Yatopia/patches/server/0035-lithium-collision-optimizations.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: JellySquid <jellysquid+atwork@protonmail.com>
Date: Thu, 20 Aug 2020 15:26:53 +0300
Subject: [PATCH] lithium collision optimizations

Original code by JellySquid, licensed under LGPLv3
you can find the original code on https://github.com/jellysquid3/lithium-fabric/ (Yarn mappings)

Co-authored-by: Ivan Pekov <ivan@mrivanplays.com>

diff --git a/src/main/java/me/jellysquid/mods/lithium/common/entity/EntityClassGroup.java b/src/main/java/me/jellysquid/mods/lithium/common/entity/EntityClassGroup.java
new file mode 100644
index 0000000000000000000000000000000000000000..91608928dc5cd2f600f1ce57ef7931078f354ea6
--- /dev/null
+++ b/src/main/java/me/jellysquid/mods/lithium/common/entity/EntityClassGroup.java
@@ -0,0 +1,101 @@
+package me.jellysquid.mods.lithium.common.entity;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.function.Function;
+import net.minecraft.server.Entity;
+
+/**
+ * Class for grouping Entity classes that meet some requirement for use in TypeFilterableList
+ * Designed to allow create groups of entity classes that are updated when mods add new entities that fit into the group.
+ *
+ * @author 2No2Name
+ */
+public class EntityClassGroup {
+    //Keep a set of classes that were already added to matching class groups, so we only analyse them once.
+    private static final Map<Class<?>, Object> knownEntityClasses = new ConcurrentHashMap<>(); //value unused, no set variant available
+    //Keep track of available class groups for updating them in case an entity class is instantiated for the first time
+    private static final List<EntityClassGroup> entityClassGroups = new net.yatopia.server.list.GlueList<>(); // Yatopia - GlueList
+
+    public static final EntityClassGroup COLLISION_BOX_OVERRIDE = new EntityClassGroup(
+            (entityClass) -> {
+                boolean overwritten;
+                while (entityClass != null && entityClass != Entity.class) {
+                    try {
+                        overwritten = true;
+                        entityClass.getDeclaredMethod("aY");
+                    } catch (NoSuchMethodException e) {
+                        overwritten = false;
+                        entityClass = entityClass.getSuperclass();
+                    }
+                    if (overwritten) {
+                        return true;
+                    }
+                }
+                return false;
+            }
+    );
+    public static final EntityClassGroup HARD_COLLISION_BOX_OVERRIDE = new EntityClassGroup(
+            (entityClass) -> {
+                boolean overwritten;
+                while (entityClass != null && entityClass != Entity.class) {
+                    try {
+                        overwritten = true;
+                        entityClass.getDeclaredMethod("j", Entity.class);
+                    } catch (NoSuchMethodException e) {
+                        overwritten = false;
+                        entityClass = entityClass.getSuperclass();
+                    }
+                    if (overwritten)
+                        return true;
+                }
+                return false;
+            }
+    );
+
+    private final Map<Class<?>, Object> classGroup; //value unused, no set variant available
+    private final Function<Class<?>, Boolean> classFitEvaluator;
+
+    public EntityClassGroup(Function<Class<?>, Boolean> classFitEvaluator) {
+        this.classGroup = new ConcurrentHashMap<>();
+        EntityClassGroup.entityClassGroups.add(this);
+        this.classFitEvaluator = classFitEvaluator;
+    }
+
+    public EntityClassGroup add(Class<?> entityClass) {
+        this.classGroup.put(entityClass, entityClass);
+        return this;
+    }
+
+    public boolean contains(Class<?> entityClass) {
+        EntityClassGroup.analyseEntityClass(entityClass);
+        return this.classGroup.containsKey(entityClass);
+    }
+
+    public Collection<Class<?>> getCollection() {
+        return this.classGroup.keySet();
+    }
+
+    public void addClassIfFitting(Class<?> discoveredEntityClass) {
+        if (this.classGroup.containsKey(discoveredEntityClass)) {
+            return;
+        }
+        if (this.classFitEvaluator != null && this.classFitEvaluator.apply(discoveredEntityClass)) {
+            this.classGroup.put(discoveredEntityClass, discoveredEntityClass);
+        }
+    }
+
+    public static void analyseEntityClass(Class<?> entityClass) {
+        if (EntityClassGroup.knownEntityClasses.containsKey(entityClass)) {
+            return;
+        }
+        EntityClassGroup.knownEntityClasses.put(entityClass, entityClass);
+
+        for (EntityClassGroup entityClassGroup : EntityClassGroup.entityClassGroups) {
+            entityClassGroup.addClassIfFitting(entityClass);
+        }
+    }
+}
diff --git a/src/main/java/me/jellysquid/mods/lithium/common/entity/EntityClassGroupHelper.java b/src/main/java/me/jellysquid/mods/lithium/common/entity/EntityClassGroupHelper.java
new file mode 100644
index 0000000000000000000000000000000000000000..20f80ae80de91615ea02f0771f7c020c3e4c6d1e
--- /dev/null
+++ b/src/main/java/me/jellysquid/mods/lithium/common/entity/EntityClassGroupHelper.java
@@ -0,0 +1,32 @@
+package me.jellysquid.mods.lithium.common.entity;
+
+import java.util.List;
+import me.jellysquid.mods.lithium.common.world.WorldHelper;
+import net.minecraft.server.AxisAlignedBB;
+import net.minecraft.server.Entity;
+import net.minecraft.server.IEntityAccess;
+import net.minecraft.server.World;
+
+public class EntityClassGroupHelper {
+
+    /**
+     * Partial [VanillaCopy] Classes overriding Entity.getHardCollisionBox(Entity other) or Entity.getCollisionBox()
+     * The returned entity list is only used to call getCollisionBox and getHardCollisionBox. As most entities return null
+     * for both of these methods, getting those is not necessary. This is why we only get entities when they overwrite
+     * getCollisionBox
+     *
+     * @param entityView the world
+     * @param selection  the box the entities have to collide with
+     * @param entity     the entity that is searching for the colliding entities
+     * @return list of entities with collision boxes
+     */
+    public static List<Entity> getEntitiesWithCollisionBoxForEntity(IEntityAccess entityView, AxisAlignedBB selection, Entity entity, boolean loadChunks) {
+        if (entity != null && EntityClassGroup.HARD_COLLISION_BOX_OVERRIDE.contains(entity.getClass()) || !(entityView instanceof World)) {
+            //use vanilla code when method_30949 (previously getHardCollisionBox(Entity other)) is overwritten, as every entity could be relevant as argument of getHardCollisionBox
+            return entityView.getEntities(entity, selection);
+        } else {
+            //only get entities that overwrite method_30948 (previously getCollisionBox)
+            return WorldHelper.getEntitiesOfClassGroup((World) entityView, entity, EntityClassGroup.COLLISION_BOX_OVERRIDE, selection, loadChunks);
+        }
+    }
+}
diff --git a/src/main/java/me/jellysquid/mods/lithium/common/entity/LithiumEntityCollisions.java b/src/main/java/me/jellysquid/mods/lithium/common/entity/LithiumEntityCollisions.java
new file mode 100644
index 0000000000000000000000000000000000000000..f2e08aafd31b3adbbbcc96df6aea7a647fb8bdf8
--- /dev/null
+++ b/src/main/java/me/jellysquid/mods/lithium/common/entity/LithiumEntityCollisions.java
@@ -0,0 +1,188 @@
+package me.jellysquid.mods.lithium.common.entity;
+
+import java.util.Iterator;
+import java.util.List;
+import java.util.function.BiConsumer;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
+import java.util.stream.Stream;
+import me.jellysquid.mods.lithium.common.entity.movement.ChunkAwareBlockCollisionSweeper;
+import me.jellysquid.mods.lithium.common.util.Producer;
+import net.minecraft.server.AxisAlignedBB;
+import net.minecraft.server.Entity;
+import net.minecraft.server.ICollisionAccess;
+import net.minecraft.server.IEntityAccess;
+import net.minecraft.server.VoxelShape;
+import net.minecraft.server.VoxelShapes;
+import net.minecraft.server.WorldBorder;
+import net.yatopia.server.EntityFilter;
+
+public class LithiumEntityCollisions {
+    public static final double EPSILON = 1.0E-7D;
+
+    /**
+     * [VanillaCopy] CollisionView#getBlockCollisions(Entity, Box)
+     * This is a much, much faster implementation which uses simple collision testing against full-cube block shapes.
+     * Checks against the world border are replaced with our own optimized functions which do not go through the
+     * VoxelShape system.
+     */
+    public static Stream<VoxelShape> getBlockCollisions(ICollisionAccess world, Entity entity, AxisAlignedBB box) {
+        if (isBoxEmpty(box)) {
+            return Stream.empty();
+        }
+
+        return Producer.asStream(getBlockCollisionProducer(world, entity, box));
+    }
+
+    public static void fillBlockCollisionsList(ICollisionAccess world, List<AxisAlignedBB> filled, Entity entity, AxisAlignedBB box) {
+        if (isBoxEmpty(box)) {
+            return;
+        }
+
+        Producer.fillList(
+                getBlockCollisionProducer(world, entity, box),
+                filled,
+                (voxelShape, axisAlignedBBS) -> VoxelShapes.addBoxesToIfIntersects(voxelShape, box, axisAlignedBBS)
+        );
+    }
+
+    public static Producer<VoxelShape> getBlockCollisionProducer(ICollisionAccess world, Entity entity, AxisAlignedBB box) {
+        final ChunkAwareBlockCollisionSweeper sweeper = new ChunkAwareBlockCollisionSweeper(world, entity, box);
+
+        return consumer -> {
+            VoxelShape shape = sweeper.getNextCollidedShape();
+            if (shape != null) {
+                consumer.accept(shape);
+                return true;
+            }
+            return false;
+        };
+    }
+
+    /**
+     * See {@link LithiumEntityCollisions#getBlockCollisions(ICollisionAccess, Entity, AxisAlignedBB)}
+     *
+     * @return True if the box (possibly that of an entity's) collided with any blocks
+     */
+    public static boolean doesBoxCollideWithBlocks(ICollisionAccess world, Entity entity, AxisAlignedBB box) {
+        if (isBoxEmpty(box)) {
+            return false;
+        }
+
+        final ChunkAwareBlockCollisionSweeper sweeper = new ChunkAwareBlockCollisionSweeper(world, entity, box);
+
+        VoxelShape shape = sweeper.getNextCollidedShape();
+        return shape != null;
+    }
+
+    /**
+     * See {@link LithiumEntityCollisions#getEntityCollisions(IEntityAccess, Entity, AxisAlignedBB, Predicate)}
+     *
+     * @return True if the box (possibly that of an entity's) collided with any other entities
+     */
+    public static boolean doesBoxCollideWithEntities(IEntityAccess view, Entity entity, AxisAlignedBB box, Predicate<Entity> predicate) {
+        if (isBoxEmpty(box)) {
+            return false;
+        }
+
+        return getEntityCollisionProducer(view, entity, box.grow(EPSILON), predicate, false).computeNext(null);
+    }
+
+    /**
+     * Returns a stream of entity collision boxes.
+     */
+    public static Stream<VoxelShape> getEntityCollisions(IEntityAccess view, Entity entity, AxisAlignedBB box, Predicate<Entity> predicate) {
+        if (isBoxEmpty(box)) {
+            return Stream.empty();
+        }
+
+        return Producer.asStream(getEntityCollisionProducer(view, entity, box.grow(EPSILON), predicate, false));
+    }
+
+    public static void fillEntityCollisionsList(IEntityAccess view, Entity entity, List<AxisAlignedBB> filled, AxisAlignedBB box, boolean loadChunks) {
+        if (isBoxEmpty(box)) {
+            return;
+        }
+
+        Producer.fillList(
+                getEntityCollisionProducer(view, entity, box.grow(EPSILON), EntityFilter.getFilter(entity), loadChunks),
+                filled,
+                (voxelShape, axisAlignedBBS) -> VoxelShapes.addBoxesToIfIntersects(voxelShape, box, axisAlignedBBS)
+        );
+    }
+
+    /**
+     * [VanillaCopy] EntityView#getEntityCollisions
+     * Re-implements the function named above without stream code or unnecessary allocations. This can provide a small
+     * boost in some situations (such as heavy entity crowding) and reduces the allocation rate significantly.
+     */
+    public static Producer<VoxelShape> getEntityCollisionProducer(IEntityAccess view, Entity entity, AxisAlignedBB box, Predicate<Entity> predicate, boolean loadChunks) {
+        return new Producer<VoxelShape>() {
+            private Iterator<Entity> it;
+
+            @Override
+            public boolean computeNext(Consumer<? super VoxelShape> consumer) {
+                if (it == null) {
+                    /*
+                     * In case entity's class is overriding method_30949, all types of entities may be (=> are assumed to be) required.
+                     * Otherwise only get entities that override method_30948 are required, as other entities cannot collide.
+                     */
+                    this.it = EntityClassGroupHelper.getEntitiesWithCollisionBoxForEntity(view, box, entity, loadChunks).iterator();
+                }
+
+                while (this.it.hasNext()) {
+                    Entity otherEntity = this.it.next();
+
+                    if (!predicate.test(otherEntity)) {
+                        continue;
+                    }
+
+                    if (entity == null) {
+                        if (!otherEntity.collisionBoxIsHard()) {
+                            continue;
+                        }
+                    } else if (!entity.hardCollidesWith(otherEntity)) {
+                        continue;
+                    }
+
+                    if (consumer != null) {
+                        consumer.accept(VoxelShapes.of(otherEntity.getBoundingBox()));
+                    }
+                    return true;
+                }
+
+                return false;
+            }
+        };
+    }
+
+    /**
+     * This provides a faster check for seeing if an entity is within the world border as it avoids going through
+     * the slower shape system.
+     *
+     * @return True if the {@param box} is fully within the {@param border}, otherwise false.
+     */
+    public static boolean isWithinWorldBorder(WorldBorder border, AxisAlignedBB box) {
+        double wboxMinX = Math.floor(border.getMinX());
+        double wboxMinZ = Math.floor(border.getMinZ());
+
+        double wboxMaxX = Math.ceil(border.getMaxX());
+        double wboxMaxZ = Math.ceil(border.getMaxZ());
+
+        return box.minX >= wboxMinX && box.minX < wboxMaxX && box.minZ >= wboxMinZ && box.minZ < wboxMaxZ &&
+                box.maxX >= wboxMinX && box.maxX < wboxMaxX && box.maxZ >= wboxMinZ && box.maxZ < wboxMaxZ;
+    }
+
+    public static boolean canEntityCollideWithWorldBorder(ICollisionAccess world, Entity entity) {
+        WorldBorder border = world.getWorldBorder();
+
+        boolean isInsideBorder = isWithinWorldBorder(border, entity.getBoundingBox().shrink(EPSILON));
+        boolean isCrossingBorder = isWithinWorldBorder(border, entity.getBoundingBox().grow(EPSILON));
+
+        return !isInsideBorder && isCrossingBorder;
+    }
+
+    private static boolean isBoxEmpty(AxisAlignedBB box) {
+        return box.getAverageSideLength() <= EPSILON;
+    }
+}
diff --git a/src/main/java/me/jellysquid/mods/lithium/common/entity/movement/ChunkAwareBlockCollisionSweeper.java b/src/main/java/me/jellysquid/mods/lithium/common/entity/movement/ChunkAwareBlockCollisionSweeper.java
new file mode 100644
index 0000000000000000000000000000000000000000..7ed343cfb3130446c85dab2ca04d60f91e2c94fb
--- /dev/null
+++ b/src/main/java/me/jellysquid/mods/lithium/common/entity/movement/ChunkAwareBlockCollisionSweeper.java
@@ -0,0 +1,278 @@
+package me.jellysquid.mods.lithium.common.entity.movement;
+
+import me.jellysquid.mods.lithium.common.entity.LithiumEntityCollisions;
+import net.minecraft.server.AxisAlignedBB;
+import net.minecraft.server.BlockPosition;
+import net.minecraft.server.Blocks;
+import net.minecraft.server.Chunk;
+import net.minecraft.server.ChunkSection;
+import net.minecraft.server.Entity;
+import net.minecraft.server.IBlockData;
+import net.minecraft.server.IChunkAccess;
+import net.minecraft.server.ICollisionAccess;
+import net.minecraft.server.MathHelper;
+import net.minecraft.server.OperatorBoolean;
+import net.minecraft.server.VoxelShape;
+import net.minecraft.server.VoxelShapeCollision;
+import net.minecraft.server.VoxelShapes;
+
+import static me.jellysquid.mods.lithium.common.entity.LithiumEntityCollisions.EPSILON;
+
+/**
+ * ChunkAwareBlockCollisionSweeper iterates over blocks in one chunk section at a time. Together with the chunk
+ * section keeping track of the amount of oversized blocks inside the number of iterations can often be reduced.
+ */
+public class ChunkAwareBlockCollisionSweeper {
+    private static final boolean OVERSIZED_BLOCK_COUNTING_ENABLED = OversizedBlocksCounter.class.isAssignableFrom(ChunkSection.class);
+
+    private final BlockPosition.MutableBlockPosition pos = new BlockPosition.MutableBlockPosition();
+
+    /**
+     * The collision box being swept through the world.
+     */
+    private final AxisAlignedBB box;
+
+    /**
+     * The VoxelShape of the collision box being swept through the world.
+     */
+    private final VoxelShape shape;
+
+    private final ICollisionAccess view;
+    private final VoxelShapeCollision context;
+
+    private final Entity entity;
+
+    //limits of the area without extension for oversized blocks
+    private final int minX, minY, minZ, maxX, maxY, maxZ;
+
+    //variables prefixed with c refer to the iteration of the currently cached chunk section
+    private int chunkX, chunkY, chunkZ;
+    private int cStartX, cStartZ;
+    private int cEndX, cEndZ;
+    private int cX, cY, cZ;
+
+    private int cTotalSize;
+    private int cIterated;
+
+    private boolean sectionOversizedBlocks;
+    private IChunkAccess cachedChunk;
+    private ChunkSection cachedChunkSection;
+    private boolean needEntityCollisionCheck;
+
+    public ChunkAwareBlockCollisionSweeper(ICollisionAccess view, Entity entity, AxisAlignedBB box) {
+        this.box = box;
+        this.shape = VoxelShapes.of(box);
+        this.context = entity == null ? VoxelShapeCollision.a() : VoxelShapeCollision.a(entity);
+        this.view = view;
+        this.entity = entity;
+        this.needEntityCollisionCheck = entity != null;
+
+        this.minX = MathHelper.floor(box.minX - EPSILON);
+        this.maxX = MathHelper.floor(box.maxX + EPSILON);
+        this.minY = MathHelper.clamp((int) (box.minY - EPSILON), 0, 255);
+        this.maxY = MathHelper.clamp((int) (box.maxY + EPSILON), 0, 255);
+        this.minZ = MathHelper.floor(box.minZ - EPSILON);
+        this.maxZ = MathHelper.floor(box.maxZ + EPSILON);
+
+        this.chunkX = (this.minX - 1) >> 4;
+        this.chunkZ = (this.minZ - 1) >> 4;
+
+        this.cIterated = 0;
+        this.cTotalSize = 0;
+
+        //decrement as first nextSection call will increment it again
+        this.chunkX--;
+    }
+
+    private boolean nextSection() {
+        do {
+            do {
+                //find the coordinates of the next section inside the area expanded by 1 block on all sides
+                //note: this.minX, maxX etc are not expanded, so there are lots of +1 and -1 around.
+                if (this.cachedChunk != null && this.chunkY < 15 && this.chunkY < ((this.maxY + 1) >> 4)) {
+                    this.chunkY++;
+                    this.cachedChunkSection = this.cachedChunk.getSections()[this.chunkY];
+                } else {
+                    this.chunkY = MathHelper.clamp((this.minY - 1) >> 4, 0, 15);
+
+                    if ((this.chunkX < ((this.maxX + 1) >> 4))) {
+                        //first initialization takes this branch
+                        this.chunkX++;
+                    } else {
+                        this.chunkX = (this.minX - 1) >> 4;
+
+                        if (this.chunkZ < ((this.maxZ + 1) >> 4)) {
+                            this.chunkZ++;
+                        } else {
+                            return false; //no more sections to iterate
+                        }
+                    }
+                    //Casting to Chunk is not checked, together with other mods this could cause a ClassCastException
+                    this.cachedChunk = (IChunkAccess) this.view.c(this.chunkX, this.chunkZ);
+                    if (this.cachedChunk != null) {
+                        this.cachedChunkSection = this.cachedChunk.getSections()[this.chunkY];
+                    }
+                }
+                //skip empty chunks and empty chunk sections
+            } while (this.cachedChunk == null || ChunkSection.isEmpty(this.cachedChunkSection));
+
+            this.sectionOversizedBlocks = hasChunkSectionOversizedBlocks(this.cachedChunk, this.chunkY);
+
+            int sizeExtension = this.sectionOversizedBlocks ? 1 : 0;
+
+            this.cEndX = Math.min(this.maxX + sizeExtension, 15 + (this.chunkX << 4));
+            int cEndY = Math.min(this.maxY + sizeExtension, 15 + (this.chunkY << 4));
+            this.cEndZ = Math.min(this.maxZ + sizeExtension, 15 + (this.chunkZ << 4));
+
+            this.cStartX = Math.max(this.minX - sizeExtension, this.chunkX << 4);
+            int cStartY = Math.max(this.minY - sizeExtension, this.chunkY << 4);
+            this.cStartZ = Math.max(this.minZ - sizeExtension, this.chunkZ << 4);
+            this.cX = this.cStartX;
+            this.cY = cStartY;
+            this.cZ = this.cStartZ;
+
+            this.cTotalSize = (this.cEndX - this.cStartX + 1) * (cEndY - cStartY + 1) * (this.cEndZ - this.cStartZ + 1);
+            //skip completely empty section iterations
+        } while (this.cTotalSize == 0);
+        this.cIterated = 0;
+
+        return true;
+    }
+
+    public VoxelShape getNextCollidedShape() {
+        VoxelShape shape = null;
+
+        if (this.needEntityCollisionCheck) {
+            shape = this.getNextEntityCollision();
+
+            this.needEntityCollisionCheck = false;
+        }
+
+        if (shape == null) {
+            shape = this.getNextBlockCollision();
+        }
+
+        return shape;
+    }
+
+
+    /**
+     * Advances the sweep forward until finding a block with a box-colliding VoxelShape
+     *
+     * @return null if no VoxelShape is left in the area, otherwise the next VoxelShape
+     */
+    private VoxelShape getNextBlockCollision() {
+        while (true) {
+            if (this.cIterated >= this.cTotalSize) {
+                if (!this.nextSection()) {
+                    break;
+                }
+            }
+            this.cIterated++;
+
+
+            final int x = this.cX;
+            final int y = this.cY;
+            final int z = this.cZ;
+
+            //The iteration order within a chunk section is chosen so that it causes a mostly linear array access in the storage.
+            //In net.minecraft.world.chunk.PalettedContainer.toIndex x gets the 4 least significant bits, z the 4 above, and y the 4 even higher ones.
+            //Linearly accessing arrays might be slightly faster than other access patterns.
+            //This code hasn't been benchmarked in comparison to another access order.
+            if (this.cX < this.cEndX) {
+                this.cX++;
+            } else if (this.cZ < this.cEndZ) {
+                this.cX = this.cStartX;
+                this.cZ++;
+            } else {
+                this.cX = this.cStartX;
+                this.cZ = this.cStartZ;
+                this.cY++;
+                //stop condition was already checked using this.cIterated at the start of the method
+            }
+
+            //using < minX and > maxX instead of <= and >= in vanilla, because minX, maxX are the coordinates
+            //of the box that wasn't extended for oversized blocks yet.
+            final int edgesHit = this.sectionOversizedBlocks ?
+                    (x < this.minX || x > this.maxX ? 1 : 0) +
+                            (y < this.minY || y > this.maxY ? 1 : 0) +
+                            (z < this.minZ || z > this.maxZ ? 1 : 0) : 0;
+
+            if (edgesHit == 3) {
+                continue;
+            }
+
+            final IBlockData state = this.cachedChunkSection.getType(x & 15, y & 15, z & 15);
+
+            if (canInteractWithBlock(state, edgesHit)) {
+                this.pos.setValues(x, y, z);
+                VoxelShape collisionShape = state.getCollisionShape(this.view, this.pos, this.context);
+
+                if (collisionShape != VoxelShapes.empty()) {
+                    VoxelShape collidedShape = getCollidedShape(this.box, this.shape, collisionShape, x, y, z);
+                    if (collidedShape != null) {
+                        return collidedShape;
+                    }
+                }
+            }
+        }
+
+        return null;
+    }
+
+    private VoxelShape getNextEntityCollision() {
+        if (LithiumEntityCollisions.canEntityCollideWithWorldBorder(this.view, this.entity)) {
+            return this.view.getWorldBorder().asVoxelShape();
+        }
+
+        return null;
+    }
+
+    /**
+     * This is an artifact from vanilla which is used to avoid testing shapes in the extended portion of a volume
+     * unless they are a shape which exceeds their voxel. Pistons must be special-cased here.
+     *
+     * @return True if the shape can be interacted with at the given edge boundary
+     */
+    private static boolean canInteractWithBlock(IBlockData state, int edgesHit) {
+        return (edgesHit != 1 || state.shapeExceedsCube()) && (edgesHit != 2 || state.getBlock() == Blocks.MOVING_PISTON);
+    }
+
+    /**
+     * Checks if the {@param entityShape} or {@param entityBox} intersects the given {@param shape} which is translated
+     * to the given position. This is a very specialized implementation which tries to avoid going through VoxelShape
+     * for full-cube shapes.
+     *
+     * @return A {@link VoxelShape} which contains the shape representing that which was collided with, otherwise null
+     */
+    private static VoxelShape getCollidedShape(AxisAlignedBB entityBox, VoxelShape entityShape, VoxelShape shape, int x, int y, int z) {
+        if (shape.intersects(entityBox)) {
+            return shape.offset(x, y, z);
+        } else {
+            shape = shape.offset(x, y, z);
+
+            if (VoxelShapes.applyOperation(shape, entityShape, OperatorBoolean.AND)) {
+                return shape;
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * Checks the cached information whether the {@param chunkY} section of the {@param chunk} has oversized blocks.
+     *
+     * @return Whether there are any oversized blocks in the chunk section.
+     */
+    private static boolean hasChunkSectionOversizedBlocks(IChunkAccess chunk, int chunkY) {
+        if (OVERSIZED_BLOCK_COUNTING_ENABLED) {
+            ChunkSection section = chunk.getSections()[chunkY];
+            return section != null && ((OversizedBlocksCounter) section).hasOversizedBlocks();
+        }
+        return true; //like vanilla, assume that a chunk section has oversized blocks, when the section mixin isn't loaded
+    }
+
+    public interface OversizedBlocksCounter {
+        boolean hasOversizedBlocks();
+    }
+}
diff --git a/src/main/java/me/jellysquid/mods/lithium/common/util/Producer.java b/src/main/java/me/jellysquid/mods/lithium/common/util/Producer.java
new file mode 100644
index 0000000000000000000000000000000000000000..f3224ea636fef95d368b934ed4b3e9060c4b10a2
--- /dev/null
+++ b/src/main/java/me/jellysquid/mods/lithium/common/util/Producer.java
@@ -0,0 +1,55 @@
+package me.jellysquid.mods.lithium.common.util;
+
+import java.util.List;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.BiConsumer;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+import net.yatopia.server.HoldingConsumer;
+
+public interface Producer<T> {
+    /**
+     * Computes the next sequence of values in a collection. If a null value is passed for {@param consumer}, then
+     * the producer will only return whether or not elements existed.
+     *
+     * @param consumer The (nullable) consumer which will accept the computed values during this run.
+     * @return True if the producer produced any values, otherwise false
+     */
+    boolean computeNext(Consumer<? super T> consumer);
+
+    default <U> Producer<U> map(Function<T, U> mapper) {
+        return consumer -> {
+            Consumer<? super T> con = (t) -> consumer.accept(mapper.apply(t));
+            return Producer.this.computeNext(con);
+        };
+    }
+
+    static <T> Stream<T> asStream(Producer<T> producer) {
+        return StreamSupport.stream(new Spliterators.AbstractSpliterator<T>(Long.MAX_VALUE, Spliterator.ORDERED | Spliterator.NONNULL) {
+            @Override
+            public boolean tryAdvance(Consumer<? super T> action) {
+                return producer.computeNext(action);
+            }
+        }, false);
+    }
+
+    // WARNING: does not check contains, you have to do that in the add function
+    static <T, R> void fillList(Producer<T> producer, List<R> list, BiConsumer<T, List<R>> addFunction) {
+        HoldingConsumer<T> consumer = new HoldingConsumer<>();
+        while (producer.computeNext(consumer)) {
+            T value = consumer.getValue();
+            if (value == null) { continue; }
+            addFunction.accept(value, list);
+        }
+    }
+
+    Producer<?> EMPTY_PRODUCER = consumer -> false;
+
+    @SuppressWarnings("unchecked")
+    static <T> Producer<T> empty() {
+        return (Producer<T>) EMPTY_PRODUCER;
+    }
+}
diff --git a/src/main/java/me/jellysquid/mods/lithium/common/world/WorldHelper.java b/src/main/java/me/jellysquid/mods/lithium/common/world/WorldHelper.java
new file mode 100644
index 0000000000000000000000000000000000000000..f858e5dcda60391fe869264f0c4a20bb14159e82
--- /dev/null
+++ b/src/main/java/me/jellysquid/mods/lithium/common/world/WorldHelper.java
@@ -0,0 +1,59 @@
+package me.jellysquid.mods.lithium.common.world;
+
+import com.google.common.collect.Lists;
+import java.util.List;
+import me.jellysquid.mods.lithium.common.entity.EntityClassGroup;
+import me.jellysquid.mods.lithium.common.world.chunk.ClassGroupFilterableList;
+import net.minecraft.server.AxisAlignedBB;
+import net.minecraft.server.Chunk;
+import net.minecraft.server.Entity;
+import net.minecraft.server.EntitySlice;
+import net.minecraft.server.MathHelper;
+import net.minecraft.server.World;
+
+public class WorldHelper {
+
+    /**
+     * Method that allows getting entities of a class group.
+     * [VanillaCopy] but custom combination of: get class filtered entities together with excluding one entity
+     */
+    public static List<Entity> getEntitiesOfClassGroup(World world, Entity excluded, EntityClassGroup type, AxisAlignedBB box_1, boolean loadChunks) {
+        int int_1 = MathHelper.floor((box_1.minX - 2.0D) / 16.0D);
+        int int_2 = MathHelper.f((box_1.maxX + 2.0D) / 16.0D);
+        int int_3 = MathHelper.floor((box_1.minZ - 2.0D) / 16.0D);
+        int int_4 = MathHelper.f((box_1.maxZ + 2.0D) / 16.0D);
+        List<Entity> list_1 = Lists.newArrayList();
+
+        for (int int_5 = int_1; int_5 < int_2; ++int_5) {
+            for (int int_6 = int_3; int_6 < int_4; ++int_6) {
+                Chunk worldChunk_1 = loadChunks ? world.getChunkAt(int_5, int_6) : world.getChunkIfLoaded(int_5, int_6);
+                if (worldChunk_1 != null) {
+                    WorldHelper.getEntitiesOfClassGroup(worldChunk_1, excluded, type, box_1, list_1);
+                }
+            }
+        }
+
+        return list_1;
+    }
+
+    /**
+     * Method that allows getting entities of a class group.
+     * [VanillaCopy] but custom combination of: get class filtered entities together with excluding one entity
+     */
+    public static void getEntitiesOfClassGroup(Chunk worldChunk, Entity excluded, EntityClassGroup type, AxisAlignedBB box_1, List<Entity> list_1) {
+        EntitySlice<Entity>[] entitySections = worldChunk.getAsSlices();
+        int int_1 = MathHelper.floor((box_1.minY - 2.0D) / 16.0D);
+        int int_2 = MathHelper.floor((box_1.maxY + 2.0D) / 16.0D);
+        int_1 = MathHelper.clamp(int_1, 0, entitySections.length - 1);
+        int_2 = MathHelper.clamp(int_2, 0, entitySections.length - 1);
+
+        for (int int_3 = int_1; int_3 <= int_2; ++int_3) {
+            //noinspection rawtypes
+            for (Object entity_1 : ((ClassGroupFilterableList) entitySections[int_3]).getAllOfGroupType(type)) {
+                if (entity_1 != excluded && ((Entity) entity_1).getBoundingBox().intersects(box_1)) {
+                    list_1.add((Entity) entity_1);
+                }
+            }
+        }
+    }
+}
diff --git a/src/main/java/me/jellysquid/mods/lithium/common/world/chunk/ClassGroupFilterableList.java b/src/main/java/me/jellysquid/mods/lithium/common/world/chunk/ClassGroupFilterableList.java
new file mode 100644
index 0000000000000000000000000000000000000000..493103d755c222f2c6031ffb8f5c0b7a2e3fde77
--- /dev/null
+++ b/src/main/java/me/jellysquid/mods/lithium/common/world/chunk/ClassGroupFilterableList.java
@@ -0,0 +1,8 @@
+package me.jellysquid.mods.lithium.common.world.chunk;
+
+import java.util.Collection;
+import me.jellysquid.mods.lithium.common.entity.EntityClassGroup;
+
+public interface ClassGroupFilterableList<T> {
+    Collection<T> getAllOfGroupType(EntityClassGroup type);
+}
diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
index f3702ed75ebcd78075da947acf9bdc2ec0379180..cee9bd91d679a867610a88bec5b8180423d52c1e 100644
--- a/src/main/java/net/minecraft/server/Chunk.java
+++ b/src/main/java/net/minecraft/server/Chunk.java
@@ -36,7 +36,7 @@ public class Chunk implements IChunkAccess {
     public final Map<HeightMap.Type, HeightMap> heightMap;
     private final ChunkConverter i;
     public final Map<BlockPosition, TileEntity> tileEntities;
-    public final List<Entity>[] entitySlices; // Spigot
+    public final EntitySlice<Entity>[] entitySlices; // Spigot // Yatopia - md_5 is dumb
     private final Map<StructureGenerator<?>, StructureStart<?>> l;
     private final Map<StructureGenerator<?>, LongSet> m;
     private final ShortList[] n;
@@ -244,7 +244,7 @@ public class Chunk implements IChunkAccess {
         this.l = Maps.newHashMap();
         this.m = Maps.newHashMap();
         this.n = new ShortList[16];
-        this.entitySlices = (List[]) (new List[16]); // Spigot
+        this.entitySlices = new EntitySlice[16]; // Spigot // Yatopia - md_5 is stupid
         this.world = (WorldServer) world; // CraftBukkit - type
         this.loc = chunkcoordintpair; this.coordinateKey = MCUtil.getCoordinateKey(chunkcoordintpair); // Paper - cache coordinate key
         this.i = chunkconverter;
@@ -260,7 +260,7 @@ public class Chunk implements IChunkAccess {
         }
 
         for (int l = 0; l < this.entitySlices.length; ++l) {
-            this.entitySlices[l] = new org.bukkit.craftbukkit.util.UnsafeList(); // Spigot
+            this.entitySlices[l] = new EntitySlice<>(Entity.class); // Spigot // Yatopia - md_5 is stupid
         }
 
         this.d = biomestorage;
@@ -713,8 +713,8 @@ public class Chunk implements IChunkAccess {
             k = this.entitySlices.length - 1;
         }
         // Paper - remove from any old list if its in one
-        List<Entity> nextSlice = this.entitySlices[k]; // the next list to be added to
-        List<Entity> currentSlice = entity.entitySlice;
+        EntitySlice<Entity> nextSlice = this.entitySlices[k]; // the next list to be added to // Yatopia - paper not stupid, md_5 is
+        EntitySlice<Entity> currentSlice = entity.entitySlice; // Yatopia - paper not stupid, md_5 is
         if (nextSlice == currentSlice) {
             if (World.DEBUG_ENTITIES) MinecraftServer.LOGGER.warn("Entity was already in this chunk!" + entity, new Throwable());
             return; // ??? silly plugins
@@ -1028,12 +1028,12 @@ public class Chunk implements IChunkAccess {
         j = MathHelper.clamp(j, 0, this.entitySlices.length - 1);
 
         for (int k = i; k <= j; ++k) {
-            List<Entity> entityslice = this.entitySlices[k]; // Spigot
-            List<Entity> list1 = entityslice; // Spigot
+            EntitySlice<Entity> entityslice = this.entitySlices[k]; // Spigot // Yatopia - md_5 is stupid
+            EntitySlice<Entity> list1 = entityslice; // Spigot // Yatopia - md_5 is stupid
             int l = list1.size();
 
-            for (int i1 = 0; i1 < l; ++i1) {
-                Entity entity1 = (Entity) list1.get(i1);
+            for (Entity entity1 : list1) { // Yatopia
+                //Entity entity1 = (Entity) list1.get(i1); // Yatopia
                 if (entity1.shouldBeRemoved) continue; // Paper
 
                 if (entity1.getBoundingBox().c(axisalignedbb) && entity1 != entity) {
@@ -1166,8 +1166,16 @@ public class Chunk implements IChunkAccess {
     }
 
     public List<Entity>[] getEntitySlices() { // Spigot
-        return this.entitySlices;
+        // Yatopia start
+        List<Entity>[] ret = new List[entitySlices.length];
+        for (int i = 0, len = entitySlices.length; i < len; i++) {
+            EntitySlice<Entity> slice = entitySlices[i];
+            ret[i] = slice.toList();
+        }
+        return ret;
     }
+    public EntitySlice<Entity>[] getAsSlices() { return entitySlices; }
+    // Yatopia end
 
     @Override
     public NBTTagCompound i(BlockPosition blockposition) {
diff --git a/src/main/java/net/minecraft/server/ChunkRegionLoader.java b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
index 1bc8b11d999e9af16a44fe1cb62f5785afa82462..30d4589c9cdad11809fc09cb51235d6da8e03195 100644
--- a/src/main/java/net/minecraft/server/ChunkRegionLoader.java
+++ b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
@@ -503,8 +503,11 @@ public class ChunkRegionLoader {
 
             chunk.d(false);
 
-            for (int j = 0; j < chunk.getEntitySlices().length; ++j) {
-                Iterator iterator1 = chunk.getEntitySlices()[j].iterator();
+            // Yatopia start
+            EntitySlice<Entity>[] entitySlices = chunk.getAsSlices();
+            for (int j = 0; j < entitySlices.length; ++j) {
+                Iterator iterator1 = entitySlices[j].iterator();
+                // Yatopia end
 
                 while (iterator1.hasNext()) {
                     Entity entity = (Entity) iterator1.next();
diff --git a/src/main/java/net/minecraft/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index 5beca7e82b3f2a44c376ab2fedac27ce8b7fbd3a..6b96c392fb3eadd20f87675b797337d6d30cc7be 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -73,7 +73,7 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
             }
         }
     };
-    List<Entity> entitySlice = null;
+    EntitySlice<Entity> entitySlice = null; // Yatopia - change to EntitySlice
     public org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason spawnReason;
     // Paper end
 
diff --git a/src/main/java/net/minecraft/server/EntitySlice.java b/src/main/java/net/minecraft/server/EntitySlice.java
index 1250c3cbe915815939627701c153ba6254fc05f0..cdf54580a8275f40730f9cbdc1c0c4b4a3999a90 100644
--- a/src/main/java/net/minecraft/server/EntitySlice.java
+++ b/src/main/java/net/minecraft/server/EntitySlice.java
@@ -14,18 +14,35 @@ import java.util.Map.Entry;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-public class EntitySlice<T> extends AbstractCollection<T> {
+// Yatopia start
+import it.unimi.dsi.fastutil.objects.ReferenceLinkedOpenHashSet;
+import it.unimi.dsi.fastutil.objects.Reference2ReferenceArrayMap;
+import me.jellysquid.mods.lithium.common.entity.EntityClassGroup;
+// Yatopia end
+
+public class EntitySlice<T> extends AbstractCollection<T> implements me.jellysquid.mods.lithium.common.world.chunk.ClassGroupFilterableList<T> { // Yatopia
 
     private final Map<Class<?>, List<T>> a = Maps.newHashMap();
     private final Class<T> b;
-    private final List<T> c = Lists.newArrayList();
+    private final List<T> c = new net.yatopia.server.list.GlueList<>(); // Yatopia
+
+    private final Reference2ReferenceArrayMap<EntityClassGroup, ReferenceLinkedOpenHashSet<T>> entitiesByGroup; // Yatopia
 
     public EntitySlice(Class<T> oclass) {
         this.b = oclass;
         this.a.put(oclass, this.c);
+        this.entitiesByGroup = new Reference2ReferenceArrayMap<>(); // Yatopia
     }
 
     public boolean add(T t0) {
+        // Yatopia start
+        for (Map.Entry<EntityClassGroup, ReferenceLinkedOpenHashSet<T>> entityGroupAndSet : this.entitiesByGroup.entrySet()) {
+            EntityClassGroup entityGroup = entityGroupAndSet.getKey();
+            if (entityGroup.contains(((Entity)t0).getClass())) {
+                entityGroupAndSet.getValue().add((t0));
+            }
+        }
+        // Yatopia end
         boolean flag = false;
         Iterator iterator = this.a.entrySet().iterator();
 
@@ -41,6 +58,11 @@ public class EntitySlice<T> extends AbstractCollection<T> {
     }
 
     public boolean remove(Object object) {
+        // Yatopia start
+        for (Map.Entry<EntityClassGroup, ReferenceLinkedOpenHashSet<T>> entityGroupAndSet : this.entitiesByGroup.entrySet()) {
+            entityGroupAndSet.getValue().remove(object);
+        }
+        // Yatopia end
         boolean flag = false;
         Iterator iterator = this.a.entrySet().iterator();
 
@@ -61,10 +83,13 @@ public class EntitySlice<T> extends AbstractCollection<T> {
         return this.a(object.getClass()).contains(object);
     }
 
+    @SuppressWarnings("unchecked") // Yatopia
     public <S> Collection<S> a(Class<S> oclass) {
         if (!this.b.isAssignableFrom(oclass)) {
             throw new IllegalArgumentException("Don't know how to search for " + oclass);
         } else {
+            // Yatopia start - replace this
+            /*
             List<T> list = (List) this.a.computeIfAbsent(oclass, (oclass1) -> {
                 Stream stream = this.c.stream();
 
@@ -73,6 +98,18 @@ public class EntitySlice<T> extends AbstractCollection<T> {
             });
 
             return Collections.unmodifiableCollection(list);
+             */
+            if (a.containsKey(oclass)) {
+                return (Collection<S>) Collections.unmodifiableCollection(a.get(oclass));
+            }
+            List<T> list = new net.yatopia.server.list.GlueList<>();
+            for (T allElement : this.c) {
+                if (oclass.isInstance(allElement)) {
+                    list.add(allElement);
+                }
+            }
+            a.put(oclass, list);
+            return (Collection<S>) Collections.unmodifiableCollection(list);
         }
     }
 
@@ -81,10 +118,44 @@ public class EntitySlice<T> extends AbstractCollection<T> {
     }
 
     public List<T> a() {
-        return ImmutableList.copyOf(this.c);
+        return Collections.unmodifiableList(this.c); // Yatopia - avoid copying
     }
 
     public int size() {
         return this.c.size();
     }
+
+    // Yatopia start
+    @Override
+    public Collection<T> getAllOfGroupType(EntityClassGroup type) {
+        Collection<T> collection = this.entitiesByGroup.get(type);
+
+        if (collection == null) {
+            collection =  this.createAllOfGroupType(type);
+        }
+
+        return Collections.unmodifiableCollection(collection);
+    }
+
+    private Collection<T> createAllOfGroupType(EntityClassGroup type) {
+        ReferenceLinkedOpenHashSet<T> allOfType = new ReferenceLinkedOpenHashSet<>();
+
+        for (T entity : this.c) {
+            if (type.contains(entity.getClass())) {
+                allOfType.add(entity);
+            }
+        }
+        this.entitiesByGroup.put(type, allOfType);
+        return allOfType;
+    }
+
+    /**
+     * A workaround about md_5's dumb changes
+     *
+     * @return list representation of EntitySlice
+     */
+    public List<T> toList() {
+        return c;
+    }
+    // Yatopia end
 }
diff --git a/src/main/java/net/minecraft/server/ICollisionAccess.java b/src/main/java/net/minecraft/server/ICollisionAccess.java
index b66c802d5e27518069bf42e577bcc9a26c4d873e..22728e5ba8b2dd6efc3164d06ea791693de50936 100644
--- a/src/main/java/net/minecraft/server/ICollisionAccess.java
+++ b/src/main/java/net/minecraft/server/ICollisionAccess.java
@@ -52,7 +52,14 @@ public interface ICollisionAccess extends IBlockAccess {
     default boolean getCubes(@Nullable Entity entity, AxisAlignedBB axisalignedbb, Predicate<Entity> predicate) {
         // Tuinity end - allow overriding in WorldServer
         try { if (entity != null) entity.collisionLoadChunks = true; // Paper
-        return this.d(entity, axisalignedbb, predicate).allMatch(VoxelShape::isEmpty);
+            // Yatopia start
+        //return this.d(entity, axisalignedbb, predicate).allMatch(VoxelShape::isEmpty);
+            boolean ret = !me.jellysquid.mods.lithium.common.entity.LithiumEntityCollisions.doesBoxCollideWithBlocks(this, entity, axisalignedbb);
+            if (ret && this instanceof IEntityAccess) {
+                ret = !me.jellysquid.mods.lithium.common.entity.LithiumEntityCollisions.doesBoxCollideWithEntities((IEntityAccess) this, entity, axisalignedbb, predicate);
+            }
+            return ret;
+            // Yatopia end
         } finally { if (entity != null) entity.collisionLoadChunks = false; } // Paper
     }
 
@@ -63,7 +70,7 @@ public interface ICollisionAccess extends IBlockAccess {
     }
 
     default Stream<VoxelShape> b(@Nullable Entity entity, AxisAlignedBB axisalignedbb) {
-        return StreamSupport.stream(new VoxelShapeSpliterator(this, entity, axisalignedbb), false);
+        return me.jellysquid.mods.lithium.common.entity.LithiumEntityCollisions.getBlockCollisions(this, entity, axisalignedbb); // Yatopia
     }
 
     default Stream<VoxelShape> b(@Nullable Entity entity, AxisAlignedBB axisalignedbb, BiPredicate<IBlockData, BlockPosition> bipredicate) {
diff --git a/src/main/java/net/minecraft/server/IEntityAccess.java b/src/main/java/net/minecraft/server/IEntityAccess.java
index 40ca3364d462dc7b5a4c1f8f353c758a421656bf..7657d13dd7556e4c32088bbe5735df525c0b2922 100644
--- a/src/main/java/net/minecraft/server/IEntityAccess.java
+++ b/src/main/java/net/minecraft/server/IEntityAccess.java
@@ -62,6 +62,10 @@ public interface IEntityAccess {
     // Tuinity end - optimise hard collision
 
     default Stream<VoxelShape> c(@Nullable Entity entity, AxisAlignedBB axisalignedbb, Predicate<Entity> predicate) {
+        // Yatopia start - replace this
+        if (predicate == null) predicate = (e) -> true; // Tuinity - allow nullable
+        return me.jellysquid.mods.lithium.common.entity.LithiumEntityCollisions.getEntityCollisions(this, entity, axisalignedbb, predicate);
+        /*
         if (axisalignedbb.a() < 1.0E-7D) {
             return Stream.empty();
         } else {
@@ -91,6 +95,7 @@ public interface IEntityAccess {
                 return flag;
             }); return ((entity != null && entity.hardCollides()) ? this.getEntities(entity, axisalignedbb1, predicate) : this.getHardCollidingEntities(entity, axisalignedbb1, predicate)).stream().map(Entity::getBoundingBox).map(VoxelShapes::a); // Tuinity - optimise entity hard collisions
         }
+         */ // Yatopia end
     }
 
     default EntityHuman findNearbyPlayer(Entity entity, double d0, @Nullable Predicate<Entity> predicate) { return this.findNearbyPlayer(entity.locX(), entity.locY(), entity.locZ(), d0, predicate); } // Paper
diff --git a/src/main/java/net/minecraft/server/PlayerChunkMap.java b/src/main/java/net/minecraft/server/PlayerChunkMap.java
index 2c7ee012a7ae9ee8c269bb469282202f2a846ebf..51a19bce92c801912030699def8534213d77d310 100644
--- a/src/main/java/net/minecraft/server/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/PlayerChunkMap.java
@@ -1363,11 +1363,11 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
                     chunk.setLoaded(true);
                     this.world.a(chunk.getTileEntities().values());
                     List<Entity> list = null;
-                    List<Entity>[] aentityslice = chunk.getEntitySlices(); // Spigot
+                    EntitySlice<Entity>[] aentityslice = chunk.getAsSlices(); // Spigot // Yatopia - md_5 is stupid
                     int i = aentityslice.length;
 
                     for (int j = 0; j < i; ++j) {
-                        List<Entity> entityslice = aentityslice[j]; // Spigot
+                        EntitySlice<Entity> entityslice = aentityslice[j]; // Spigot // Yatopia - md_5 is stupid
                         Iterator iterator = entityslice.iterator();
 
                         while (iterator.hasNext()) {
@@ -1648,7 +1648,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
 
             // CraftBukkit - decompile error
             csvwriter.a(chunkcoordintpair.x, chunkcoordintpair.z, playerchunk.getTicketLevel(), optional.isPresent(), optional.map(IChunkAccess::getChunkStatus).orElse(null), optional1.map(Chunk::getState).orElse(null), a(playerchunk.c()), a(playerchunk.a()), a(playerchunk.b()), this.chunkDistanceManager.c(entry.getLongKey()), !this.isOutsideOfRange(chunkcoordintpair), optional1.map((chunk) -> {
-                return Stream.of(chunk.getEntitySlices()).mapToInt(List::size).sum(); // Spigot
+                return Stream.of(chunk.getAsSlices()).mapToInt(EntitySlice::size).sum(); // Spigot // Yatopia
             }).orElse(0), optional1.map((chunk) -> {
                 return chunk.getTileEntities().size();
             }).orElse(0));
diff --git a/src/main/java/net/minecraft/server/VoxelShape.java b/src/main/java/net/minecraft/server/VoxelShape.java
index 700660dd93b3090334bb3033d5f5fdd6ab684744..98f9ded42264cb88cff701a85d22d99e203ef7cf 100644
--- a/src/main/java/net/minecraft/server/VoxelShape.java
+++ b/src/main/java/net/minecraft/server/VoxelShape.java
@@ -78,7 +78,7 @@ public abstract class VoxelShape {
 
     public final List<AxisAlignedBB> getBoundingBoxesRepresentation() { return this.d(); } // Tuinity - OBFHELPER
     public List<AxisAlignedBB> d() {
-        List<AxisAlignedBB> list = Lists.newArrayList();
+        List<AxisAlignedBB> list = new net.yatopia.server.list.GlueList<>(); // Yatopia
 
         this.b((d0, d1, d2, d3, d4, d5) -> {
             list.add(new AxisAlignedBB(d0, d1, d2, d3, d4, d5));
diff --git a/src/main/java/net/minecraft/server/VoxelShapes.java b/src/main/java/net/minecraft/server/VoxelShapes.java
index db735e29d427cc8f4bd4ba54c7a44daf9fed9e61..877ef81bd8285167ce11c116b8ad803fda63c6c9 100644
--- a/src/main/java/net/minecraft/server/VoxelShapes.java
+++ b/src/main/java/net/minecraft/server/VoxelShapes.java
@@ -40,7 +40,9 @@ public final class VoxelShapes {
         if (shape instanceof com.tuinity.tuinity.voxel.AABBVoxelShape) {
             com.tuinity.tuinity.voxel.AABBVoxelShape shapeCasted = (com.tuinity.tuinity.voxel.AABBVoxelShape)shape;
             if (shapeCasted.aabb.voxelShapeIntersect(aabb)) {
+                if (!list.contains(shapeCasted.aabb)) { // Yatopia start - make sure it doesn't contain already
                 list.add(shapeCasted.aabb);
+                } // Yatopia end
             }
         } else if (shape instanceof VoxelShapeArray) {
             VoxelShapeArray shapeCasted = (VoxelShapeArray)shape;
@@ -54,14 +56,19 @@ public final class VoxelShapes {
                 double minX, minY, minZ, maxX, maxY, maxZ;
                 if (aabb.voxelShapeIntersect(minX = boundingBox.minX + offX, minY = boundingBox.minY + offY, minZ = boundingBox.minZ + offZ,
                         maxX = boundingBox.maxX + offX, maxY = boundingBox.maxY + offY, maxZ = boundingBox.maxZ + offZ)) {
-                    list.add(new AxisAlignedBB(minX, minY, minZ, maxX, maxY, maxZ, false));
+                    // Yatopia start - make sure it doesn't contain already
+                    AxisAlignedBB addedBox = new AxisAlignedBB(minX, minY, minZ, maxX, maxY, maxZ, false);
+                    if (!list.contains(addedBox)) {
+                        list.add(addedBox);
+                    }
+                    // Yatopia end
                 }
             }
         } else {
             java.util.List<AxisAlignedBB> boxes = shape.getBoundingBoxesRepresentation();
             for (int i = 0, len = boxes.size(); i < len; ++i) {
                 AxisAlignedBB box = boxes.get(i);
-                if (box.voxelShapeIntersect(aabb)) {
+                if (box.voxelShapeIntersect(aabb) && !list.contains(box)) { // Yatopia - make sure it doesn't contain already
                     list.add(box);
                 }
             }
diff --git a/src/main/java/net/minecraft/server/WorldServer.java b/src/main/java/net/minecraft/server/WorldServer.java
index 77cdfae804f9a3a5452dc70adc7da09d53f51998..e643043398756971571a6cba8237b74385ded898 100644
--- a/src/main/java/net/minecraft/server/WorldServer.java
+++ b/src/main/java/net/minecraft/server/WorldServer.java
@@ -787,8 +787,14 @@ public class WorldServer extends World implements GeneratorAccessSeed {
     }
 
     public final void getCollisions(@Nullable Entity entity, AxisAlignedBB axisalignedbb, List<AxisAlignedBB> list, boolean loadChunks) {
+        // Yatopia start - jellysquid is better
+        /*
         this.getCollisionsForBlocksOrWorldBorder(entity, axisalignedbb, list, loadChunks);
         this.getEntityHardCollisions(entity, axisalignedbb, null, list);
+         */
+        me.jellysquid.mods.lithium.common.entity.LithiumEntityCollisions.fillEntityCollisionsList(this, entity, list, axisalignedbb, loadChunks);
+        me.jellysquid.mods.lithium.common.entity.LithiumEntityCollisions.fillBlockCollisionsList(this, list, entity, axisalignedbb);
+        // Yatopia end
     }
 
     @Override
@@ -1871,12 +1877,12 @@ public class WorldServer extends World implements GeneratorAccessSeed {
         }
         // Spigot End
         this.tileEntityListUnload.addAll(chunk.getTileEntities().values());
-        List[] aentityslice = chunk.getEntitySlices(); // Spigot
+        EntitySlice<Entity>[] aentityslice = chunk.getAsSlices(); // Spigot // Yatopia - md_5 is stupid
         int i = aentityslice.length;
 
         java.util.List<Entity> toMoveChunks = new java.util.ArrayList<>(); // Paper
         for (int j = 0; j < i; ++j) {
-            List<Entity> entityslice = aentityslice[j]; // Spigot
+            EntitySlice<Entity> entityslice = aentityslice[j]; // Spigot // Yatopia - md_5 is stupid
             Iterator iterator = entityslice.iterator();
 
             while (iterator.hasNext()) {
diff --git a/src/main/java/net/yatopia/server/HoldingConsumer.java b/src/main/java/net/yatopia/server/HoldingConsumer.java
new file mode 100644
index 0000000000000000000000000000000000000000..44f39064fa52b8249887f83494b71699d653c4f8
--- /dev/null
+++ b/src/main/java/net/yatopia/server/HoldingConsumer.java
@@ -0,0 +1,17 @@
+package net.yatopia.server;
+
+import java.util.function.Consumer;
+
+public final class HoldingConsumer<T> implements Consumer<T> {
+
+    private T value;
+
+    @Override
+    public void accept(T t) {
+        this.value = t;
+    }
+
+    public T getValue() {
+        return value;
+    }
+}