Yatopia/patches/server/0025-lithium-MixinChunkGeneratorAbstract.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: JellySquid <jellysquid+atwork@protonmail.com>
Date: Tue, 4 Aug 2020 21:06:02 +0200
Subject: [PATCH] lithium-MixinChunkGeneratorAbstract

Original code by JellySquid, licensed under GNU Lesser General Public License v3.0
you can find the original code on https://github.com/jellysquid3/lithium-fabric/tree/1.16.x/fabric (Yarn mappings)

Co-authored-by: tr7zw <tr7zw@live.de>

diff --git a/src/main/java/me/jellysquid/mods/lithium/common/world/noise/SimplexNoiseCache.java b/src/main/java/me/jellysquid/mods/lithium/common/world/noise/SimplexNoiseCache.java
new file mode 100644
index 0000000000000000000000000000000000000000..e6cd19e75a88f4dbf38d3cc63883068d95aa67d4
--- /dev/null
+++ b/src/main/java/me/jellysquid/mods/lithium/common/world/noise/SimplexNoiseCache.java
@@ -0,0 +1,135 @@
+package me.jellysquid.mods.lithium.common.world.noise;
+
+import it.unimi.dsi.fastutil.HashCommon;
+
+import net.minecraft.server.ChunkCoordIntPair;
+import net.minecraft.server.MathHelper;
+import net.minecraft.server.NoiseGenerator3Handler;
+
+import java.util.Arrays;
+
+/**
+ * A cache for the End's noise generator that caches computed values. Through the caching, we can eliminate a large
+ * amount of overhead in computing the noise values several hundred thousand times per chunk. This code uses the same
+ * array backed lossy cache as FastCachingLayerSampler.
+ */
+public class SimplexNoiseCache {
+    private static final int GRID_SIZE = 2;
+    private static final float MIN = -100.0F;
+    private static final float MAX = 80.0F;
+    private static final float ISLAND_RADIUS = 100.0F;
+    // The smallest encompassing power of two that can store all of the noise values in a chunk.
+    private static final int CACHE_SIZE = 8192;
+
+    private final int mask;
+    private final long[] keys;
+    private final float[] values;
+
+    private final NoiseGenerator3Handler sampler;
+
+    public SimplexNoiseCache(NoiseGenerator3Handler sampler) {
+        this.sampler = sampler;
+
+        this.mask = CACHE_SIZE - 1;
+
+        // Initialize default values
+        this.keys = new long[CACHE_SIZE];
+        Arrays.fill(this.keys, Long.MIN_VALUE);
+        this.values = new float[CACHE_SIZE];
+    }
+
+    /**
+     * Attempt to get the cached distance factor, saving computation time.
+     */
+    private float getDistanceFactor(int x, int z) {
+        // Hash key and get index
+        long key = ChunkCoordIntPair.pair(x, z);
+        int idx = (int) HashCommon.mix(key) & this.mask;
+
+        if (this.keys[idx] == key) {
+            // Cache hit, return cached value
+            return this.values[idx];
+        }
+
+        // Cache miss, compute and store value
+
+        // A marker for no value.
+        float value = -1.0F;
+
+        long lx = x;
+        long lz = z;
+        long distanceFromOriginSq = lx * lx +  lz * lz;
+
+        // Ensure we are 64 grid cells away from the origin.
+        if (distanceFromOriginSq > 64 * 64) {
+            // Reduce the number of island-forming grid cells by sampling noise with a threshold
+            if (this.sampler.a(x, z) < -0.9) {
+                // Generate a pseudo-random value from 9 to 21
+                value = (Math.abs(x) * 3439.0F +  Math.abs(z) * 147.0F) %13.0F +  9.0F;
+            }
+        }
+
+        // Store values in cache
+        this.keys[idx] = key;
+        this.values[idx] = value;
+
+        return value;
+    }
+
+    /**
+     * Mapped and cleaned up implementation of the End biome source's sampler. Tries to use cached values wherever
+     * possible.
+     */
+    public float getNoiseAt(int x, int z) {
+        // [VanillaCopy] TheEndBiomeSource#getNoiseAt
+
+        int gridX = x / GRID_SIZE;
+        int gridZ = z / GRID_SIZE;
+
+        // This is the "center point", offset to center around the current grid cell
+        int gridOriginX = x % GRID_SIZE;
+        int gridOriginZ = z % GRID_SIZE;
+
+        // Initialize density for the central island
+        float density = ISLAND_RADIUS - MathHelper.sqrt(x * x +  z * z) * 8.0F;
+        if (density >= MAX) {
+            return MAX;
+        }
+
+        // Iterate through 25x25 grid cells
+        for (int offsetX = -12; offsetX <= 12; offsetX++) {
+            for (int offsetZ = -12; offsetZ <= 12; offsetZ++) {
+                int globalGridX = gridX +  offsetX;
+                int globalGridZ = gridZ +  offsetZ;
+
+                // Try to retrieve values from cache
+                float distanceFactor = getDistanceFactor(globalGridX, globalGridZ);
+                if (distanceFactor != -1.0F) {
+                    // Compute the distance to the origin
+                    float deltaX = gridOriginX - offsetX * GRID_SIZE;
+                    float deltaZ = gridOriginZ - offsetZ * GRID_SIZE;
+
+                    // Calculate the density at this grid cell
+                    float scaledDistance = MathHelper.sqrt(deltaX * deltaX +  deltaZ * deltaZ) * distanceFactor;
+                    float densityHere = ISLAND_RADIUS - scaledDistance;
+
+                    // Try to return early if we're over the max
+                    if (densityHere > density) {
+                        if (densityHere >= MAX) {
+                            return MAX;
+                        }
+
+                        density = densityHere;
+                    }
+                }
+            }
+        }
+
+        // Avoid a call to Math.max because the density cannot be bigger than the max.
+        if (density < MIN) {
+            return MIN;
+        }
+
+        return density;
+    }
+}
diff --git a/src/main/java/net/minecraft/server/ChunkGeneratorAbstract.java b/src/main/java/net/minecraft/server/ChunkGeneratorAbstract.java
index 321ebe8891defb46f3ad3dfea37c9bb6e2025ad7..119804e5c12aca3f4fbfeaf424f46152f43b3941 100644
--- a/src/main/java/net/minecraft/server/ChunkGeneratorAbstract.java
+++ b/src/main/java/net/minecraft/server/ChunkGeneratorAbstract.java
@@ -57,12 +57,13 @@ public final class ChunkGeneratorAbstract extends ChunkGenerator {
     private final NoiseGenerator t;
     private final NoiseGeneratorOctaves u;
     @Nullable
-    private final NoiseGenerator3Handler v;
+    private final NoiseGenerator3Handler v; // Yatopia - yarn "SimplexNoiseSampler"
     protected final IBlockData f;
     protected final IBlockData g;
     private final long w;
     protected final Supplier<GeneratorSettingBase> h;
     private final int x;
+    private ThreadLocal<me.jellysquid.mods.lithium.common.world.noise.SimplexNoiseCache> tlCache; // Yatopia
 
     public ChunkGeneratorAbstract(WorldChunkManager worldchunkmanager, long i, Supplier<GeneratorSettingBase> supplier) {
         this(worldchunkmanager, worldchunkmanager, i, supplier);
@@ -99,7 +100,7 @@ public final class ChunkGeneratorAbstract extends ChunkGenerator {
         } else {
             this.v = null;
         }
-
+        this.tlCache = ThreadLocal.withInitial(() -> new me.jellysquid.mods.lithium.common.world.noise.SimplexNoiseCache(v)); // Yatopia
     }
 
     @Override
@@ -164,7 +165,8 @@ public final class ChunkGeneratorAbstract extends ChunkGenerator {
         double d3;
 
         if (this.v != null) {
-            d0 = (double) (WorldChunkManagerTheEnd.a(this.v, i, j) - 8.0F);
+            //d0 = (double) (WorldChunkManagerTheEnd.a(this.v, i, j) - 8.0F); // Yatopia
+            d0 = tlCache.get().getNoiseAt(i, j) - 8.0F; // Yatopia
             if (d0 > 0.0D) {
                 d1 = 0.25D;
             } else {