32d186fefa5ff8afedcceacea0c6fa1cefbd5490..4620e64d8eb81520b75fbfbc64603e5887c7b016 100644
--- a/src/main/java/net/minecraft/server/level/ChunkHolder.java
+++ b/src/main/java/net/minecraft/server/level/ChunkHolder.java
@@ -53,7 +53,7 @@ public class ChunkHolder {
     private volatile CompletableFuture<Either<LevelChunk, ChunkHolder.ChunkLoadingFailure>> fullChunkFuture; private int fullChunkCreateCount; private volatile boolean isFullChunkReady; // Paper - cache chunk ticking stage
     private volatile CompletableFuture<Either<LevelChunk, ChunkHolder.ChunkLoadingFailure>> tickingChunkFuture; private volatile boolean isTickingReady; // Paper - cache chunk ticking stage
     private volatile CompletableFuture<Either<LevelChunk, ChunkHolder.ChunkLoadingFailure>> entityTickingChunkFuture; private volatile boolean isEntityTickingReady; // Paper - cache chunk ticking stage
-    private CompletableFuture<ChunkAccess> chunkToSave;
+    public CompletableFuture<ChunkAccess> chunkToSave;  // Paper - public
     @Nullable
     private final DebugBuffer<ChunkHolder.ChunkSaveDebug> chunkToSaveHistory;
     public int oldTicketLevel;
diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index a645263f148a25e5b4baeed51775eb8e7f596fe8..19bd6f9aee3ccb1af1b010ee51a54aa2d0bf9c84 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -133,7 +133,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     private final LongSet entitiesInLevel;
     public final ServerLevel level;
     private final ThreadedLevelLightEngine lightEngine;
-    private final BlockableEventLoop<Runnable> mainThreadExecutor;
+    public final BlockableEventLoop<Runnable> mainThreadExecutor; // Paper - public
     public ChunkGenerator generator;
     private final RandomState randomState;
     private final ChunkGeneratorStructureState chunkGeneratorState;
diff --git a/src/main/java/net/minecraft/server/level/DistanceManager.java b/src/main/java/net/minecraft/server/level/DistanceManager.java
index d8b83c8c89143d78620f812c491a1950e3218eb1..f3c9a3dbb6f0e6f825b7477c89ed72ed52845419 100644
--- a/src/main/java/net/minecraft/server/level/DistanceManager.java
+++ b/src/main/java/net/minecraft/server/level/DistanceManager.java
@@ -386,7 +386,7 @@ public abstract class DistanceManager {
     }
 
     public void removeTicketsOnClosing() {
-        ImmutableSet<TicketType<?>> immutableset = ImmutableSet.of(TicketType.UNKNOWN, TicketType.POST_TELEPORT, TicketType.LIGHT, TicketType.FUTURE_AWAIT); // Paper - add additional tickets to preserve
+        ImmutableSet<TicketType<?>> immutableset = ImmutableSet.of(TicketType.UNKNOWN, TicketType.POST_TELEPORT, TicketType.LIGHT, TicketType.FUTURE_AWAIT, TicketType.CHUNK_RELIGHT, ca.spottedleaf.starlight.common.light.StarLightInterface.CHUNK_WORK_TICKET); // Paper - add additional tickets to preserve
         ObjectIterator objectiterator = this.tickets.long2ObjectEntrySet().fastIterator();
 
         while (objectiterator.hasNext()) {
diff --git a/src/main/java/net/minecraft/server/level/ThreadedLevelLightEngine.java b/src/main/java/net/minecraft/server/level/ThreadedLevelLightEngine.java
index 65d72701b13c25dd701533833055e77c2aff9db8..481272124b7589cff0aa05b6df5b7e6f1d539414 100644
--- a/src/main/java/net/minecraft/server/level/ThreadedLevelLightEngine.java
+++ b/src/main/java/net/minecraft/server/level/ThreadedLevelLightEngine.java
@@ -23,6 +23,17 @@ import net.minecraft.world.level.chunk.LightChunkGetter;
 import net.minecraft.world.level.lighting.LevelLightEngine;
 import org.slf4j.Logger;
 
+// Paper start
+import ca.spottedleaf.starlight.common.light.StarLightEngine;
+import io.papermc.paper.util.CoordinateUtils;
+import java.util.function.Supplier;
+import net.minecraft.world.level.lighting.LayerLightEventListener;
+import it.unimi.dsi.fastutil.longs.Long2IntOpenHashMap;
+import it.unimi.dsi.fastutil.longs.LongArrayList;
+import it.unimi.dsi.fastutil.longs.LongIterator;
+import net.minecraft.world.level.chunk.ChunkStatus;
+// Paper end
+
 public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCloseable {
     public static final int DEFAULT_BATCH_SIZE = 1000;
     private static final Logger LOGGER = LogUtils.getLogger();
@@ -33,12 +44,153 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
     private final int taskPerBatch = 1000;
     private final AtomicBoolean scheduled = new AtomicBoolean();
 
+    // Paper start - replace light engine impl
+    protected final ca.spottedleaf.starlight.common.light.StarLightInterface theLightEngine;
+    public final boolean hasBlockLight;
+    public final boolean hasSkyLight;
+    // Paper end - replace light engine impl
+
     public ThreadedLevelLightEngine(LightChunkGetter chunkProvider, ChunkMap chunkStorage, boolean hasBlockLight, ProcessorMailbox<Runnable> processor, ProcessorHandle<ChunkTaskPriorityQueueSorter.Message<Runnable>> executor) {
-        super(chunkProvider, true, hasBlockLight);
+        super(chunkProvider, false, false); // Paper - destroy vanilla light engine state
         this.chunkMap = chunkStorage;
         this.sorterMailbox = executor;
         this.taskMailbox = processor;
+        // Paper start - replace light engine impl
+        this.hasBlockLight = true;
+        this.hasSkyLight = hasBlockLight; // Nice variable name.
+        this.theLightEngine = new ca.spottedleaf.starlight.common.light.StarLightInterface(chunkProvider, this.hasSkyLight, this.hasBlockLight, this);
+        // Paper end - replace light engine impl
+    }
+
+    // Paper start - replace light engine impl
+    protected final ChunkAccess getChunk(final int chunkX, final int chunkZ) {
+        return ((ServerLevel)this.theLightEngine.getWorld()).getChunkSource().getChunkAtImmediately(chunkX, chunkZ);
+    }
+
+    protected long relightCounter;
+
+    public int relight(java.util.Set<ChunkPos> chunks_param,
+                        java.util.function.Consumer<ChunkPos> chunkLightCallback,
+                        java.util.function.IntConsumer onComplete) {
+        if (!org.bukkit.Bukkit.isPrimaryThread()) {
+            throw new IllegalStateException("Must only be called on the main thread");
+        }
+
+        java.util.Set<ChunkPos> chunks = new java.util.LinkedHashSet<>(chunks_param);
+        // add tickets
+        java.util.Map<ChunkPos, Long> ticketIds = new java.util.HashMap<>();
+        int totalChunks = 0;
+        for (java.util.Iterator<ChunkPos> iterator = chunks.iterator(); iterator.hasNext();) {
+            final ChunkPos chunkPos = iterator.next();
+
+            final ChunkAccess chunk = (ChunkAccess)((ServerLevel)this.theLightEngine.getWorld()).getChunkSource().getChunkForLighting(chunkPos.x, chunkPos.z);
+            if (chunk == null || !chunk.isLightCorrect() || !chunk.getStatus().isOrAfter(ChunkStatus.LIGHT)) {
+                // cannot relight this chunk
+                iterator.remove();
+                continue;
+            }
+
+            final Long id = Long.valueOf(this.relightCounter++);
+
+            ((ServerLevel)this.theLightEngine.getWorld()).getChunkSource().addTicketAtLevel(TicketType.CHUNK_RELIGHT, chunkPos, io.papermc.paper.util.MCUtil.getTicketLevelFor(ChunkStatus.LIGHT), id);
+            ticketIds.put(chunkPos, id);
+
+            ++totalChunks;
+        }
+
+        this.taskMailbox.tell(() -> {
+            this.theLightEngine.relightChunks(chunks, (ChunkPos chunkPos) -> {
+                chunkLightCallback.accept(chunkPos);
+                ((java.util.concurrent.Executor)((ServerLevel)this.theLightEngine.getWorld()).getChunkSource().mainThreadProcessor).execute(() -> {
+                    ((ServerLevel)this.theLightEngine.getWorld()).getChunkSource().chunkMap.getUpdatingChunkIfPresent(chunkPos.toLong()).broadcast(new net.minecraft.network.protocol.game.ClientboundLightUpdatePacket(chunkPos, ThreadedLevelLightEngine.this, null, null), false);
+                    ((ServerLevel)this.theLightEngine.getWorld()).getChunkSource().removeTicketAtLevel(TicketType.CHUNK_RELIGHT, chunkPos, io.papermc.paper.util.MCUtil.getTicketLevelFor(ChunkStatus.LIGHT), ticketIds.get(chunkPos));
+                });
+            }, onComplete);
+        });
+        this.tryScheduleUpdate();
+
+        return totalChunks;
+    }
+
+    private final Long2IntOpenHashMap chunksBeingWorkedOn = new Long2IntOpenHashMap();
+
+    private void queueTaskForSection(final int chunkX, final int chunkY, final int chunkZ, final Supplier<CompletableFuture<Void>> runnable) {
+        final ServerLevel world = (ServerLevel)this.theLightEngine.getWorld();
+
+        final ChunkAccess center = this.theLightEngine.getAnyChunkNow(chunkX, chunkZ);
+        if (center == null || !center.getStatus().isOrAfter(ChunkStatus.LIGHT)) {
+            // do not accept updates in unlit chunks, unless we might be generating a chunk. thanks to the amazing
+            // chunk scheduling, we could be lighting and generating a chunk at the same time
+            return;
+        }
+
+        if (center.getStatus() != ChunkStatus.FULL) {
+            // do not keep chunk loaded, we are probably in a gen thread
+            // if we proceed to add a ticket the chunk will be loaded, which is not what we want (avoid cascading gen)
+            runnable.get();
+            return;
+        }
+
+        if (!world.getChunkSource().chunkMap.mainThreadExecutor.isSameThread()) {
+            // ticket logic is not safe to run off-main, re-schedule
+            world.getChunkSource().chunkMap.mainThreadExecutor.execute(() -> {
+                this.queueTaskForSection(chunkX, chunkY, chunkZ, runnable);
+            });
+            return;
+        }
+
+        final long key = CoordinateUtils.getChunkKey(chunkX, chunkZ);
+
+        final CompletableFuture<Void> updateFuture = runnable.get();
+
+        if (updateFuture == null) {
+            // not scheduled
+            return;
+        }
+
+        final int references = this.chunksBeingWorkedOn.addTo(key, 1);
+        if (references == 0) {
+            final ChunkPos pos = new ChunkPos(chunkX, chunkZ);
+            world.getChunkSource().addRegionTicket(ca.spottedleaf.starlight.common.light.StarLightInterface.CHUNK_WORK_TICKET, pos, 0, pos);
+        }
+
+        updateFuture.thenAcceptAsync((final Void ignore) -> {
+            final int newReferences = this.chunksBeingWorkedOn.get(key);
+            if (newReferences == 1) {
+                this.chunksBeingWorkedOn.remove(key);
+                final ChunkPos pos = new ChunkPos(chunkX, chunkZ);
+                world.getChunkSource().removeRegionTicket(ca.spottedleaf.starlight.common.light.StarLightInterface.CHUNK_WORK_TICKET, pos, 0, pos);
+            } else {
+                this.chunksBeingWorkedOn.put(key, newReferences - 1);
+            }
+        }, world.getChunkSource().chunkMap.mainThreadExecutor).whenComplete((final Void ignore, final Throwable thr) -> {
+            if (thr != null) {
+                LOGGER.error("Failed to remove ticket level for post chunk task " + new ChunkPos(chunkX, chunkZ), thr);
+            }
+        });
+    }
+
+    @Override
+    public boolean hasLightWork() {
+        // route to new light engine
+        return this.theLightEngine.hasUpdates();
+    }
+
+    @Override
+    public LayerLightEventListener getLayerListener(final LightLayer lightType) {
+        return lightType == LightLayer.BLOCK ? this.theLightEngine.getBlockReader() : this.theLightEngine.getSkyReader();
+    }
+
+    @Override
+    public int getRawBrightness(final BlockPos pos, final int ambientDarkness) {
+        // need to use new light hooks for this
+        final int sky = this.theLightEngine.getSkyReader().getLightValue(pos) - ambientDarkness;
+        // Don't fetch the block light level if the skylight level is 15, since the value will never be higher.
+        if (sky == 15) return 15;
+        final int block = this.theLightEngine.getBlockReader().getLightValue(pos);
+        return Math.max(sky, block);
     }
+    // Paper end - replace light engine imp
 
     @Override
     public void close() {
@@ -51,15 +203,16 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
 
     @Override
     public void checkBlock(BlockPos pos) {
-        BlockPos blockPos = pos.immutable();
-        this.addTask(SectionPos.blockToSectionCoord(pos.getX()), SectionPos.blockToSectionCoord(pos.getZ()), ThreadedLevelLightEngine.TaskType.PRE_UPDATE, Util.name(() -> {
-            super.checkBlock(blockPos);
-        }, () -> {
-            return "checkBlock " + blockPos;
-        }));
+        // Paper start - replace light engine impl
+        final BlockPos posCopy = pos.immutable();
+        this.queueTaskForSection(posCopy.getX() >> 4, posCopy.getY() >> 4, posCopy.getZ() >> 4, () -> {
+            return this.theLightEngine.blockChange(posCopy);
+        });
+        // Paper end - replace light engine impl
     }
 
     protected void updateChunkStatus(ChunkPos pos) {
+        if (true) return; // Paper - replace light engine impl
         this.addTask(pos.x, pos.z, () -> {
             return 0;
         }, ThreadedLevelLightEngine.TaskType.PRE_UPDATE, Util.name(() -> {
@@ -82,17 +235,16 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
 
     @Override
     public void updateSectionStatus(SectionPos pos, boolean notReady) {
-        this.addTask(pos.x(), pos.z(), () -> {
-            return 0;
-        }, ThreadedLevelLightEngine.TaskType.PRE_UPDATE, Util.name(() -> {
-            super.updateSectionStatus(pos, notReady);
-        }, () -> {
-            return "updateSectionStatus " + pos + " " + notReady;
-        }));
+        // Paper start - replace light engine impl
+        this.queueTaskForSection(pos.getX(), pos.getY(), pos.getZ(), () -> {
+            return this.theLightEngine.sectionChange(pos, notReady);
+        });
+        // Paper end - replace light engine impl
     }
 
     @Override
     public void propagateLightSources(ChunkPos chunkPos) {
+        if (true) return; // Paper - replace light engine impl
         this.addTask(chunkPos.x, chunkPos.z, ThreadedLevelLightEngine.TaskType.PRE_UPDATE, Util.name(() -> {
             super.propagateLightSources(chunkPos);
         }, () -> {
@@ -102,6 +254,7 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
 
     @Override
     public void setLightEnabled(ChunkPos pos, boolean retainData) {
+        if (true) return; // Paper - replace light engine impl
         this.addTask(pos.x, pos.z, ThreadedLevelLightEngine.TaskType.PRE_UPDATE, Util.name(() -> {
             super.setLightEnabled(pos, retainData);
         }, () -> {
@@ -111,6 +264,7 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
 
     @Override
     public void queueSectionData(LightLayer lightType, SectionPos pos, @Nullable DataLayer nibbles) {
+        if (true) return; // Paper - replace light engine impl
         this.addTask(pos.x(), pos.z(), () -> {
             return 0;
         }, ThreadedLevelLightEngine.TaskType.PRE_UPDATE, Util.name(() -> {
@@ -136,6 +290,7 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
 
     @Override
     public void retainData(ChunkPos pos, boolean retainData) {
+        if (true) return; // Paper - replace light engine impl
         this.addTask(pos.x, pos.z, () -> {
             return 0;
         }, ThreadedLevelLightEngine.TaskType.PRE_UPDATE, Util.name(() -> {
@@ -146,6 +301,7 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
     }
 
     public CompletableFuture<ChunkAccess> initializeLight(ChunkAccess chunk, boolean bl) {
+        if (true) return CompletableFuture.completedFuture(chunk); // Paper - replace light engine impl
         ChunkPos chunkPos = chunk.getPos();
         this.addTask(chunkPos.x, chunkPos.z, ThreadedLevelLightEngine.TaskType.PRE_UPDATE, Util.name(() -> {
             LevelChunkSection[] levelChunkSections = chunk.getSections();
@@ -171,6 +327,37 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
     }
 
     public CompletableFuture<ChunkAccess> lightChunk(ChunkAccess chunk, boolean excludeBlocks) {
+        // Paper start - replace light engine impl
+        if (true) {
+            boolean lit = excludeBlocks;
+            final ChunkPos chunkPos = chunk.getPos();
+
+            return CompletableFuture.supplyAsync(() -> {
+                final Boolean[] emptySections = StarLightEngine.getEmptySectionsForChunk(chunk);
+                if (!lit) {
+                    chunk.setLightCorrect(false);
+                    this.theLightEngine.lightChunk(chunk, emptySections);
+                    chunk.setLightCorrect(true);
+                } else {
+                    this.theLightEngine.forceLoadInChunk(chunk, emptySections);
+                    // can't really force the chunk to be edged checked, as we need neighbouring chunks - but we don't have
+                    // them, so if it's not loaded then i guess we can't do edge checks. later loads of the chunk should
+                    // catch what we miss here.
+                    this.theLightEngine.checkChunkEdges(chunkPos.x, chunkPos.z);
+                }
+
+                this.chunkMap.releaseLightTicket(chunkPos);
+                return chunk;
+            }, (runnable) -> {
+                this.theLightEngine.scheduleChunkLight(chunkPos, runnable);
+                this.tryScheduleUpdate();
+            }).whenComplete((final ChunkAccess c, final Throwable throwable) -> {
+                if (throwable != null) {
+                    LOGGER.error("Failed to light chunk " + chunkPos, throwable);
+                }
+            });
+        }
+        // Paper end - replace light engine impl
         ChunkPos chunkPos = chunk.getPos();
         chunk.setLightCorrect(false);
         this.addTask(chunkPos.x, chunkPos.z, ThreadedLevelLightEngine.TaskType.PRE_UPDATE, Util.name(() -> {
@@ -191,7 +378,7 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
     }
 
     public void tryScheduleUpdate() {
-        if ((!this.lightTasks.isEmpty() || super.hasLightWork()) && this.scheduled.compareAndSet(false, true)) {
+        if (this.hasLightWork() && this.scheduled.compareAndSet(false, true)) { // Paper  // Paper - rewrite light engine
             this.taskMailbox.tell(() -> {
                 this.runUpdate();
                 this.scheduled.set(false);
@@ -213,7 +400,7 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
         }
 
         objectListIterator.back(j);
-        super.runLightUpdates();
+        this.theLightEngine.propagateChanges(); // Paper - rewrite light engine
 
         for(int var5 = 0; objectListIterator.hasNext() && var5 < i; ++var5) {
             Pair<ThreadedLevelLightEngine.TaskType, Runnable> pair2 = objectListIterator.next();
diff --git a/src/main/java/net/minecraft/server/level/TicketType.java b/src/main/java/net/minecraft/server/level/TicketType.java
index 0d536d72ac918fbd403397ff369d10143ee9c204..6051e5f272838ef23276a90e21c2fc821ca155d1 100644
--- a/src/main/java/net/minecraft/server/level/TicketType.java
+++ b/src/main/java/net/minecraft/server/level/TicketType.java
@@ -26,6 +26,7 @@ public class TicketType<T> {
     public static final TicketType<ChunkPos> UNKNOWN = TicketType.create("unknown", Comparator.comparingLong(ChunkPos::toLong), 1);
     public static final TicketType<Unit> PLUGIN = TicketType.create("plugin", (a, b) -> 0); // CraftBukkit
     public static final TicketType<org.bukkit.plugin.Plugin> PLUGIN_TICKET = TicketType.create("plugin_ticket", (plugin1, plugin2) -> plugin1.getClass().getName().compareTo(plugin2.getClass().getName())); // CraftBukkit
+    public static final TicketType<Long> CHUNK_RELIGHT = create("light_update", Long::compareTo); // Paper - ensure chunks stay loaded for lighting
 
     public static <T> TicketType<T> create(String name, Comparator<T> argumentComparator) {
         return new TicketType<>(name, argumentComparator, 0L);
diff --git a/src/main/java/net/minecraft/world/level/block/state/BlockBehaviour.java b/src/main/java/net/minecraft/world/level/block/state/BlockBehaviour.java
index 88b1aabec2812252c54d0901ccd1eba0216cb7c3..803f3ebaa9fe43c88f461168ee43fc6ba920a764 100644
--- a/src/main/java/net/minecraft/world/level/block/state/BlockBehaviour.java
+++ b/src/main/java/net/minecraft/world/level/block/state/BlockBehaviour.java
@@ -807,6 +807,7 @@ public abstract class BlockBehaviour implements FeatureElement {
             this.spawnParticlesOnBreak = blockbase_info.spawnParticlesOnBreak;
             this.instrument = blockbase_info.instrument;
             this.replaceable = blockbase_info.replaceable;
+            this.conditionallyFullOpaque = this.isOpaque() & this.isTransparentOnSomeFaces(); // Paper
         }
 
         private boolean calculateSolid() {
@@ -835,6 +836,18 @@ public abstract class BlockBehaviour implements FeatureElement {
             return this.shapeExceedsCube;
         }
         // Paper end
+        // Paper start - starlight
+        protected int opacityIfCached = -1;
+        // ret -1 if opacity is dynamic, or -1 if the block is conditionally full opaque, else return opacity in [0, 15]
+        public final int getOpacityIfCached() {
+            return this.opacityIfCached;
+        }
+
+        protected final boolean conditionallyFullOpaque;
+        public final boolean isConditionallyFullOpaque() {
+            return this.conditionallyFullOpaque;
+        }
+        // Paper end - starlight
 
         public void initCache() {
             this.fluidState = ((Block) this.owner).getFluidState(this.asState());
@@ -843,6 +856,7 @@ public abstract class BlockBehaviour implements FeatureElement {
                 this.cache = new BlockBehaviour.BlockStateBase.Cache(this.asState());
             }
             this.shapeExceedsCube = this.cache == null || this.cache.largeCollisionShape; // Paper - moved from actual method to here
+            this.opacityIfCached = this.cache == null || this.isConditionallyFullOpaque() ? -1 : this.cache.lightBlock; // Paper - starlight - cache opacity for light
 
             this.legacySolid = this.calculateSolid();
         }
diff --git a/src/main/java/net/minecraft/world/level/chunk/ChunkAccess.java b/src/main/java/net/minecraft/world/level/chunk/ChunkAccess.java
index e5e562f75e7d4b6a750f192842940c5e3af81e7d..2caac1a3d80e6c490aa16aa6bc1067065b665c69 100644
--- a/src/main/java/net/minecraft/world/level/chunk/ChunkAccess.java
+++ b/src/main/java/net/minecraft/world/level/chunk/ChunkAccess.java
@@ -86,6 +86,47 @@ public abstract class ChunkAccess implements BlockGetter, BiomeManager.NoiseBiom
     private static final org.bukkit.craftbukkit.persistence.CraftPersistentDataTypeRegistry DATA_TYPE_REGISTRY = new org.bukkit.craftbukkit.persistence.CraftPersistentDataTypeRegistry();
     public org.bukkit.craftbukkit.persistence.DirtyCraftPersistentDataContainer persistentDataContainer = new org.bukkit.craftbukkit.persistence.DirtyCraftPersistentDataContainer(ChunkAccess.DATA_TYPE_REGISTRY);
     // CraftBukkit end
+    // Paper start - rewrite light engine
+    private volatile ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] blockNibbles;
+
+    private volatile ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] skyNibbles;
+
+    private volatile boolean[] skyEmptinessMap;
+
+    private volatile boolean[] blockEmptinessMap;
+
+    public ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] getBlockNibbles() {
+        return this.blockNibbles;
+    }
+
+    public void setBlockNibbles(final ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] nibbles) {
+        this.blockNibbles = nibbles;
+    }
+
+    public ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] getSkyNibbles() {
+        return this.skyNibbles;
+    }
+
+    public void setSkyNibbles(final ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] nibbles) {
+        this.skyNibbles = nibbles;
+    }
+
+    public boolean[] getSkyEmptinessMap() {
+        return this.skyEmptinessMap;
+    }
+
+    public void setSkyEmptinessMap(final boolean[] emptinessMap) {
+        this.skyEmptinessMap = emptinessMap;
+    }
+
+    public boolean[] getBlockEmptinessMap() {
+        return this.blockEmptinessMap;
+    }
+
+    public void setBlockEmptinessMap(final boolean[] emptinessMap) {
+        this.blockEmptinessMap = emptinessMap;
+    }
+    // Paper end - rewrite light engine
 
     public ChunkAccess(ChunkPos pos, UpgradeData upgradeData, LevelHeightAccessor heightLimitView, Registry<Biome> biomeRegistry, long inhabitedTime, @Nullable LevelChunkSection[] sectionArray, @Nullable BlendingData blendingData) {
         this.locX = pos.x; this.locZ = pos.z; // Paper - reduce need for field lookups
diff --git a/src/main/java/net/minecraft/world/level/chunk/ChunkStatus.java b/src/main/java/net/minecraft/world/level/chunk/ChunkStatus.java
index d5b1fd0ff3f64675f90dd9f7f328a106e0992d51..846ae3fd184a1d63b743aa25e045604576697c96 100644
--- a/src/main/java/net/minecraft/world/level/chunk/ChunkStatus.java
+++ b/src/main/java/net/minecraft/world/level/chunk/ChunkStatus.java
@@ -260,6 +260,17 @@ public class ChunkStatus {
         return this.chunkType;
     }
 
+    // Paper start
+    public static ChunkStatus getStatus(String name) {
+        try {
+            // We need this otherwise we return EMPTY for invalid names
+            ResourceLocation key = new ResourceLocation(name);
+            return BuiltInRegistries.CHUNK_STATUS.getOptional(key).orElse(null);
+        } catch (Exception ex) {
+            return null; // invalid name
+        }
+    }
+    // Paper end
     public static ChunkStatus byName(String id) {
         return (ChunkStatus) BuiltInRegistries.CHUNK_STATUS.get(ResourceLocation.tryParse(id));
     }
diff --git a/src/main/java/net/minecraft/world/level/chunk/EmptyLevelChunk.java b/src/main/java/net/minecraft/world/level/chunk/EmptyLevelChunk.java
index ca0991b07def35b4697ba6d5569bf9a080e48a1c..f49cc61840c6588fca301b4c5c3aaeede03a323e 100644
--- a/src/main/java/net/minecraft/world/level/chunk/EmptyLevelChunk.java
+++ b/src/main/java/net/minecraft/world/level/chunk/EmptyLevelChunk.java
@@ -21,6 +21,40 @@ public class EmptyLevelChunk extends LevelChunk {
         this.biome = biomeEntry;
     }
 
+    // Paper start - starlight
+    @Override
+    public ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] getBlockNibbles() {
+        return ca.spottedleaf.starlight.common.light.StarLightEngine.getFilledEmptyLight(this.getLevel());
+    }
+
+    @Override
+    public void setBlockNibbles(final ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] nibbles) {}
+
+    @Override
+    public ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] getSkyNibbles() {
+        return ca.spottedleaf.starlight.common.light.StarLightEngine.getFilledEmptyLight(this.getLevel());
+    }
+
+    @Override
+    public void setSkyNibbles(final ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] nibbles) {}
+
+    @Override
+    public boolean[] getSkyEmptinessMap() {
+        return null;
+    }
+
+    @Override
+    public void setSkyEmptinessMap(final boolean[] emptinessMap) {}
+
+    @Override
+    public boolean[] getBlockEmptinessMap() {
+        return null;
+    }
+
+    @Override
+    public void setBlockEmptinessMap(final boolean[] emptinessMap) {}
+    // Paper end - starlight
+
     @Override
     public BlockState getBlockState(BlockPos pos) {
         return Blocks.VOID_AIR.defaultBlockState();
diff --git a/src/main/java/net/minecraft/world/level/chunk/ImposterProtoChunk.java b/src/main/java/net/minecraft/world/level/chunk/ImposterProtoChunk.java
index 6bb508105641b5729572736c5c3f9bd6711e309a..60e760b42dd6471a229dfd45490dcf8c51979d35 100644
--- a/src/main/java/net/minecraft/world/level/chunk/ImposterProtoChunk.java
+++ b/src/main/java/net/minecraft/world/level/chunk/ImposterProtoChunk.java
@@ -39,6 +39,48 @@ public class ImposterProtoChunk extends ProtoChunk {
         this.allowWrites = propagateToWrapped;
     }
 
+    // Paper start - rewrite light engine
+    @Override
+    public ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] getBlockNibbles() {
+        return this.wrapped.getBlockNibbles();
+    }
+
+    @Override
+    public void setBlockNibbles(final ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] nibbles) {
+        this.wrapped.setBlockNibbles(nibbles);
+    }
+
+    @Override
+    public ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] getSkyNibbles() {
+        return this.wrapped.getSkyNibbles();
+    }
+
+    @Override
+    public void setSkyNibbles(final ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] nibbles) {
+        this.wrapped.setSkyNibbles(nibbles);
+    }
+
+    @Override
+    public boolean[] getSkyEmptinessMap() {
+        return this.wrapped.getSkyEmptinessMap();
+    }
+
+    @Override
+    public void setSkyEmptinessMap(final boolean[] emptinessMap) {
+        this.wrapped.setSkyEmptinessMap(emptinessMap);
+    }
+
+    @Override
+    public boolean[] getBlockEmptinessMap() {
+        return this.wrapped.getBlockEmptinessMap();
+    }
+
+    @Override
+    public void setBlockEmptinessMap(final boolean[] emptinessMap) {
+        this.wrapped.setBlockEmptinessMap(emptinessMap);
+    }
+    // Paper end - rewrite light engine
+
     @Nullable
     @Override
     public BlockEntity getBlockEntity(BlockPos pos) {
diff --git a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
index 4185d524f61e87a469d563c938f742f63dad3c2f..09999a3f523ce6d652799215d3418284a69042c1 100644
--- a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
+++ b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
@@ -90,6 +90,10 @@ public class LevelChunk extends ChunkAccess {
 
     public LevelChunk(Level world, ChunkPos pos, UpgradeData upgradeData, LevelChunkTicks<Block> blockTickScheduler, LevelChunkTicks<Fluid> fluidTickScheduler, long inhabitedTime, @Nullable LevelChunkSection[] sectionArrayInitializer, @Nullable LevelChunk.PostLoadProcessor entityLoader, @Nullable BlendingData blendingData) {
         super(pos, upgradeData, world, world.registryAccess().registryOrThrow(Registries.BIOME), inhabitedTime, sectionArrayInitializer, blendingData);
+        // Paper start - rewrite light engine
+        this.setBlockNibbles(ca.spottedleaf.starlight.common.light.StarLightEngine.getFilledEmptyLight(world));
+        this.setSkyNibbles(ca.spottedleaf.starlight.common.light.StarLightEngine.getFilledEmptyLight(world));
+        // Paper end - rewrite light engine
         this.tickersInLevel = Maps.newHashMap();
         this.level = (ServerLevel) world; // CraftBukkit - type
         this.gameEventListenerRegistrySections = new Int2ObjectOpenHashMap();
@@ -219,6 +223,12 @@ public class LevelChunk extends ChunkAccess {
 
     public LevelChunk(ServerLevel world, ProtoChunk protoChunk, @Nullable LevelChunk.PostLoadProcessor entityLoader) {
         this(world, protoChunk.getPos(), protoChunk.getUpgradeData(), protoChunk.unpackBlockTicks(), protoChunk.unpackFluidTicks(), protoChunk.getInhabitedTime(), protoChunk.getSections(), entityLoader, protoChunk.getBlendingData());
+        // Paper start - rewrite light engine
+        this.setBlockNibbles(protoChunk.getBlockNibbles());
+        this.setSkyNibbles(protoChunk.getSkyNibbles());
+        this.setSkyEmptinessMap(protoChunk.getSkyEmptinessMap());
+        this.setBlockEmptinessMap(protoChunk.getBlockEmptinessMap());
+        // Paper end - rewrite light engine
         Iterator iterator = protoChunk.getBlockEntities().values().iterator();
 
         while (iterator.hasNext()) {
diff --git a/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java b/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
index afba733824d84d650e669eda028bf4d28cf006b4..cd82985b0aa821dccc0484f328407381d58ec81f 100644
--- a/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
+++ b/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
@@ -142,7 +142,7 @@ public class PalettedContainer<T> implements PaletteResize<T>, PalettedContainer
         return this.get(this.strategy.getIndex(x, y, z));
     }
 
-    protected T get(int index) {
+    public T get(int index) { // Paper - public
         PalettedContainer.Data<T> data = this.data;
         return data.palette.valueFor(data.storage.get(index));
     }
diff --git a/src/main/java/net/minecraft/world/level/chunk/ProtoChunk.java b/src/main/java/net/minecraft/world/level/chunk/ProtoChunk.java
index 38ec21faaa16df5485a81a581506700a5ab0a440..b2c0c7fd06fcd720b4c0875f08a90b6b672c96b2 100644
--- a/src/main/java/net/minecraft/world/level/chunk/ProtoChunk.java
+++ b/src/main/java/net/minecraft/world/level/chunk/ProtoChunk.java
@@ -53,6 +53,12 @@ public class ProtoChunk extends ChunkAccess {
 
     public ProtoChunk(ChunkPos pos, UpgradeData upgradeData, @Nullable LevelChunkSection[] sections, ProtoChunkTicks<Block> blockTickScheduler, ProtoChunkTicks<Fluid> fluidTickScheduler, LevelHeightAccessor world, Registry<Biome> biomeRegistry, @Nullable BlendingData blendingData) {
         super(pos, upgradeData, world, biomeRegistry, 0L, sections, blendingData);
+        // Paper start - rewrite light engine
+        if (!(this instanceof ImposterProtoChunk)) {
+            this.setBlockNibbles(ca.spottedleaf.starlight.common.light.StarLightEngine.getFilledEmptyLight(world));
+            this.setSkyNibbles(ca.spottedleaf.starlight.common.light.StarLightEngine.getFilledEmptyLight(world));
+        }
+        // Paper end - rewrite light engine
         this.blockTicks = blockTickScheduler;
         this.fluidTicks = fluidTickScheduler;
     }
diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
index cc1d7626a82881c4410d65c6a33dadae7ab07172..24892ae367e19038625e243bcdf1bb694632ede5 100644
--- a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
+++ b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
@@ -84,6 +84,14 @@ public class ChunkSerializer {
     public static final String BLOCK_LIGHT_TAG = "BlockLight";
     public static final String SKY_LIGHT_TAG = "SkyLight";
 
+    // Paper start - replace light engine impl
+    private static final int STARLIGHT_LIGHT_VERSION = 9;
+
+    private static final String BLOCKLIGHT_STATE_TAG = "starlight.blocklight_state";
+    private static final String SKYLIGHT_STATE_TAG = "starlight.skylight_state";
+    private static final String STARLIGHT_VERSION_TAG = "starlight.light_version";
+    // Paper end - replace light engine impl
+
     public ChunkSerializer() {}
 
     public static ProtoChunk read(ServerLevel world, PoiManager poiStorage, ChunkPos chunkPos, CompoundTag nbt) {
@@ -94,13 +102,20 @@ public class ChunkSerializer {
         }
 
         UpgradeData chunkconverter = nbt.contains("UpgradeData", 10) ? new UpgradeData(nbt.getCompound("UpgradeData"), world) : UpgradeData.EMPTY;
-        boolean flag = nbt.getBoolean("isLightOn");
+        boolean flag = getStatus(nbt) != null && getStatus(nbt).isOrAfter(ChunkStatus.LIGHT) && nbt.get("isLightOn") != null && nbt.getInt(STARLIGHT_VERSION_TAG) == STARLIGHT_LIGHT_VERSION; // Paper
         ListTag nbttaglist = nbt.getList("sections", 10);
         int i = world.getSectionsCount();
         LevelChunkSection[] achunksection = new LevelChunkSection[i];
         boolean flag1 = world.dimensionType().hasSkyLight();
         ServerChunkCache chunkproviderserver = world.getChunkSource();
         LevelLightEngine levellightengine = chunkproviderserver.getLightEngine();
+        // Paper start
+        ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] blockNibbles = ca.spottedleaf.starlight.common.light.StarLightEngine.getFilledEmptyLight(world);
+        ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] skyNibbles = ca.spottedleaf.starlight.common.light.StarLightEngine.getFilledEmptyLight(world);
+        final int minSection = io.papermc.paper.util.WorldUtil.getMinLightSection(world);
+        final int maxSection = io.papermc.paper.util.WorldUtil.getMaxLightSection(world);
+        boolean canReadSky = world.dimensionType().hasSkyLight();
+        // Paper end
         Registry<Biome> iregistry = world.registryAccess().registryOrThrow(Registries.BIOME);
         Codec<PalettedContainer<Holder<Biome>>> codec = ChunkSerializer.makeBiomeCodecRW(iregistry); // CraftBukkit - read/write
         boolean flag2 = false;
@@ -108,7 +123,7 @@ public class ChunkSerializer {
         DataResult dataresult;
 
         for (int j = 0; j < nbttaglist.size(); ++j) {
-            CompoundTag nbttagcompound1 = nbttaglist.getCompound(j);
+            CompoundTag nbttagcompound1 = nbttaglist.getCompound(j); CompoundTag sectionData = nbttagcompound1; // Paper
             byte b0 = nbttagcompound1.getByte("Y");
             int k = world.getSectionIndexFromSectionY(b0);
 
@@ -151,19 +166,39 @@ public class ChunkSerializer {
             boolean flag3 = nbttagcompound1.contains("BlockLight", 7);
             boolean flag4 = flag1 && nbttagcompound1.contains("SkyLight", 7);
 
-            if (flag3 || flag4) {
-                if (!flag2) {
-                    levellightengine.retainData(chunkPos, true);
-                    flag2 = true;
-                }
-
+            // Paper start - rewrite the light engine
+            if (flag) {
+                try {
+                int y = sectionData.getByte("Y");
+                // Paper end - rewrite the light engine
                 if (flag3) {
-                    levellightengine.queueSectionData(LightLayer.BLOCK, SectionPos.of(chunkPos, b0), new DataLayer(nbttagcompound1.getByteArray("BlockLight")));
+                    // Paper start - rewrite the light engine
+                    // this is where our diff is
+                    blockNibbles[y - minSection] = new ca.spottedleaf.starlight.common.light.SWMRNibbleArray(sectionData.getByteArray("BlockLight").clone(), sectionData.getInt(BLOCKLIGHT_STATE_TAG)); // clone for data safety
+                } else {
+                    blockNibbles[y - minSection] = new ca.spottedleaf.starlight.common.light.SWMRNibbleArray(null, sectionData.getInt(BLOCKLIGHT_STATE_TAG));
+                    // Paper end - rewrite the light engine
                 }
 
                 if (flag4) {
-                    levellightengine.queueSectionData(LightLayer.SKY, SectionPos.of(chunkPos, b0), new DataLayer(nbttagcompound1.getByteArray("SkyLight")));
+                    // Paper start - rewrite the light engine
+                    // we store under the same key so mod programs editing nbt
+                    // can still read the data, hopefully.
+                    // however, for compatibility we store chunks as unlit so vanilla
+                    // is forced to re-light them if it encounters our data. It's too much of a burden
+                    // to try and maintain compatibility with a broken and inferior skylight management system.
+                    skyNibbles[y - minSection] = new ca.spottedleaf.starlight.common.light.SWMRNibbleArray(sectionData.getByteArray("SkyLight").clone(), sectionData.getInt(SKYLIGHT_STATE_TAG)); // clone for data safety
+                } else if (flag1) {
+                    skyNibbles[y - minSection] = new ca.spottedleaf.starlight.common.light.SWMRNibbleArray(null, sectionData.getInt(SKYLIGHT_STATE_TAG));
+                    // Paper end - rewrite the light engine
+                }
+
+                // Paper start - rewrite the light engine
+                } catch (Exception ex) {
+                    LOGGER.warn("Failed to load light data for chunk " + chunkPos + " in world '" + world.getWorld().getName() + "', light will be regenerated", ex);
+                    flag = false;
                 }
+                // Paper end - rewrite light engine
             }
         }
 
@@ -192,6 +227,8 @@ public class ChunkSerializer {
             }, chunkPos);
 
             object1 = new LevelChunk(world.getLevel(), chunkPos, chunkconverter, levelchunkticks, levelchunkticks1, l, achunksection, ChunkSerializer.postLoadChunk(world, nbt), blendingdata);
+            ((LevelChunk)object1).setBlockNibbles(blockNibbles); // Paper - replace light impl
+            ((LevelChunk)object1).setSkyNibbles(skyNibbles); // Paper - replace light impl
         } else {
             ProtoChunkTicks<Block> protochunkticklist = ProtoChunkTicks.load(nbt.getList("block_ticks", 10), (s) -> {
                 return BuiltInRegistries.BLOCK.getOptional(ResourceLocation.tryParse(s));
@@ -200,6 +237,8 @@ public class ChunkSerializer {
                 return BuiltInRegistries.FLUID.getOptional(ResourceLocation.tryParse(s));
             }, chunkPos);
             ProtoChunk protochunk = new ProtoChunk(chunkPos, chunkconverter, achunksection, protochunkticklist, protochunkticklist1, world, iregistry, blendingdata);
+            protochunk.setBlockNibbles(blockNibbles); // Paper - replace light impl
+            protochunk.setSkyNibbles(skyNibbles); // Paper - replace light impl
 
             object1 = protochunk;
             protochunk.setInhabitedTime(l);
@@ -314,6 +353,12 @@ public class ChunkSerializer {
     // CraftBukkit end
 
     public static CompoundTag write(ServerLevel world, ChunkAccess chunk) {
+        // Paper start - rewrite light impl
+        final int minSection = io.papermc.paper.util.WorldUtil.getMinLightSection(world);
+        final int maxSection = io.papermc.paper.util.WorldUtil.getMaxLightSection(world);
+        ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] blockNibbles = chunk.getBlockNibbles();
+        ca.spottedleaf.starlight.common.light.SWMRNibbleArray[] skyNibbles = chunk.getSkyNibbles();
+        // Paper end - rewrite light impl
         ChunkPos chunkcoordintpair = chunk.getPos();
         CompoundTag nbttagcompound = NbtUtils.addCurrentDataVersion(new CompoundTag());
 
@@ -363,11 +408,14 @@ public class ChunkSerializer {
         for (int i = lightenginethreaded.getMinLightSection(); i < lightenginethreaded.getMaxLightSection(); ++i) {
             int j = chunk.getSectionIndexFromSectionY(i);
             boolean flag1 = j >= 0 && j < achunksection.length;
-            DataLayer nibblearray = lightenginethreaded.getLayerListener(LightLayer.BLOCK).getDataLayerData(SectionPos.of(chunkcoordintpair, i));
-            DataLayer nibblearray1 = lightenginethreaded.getLayerListener(LightLayer.SKY).getDataLayerData(SectionPos.of(chunkcoordintpair, i));
+            // Paper - replace light engine
 
-            if (flag1 || nibblearray != null || nibblearray1 != null) {
-                CompoundTag nbttagcompound1 = new CompoundTag();
+            // Paper start - replace light engine
+            ca.spottedleaf.starlight.common.light.SWMRNibbleArray.SaveState blockNibble = blockNibbles[i - minSection].getSaveState();
+            ca.spottedleaf.starlight.common.light.SWMRNibbleArray.SaveState skyNibble = skyNibbles[i - minSection].getSaveState();
+            if (flag1 || blockNibble != null || skyNibble != null) {
+                // Paper end - replace light engine
+                CompoundTag nbttagcompound1 = new CompoundTag(); CompoundTag section = nbttagcompound1; // Paper
 
                 if (flag1) {
                     LevelChunkSection chunksection = achunksection[j];
@@ -382,13 +430,27 @@ public class ChunkSerializer {
                     nbttagcompound1.put("biomes", (Tag) dataresult1.getOrThrow(false, logger1::error));
                 }
 
-                if (nibblearray != null && !nibblearray.isEmpty()) {
-                    nbttagcompound1.putByteArray("BlockLight", nibblearray.getData());
+                // Paper start
+                // we store under the same key so mod programs editing nbt
+                // can still read the data, hopefully.
+                // however, for compatibility we store chunks as unlit so vanilla
+                // is forced to re-light them if it encounters our data. It's too much of a burden
+                // to try and maintain compatibility with a broken and inferior skylight management system.
+
+                if (blockNibble != null) {
+                    if (blockNibble.data != null) {
+                        section.putByteArray("BlockLight", blockNibble.data);
+                    }
+                    section.putInt(BLOCKLIGHT_STATE_TAG, blockNibble.state);
                 }
 
-                if (nibblearray1 != null && !nibblearray1.isEmpty()) {
-                    nbttagcompound1.putByteArray("SkyLight", nibblearray1.getData());
+                if (skyNibble != null) {
+                    if (skyNibble.data != null) {
+                        section.putByteArray("SkyLight", skyNibble.data);
+                    }
+                    section.putInt(SKYLIGHT_STATE_TAG, skyNibble.state);
                 }
+                // Paper end
 
                 if (!nbttagcompound1.isEmpty()) {
                     nbttagcompound1.putByte("Y", (byte) i);
@@ -399,7 +461,8 @@ public class ChunkSerializer {
 
         nbttagcompound.put("sections", nbttaglist);
         if (flag) {
-            nbttagcompound.putBoolean("isLightOn", true);
+            nbttagcompound.putInt(STARLIGHT_VERSION_TAG, STARLIGHT_LIGHT_VERSION); // Paper
+            nbttagcompound.putBoolean("isLightOn", false); // Paper - set to false but still store, this allows us to detect --eraseCache (as eraseCache _removes_)
         }
 
         ListTag nbttaglist1 = new ListTag();
@@ -473,6 +536,17 @@ public class ChunkSerializer {
         }));
     }
 
+    // Paper start
+    public static @Nullable ChunkStatus getStatus(@Nullable CompoundTag compound) {
+        if (compound == null) {
+            return null;
+        }
+
+        // Note: Copied from below
+        return ChunkStatus.getStatus(compound.getString("Status"));
+    }
+    // Paper end
+
     public static ChunkStatus.ChunkType getChunkTypeFromTag(@Nullable CompoundTag nbt) {
         return nbt != null ? ChunkStatus.byName(nbt.getString("Status")).getChunkType() : ChunkStatus.ChunkType.PROTOCHUNK;
     }