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embeddedtembeddedt
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Implement a significantly more optimized biome lookup for surface rules
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‎src/main/java/org/embeddedt/modernfix/common/mixin/perf/optimize_surface_rules/BiomeManagerAccessor.java‎

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package org.embeddedt.modernfix.common.mixin.perf.optimize_surface_rules;
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import net.minecraft.world.level.biome.BiomeManager;
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import org.spongepowered.asm.mixin.Mixin;
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import org.spongepowered.asm.mixin.gen.Accessor;
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@Mixin(BiomeManager.class)
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public interface BiomeManagerAccessor {
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@Accessor("biomeZoomSeed")
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long mfix$getZoomSeed();
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@Accessor("noiseBiomeSource")
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BiomeManager.NoiseBiomeSource mfix$getBiomeSource();
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}

‎src/main/java/org/embeddedt/modernfix/common/mixin/perf/optimize_surface_rules/SurfaceSystemMixin.java‎

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package org.embeddedt.modernfix.common.mixin.perf.optimize_surface_rules;
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import com.llamalad7.mixinextras.sugar.Local;
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import net.minecraft.core.BlockPos;
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import net.minecraft.core.Holder;
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import net.minecraft.core.Registry;
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import net.minecraft.world.level.biome.Biome;
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import net.minecraft.world.level.biome.BiomeManager;
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import net.minecraft.world.level.chunk.ChunkAccess;
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import net.minecraft.world.level.levelgen.NoiseChunk;
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import net.minecraft.world.level.levelgen.RandomState;
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import net.minecraft.world.level.levelgen.SurfaceRules;
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import net.minecraft.world.level.levelgen.SurfaceSystem;
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import net.minecraft.world.level.levelgen.WorldGenerationContext;
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import org.embeddedt.modernfix.world.gen.ChunkBiomeLookup;
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import org.spongepowered.asm.mixin.Mixin;
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import org.spongepowered.asm.mixin.injection.At;
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import org.spongepowered.asm.mixin.injection.Inject;
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import org.spongepowered.asm.mixin.injection.ModifyArg;
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import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
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import java.util.function.Function;
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@Mixin(SurfaceSystem.class)
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public class SurfaceSystemMixin {
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private static final ThreadLocal<ChunkBiomeLookup> MFIX_LOOKUP_CACHE = ThreadLocal.withInitial(ChunkBiomeLookup::new);
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@ModifyArg(method = "buildSurface", at = @At(value = "INVOKE", target = "Lnet/minecraft/world/level/levelgen/SurfaceRules$Context;<init>(Lnet/minecraft/world/level/levelgen/SurfaceSystem;Lnet/minecraft/world/level/levelgen/RandomState;Lnet/minecraft/world/level/chunk/ChunkAccess;Lnet/minecraft/world/level/levelgen/NoiseChunk;Ljava/util/function/Function;Lnet/minecraft/core/Registry;Lnet/minecraft/world/level/levelgen/WorldGenerationContext;)V"), index = 4)
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private Function<BlockPos, Holder<Biome>> useFasterLookup(Function<BlockPos, Holder<Biome>> biomeGetter, @Local(ordinal = 0, argsOnly = true) BiomeManager manager, @Local(ordinal = 0, argsOnly = true) ChunkAccess chunk) {
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var lookup = MFIX_LOOKUP_CACHE.get();
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BiomeManagerAccessor accessor = (BiomeManagerAccessor)manager;
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lookup.prepare(accessor.mfix$getBiomeSource(), accessor.mfix$getZoomSeed(), chunk, manager);
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return lookup;
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}
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@Inject(method = "buildSurface", at = @At("RETURN"))
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private void disposeLookup(RandomState randomState, BiomeManager biomeManager, Registry<Biome> biomes, boolean p_224652_, WorldGenerationContext context, ChunkAccess chunk, NoiseChunk noiseChunk, SurfaceRules.RuleSource ruleSource, CallbackInfo ci) {
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MFIX_LOOKUP_CACHE.get().dispose();
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}
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}

‎src/main/java/org/embeddedt/modernfix/world/gen/ChunkBiomeLookup.java‎

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package org.embeddedt.modernfix.world.gen;
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import net.minecraft.core.BlockPos;
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import net.minecraft.core.Holder;
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import net.minecraft.core.QuartPos;
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import net.minecraft.util.LinearCongruentialGenerator;
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import net.minecraft.util.Mth;
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import net.minecraft.world.level.biome.Biome;
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import net.minecraft.world.level.biome.BiomeManager;
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import net.minecraft.world.level.chunk.ChunkAccess;
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import java.util.Arrays;
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import java.util.function.Function;
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/**
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* Drop-in replacement for {@code biomeManager::getBiome} in SurfaceSystem.buildSurface.
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*
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* <p>Pre-computes the Voronoi bias (fiddle) values and quart-resolution biome data for an
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* entire chunk, then uses two optimizations:
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* <ul>
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* <li><b>Uniform check:</b> If all 8 Voronoi candidate cells for a given quart position
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* hold the same biome, the Voronoi computation is skipped entirely.</li>
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* <li><b>Pre-computed bias:</b> When the Voronoi is needed, the 48 LCG operations per block
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* are replaced by array lookups of pre-computed fiddle values.</li>
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* </ul>
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*/
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public class ChunkBiomeLookup implements Function<BlockPos, Holder<Biome>> {
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@SuppressWarnings("unchecked")
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private Holder<Biome>[] biomes = new Holder[0];
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private double[] biasX = new double[0], biasY = new double[0], biasZ = new double[0];
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private boolean[] uniform = new boolean[0];
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private int qMinX, qMinY, qMinZ;
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private int sizeX, sizeY, sizeZ;
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private BiomeManager fallbackManager;
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/**
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* Pre-compute biome and bias data for the given chunk. Must be called before any
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* {@link #getBiome} calls for positions within this chunk.
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*
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* @param source the underlying quart-resolution biome source (e.g. the chunk)
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* @param biomeZoomSeed the obfuscated biome zoom seed from BiomeManager
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*/
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@SuppressWarnings("unchecked")
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public void prepare(BiomeManager.NoiseBiomeSource source, long biomeZoomSeed, ChunkAccess chunk, BiomeManager fallback) {
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int chunkMinX = chunk.getPos().getMinBlockX();
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int chunkMinZ = chunk.getPos().getMinBlockZ();
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int minBuildHeight = chunk.getMinBuildHeight();
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int maxBuildHeight = minBuildHeight + chunk.getHeight(); // exclusive
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// BiomeManager.getBiome subtracts a 2-block offset before converting to quart coords,
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// then considers quart and quart+1 as the 8 Voronoi candidates.
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int biomeOffset = 2;
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int minBlockX = chunkMinX - biomeOffset;
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int maxBlockX = chunkMinX + 15 - biomeOffset;
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int minBlockZ = chunkMinZ - biomeOffset;
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int maxBlockZ = chunkMinZ + 15 - biomeOffset;
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int minBlockY = minBuildHeight - biomeOffset;
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int maxBlockY = maxBuildHeight - 1 - biomeOffset;
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// Quart range: fromBlock(min) to fromBlock(max) + 1 (for the +1 Voronoi candidate)
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this.qMinX = QuartPos.fromBlock(minBlockX);
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int qMaxX = QuartPos.fromBlock(maxBlockX) + 1;
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this.qMinZ = QuartPos.fromBlock(minBlockZ);
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int qMaxZ = QuartPos.fromBlock(maxBlockZ) + 1;
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this.qMinY = QuartPos.fromBlock(minBlockY);
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int qMaxY = QuartPos.fromBlock(maxBlockY) + 1;
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this.sizeX = qMaxX - qMinX + 1; // always 6 for 16-wide chunks
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this.sizeY = qMaxY - qMinY + 1;
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this.sizeZ = qMaxZ - qMinZ + 1;
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int totalCells = sizeX * sizeY * sizeZ;
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// Reuse arrays across chunks if large enough
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if (biomes.length < totalCells) {
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biomes = new Holder[totalCells];
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biasX = new double[totalCells];
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biasY = new double[totalCells];
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biasZ = new double[totalCells];
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uniform = new boolean[totalCells];
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}
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// Fetch quart-resolution biomes
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boolean isSingleBiome = !fetchBiomes(source);
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if (isSingleBiome) {
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// All cells hold the same biome, so no need to do expensive computations.
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Arrays.fill(uniform, 0, totalCells, true);
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} else {
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this.computeUniformity();
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this.computeBiases(biomeZoomSeed);
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}
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this.fallbackManager = fallback;
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}
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public void dispose() {
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// Make sure we do not retain strong references to the biome holders
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Arrays.fill(biomes, null);
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}
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private boolean fetchBiomes(BiomeManager.NoiseBiomeSource source) {
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var biomes = this.biomes;
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Holder<Biome> firstSeen = null;
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boolean seenMultiple = false;
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for (int rx = 0; rx < sizeX; rx++) {
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int wx = qMinX + rx;
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for (int rz = 0; rz < sizeZ; rz++) {
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int wz = qMinZ + rz;
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for (int ry = 0; ry < sizeY; ry++) {
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int wy = qMinY + ry;
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var biome = source.getNoiseBiome(wx, wy, wz);
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biomes[index(rx, ry, rz)] = biome;
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if (biome != firstSeen) {
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if (firstSeen == null) {
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firstSeen = biome;
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} else {
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seenMultiple = true;
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}
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}
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}
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}
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}
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return seenMultiple;
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}
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private void computeUniformity() {
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// For each quart position, check if all 8 Voronoi candidates hold the same biome.
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// If so, the Voronoi result is guaranteed to be that biome regardless of fractional
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// position, so we can skip the distance computation entirely.
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var uniform = this.uniform;
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int sizeX = this.sizeX, sizeY = this.sizeY, sizeZ = this.sizeZ;
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for (int rx = 0; rx < sizeX - 1; rx++) {
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for (int rz = 0; rz < sizeZ - 1; rz++) {
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for (int ry = 0; ry < sizeY - 1; ry++) {
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uniform[index(rx, ry, rz)] = isUniform(rx, ry, rz);
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}
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}
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}
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}
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private void computeBiases(long biomeZoomSeed) {
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int sizeX = this.sizeX, sizeY = this.sizeY, sizeZ = this.sizeZ;
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int qMinX = this.qMinX, qMinY = this.qMinY, qMinZ = this.qMinZ;
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// Pre-compute bias (fiddle) values for the Voronoi distance computation.
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for (int rx = 0; rx < sizeX; rx++) {
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int wx = qMinX + rx;
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for (int rz = 0; rz < sizeZ; rz++) {
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int wz = qMinZ + rz;
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for (int ry = 0; ry < sizeY; ry++) {
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computeBias(index(rx, ry, rz), biomeZoomSeed, wx, qMinY + ry, wz);
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}
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}
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}
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}
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private void computeBias(int idx, long seed, int x, int y, int z) {
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// Reproduces the LCG chain from BiomeManager.getFiddledDistance exactly
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long s = LinearCongruentialGenerator.next(seed, x);
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s = LinearCongruentialGenerator.next(s, y);
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s = LinearCongruentialGenerator.next(s, z);
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s = LinearCongruentialGenerator.next(s, x);
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s = LinearCongruentialGenerator.next(s, y);
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s = LinearCongruentialGenerator.next(s, z);
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biasX[idx] = getFiddle(s);
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s = LinearCongruentialGenerator.next(s, seed);
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biasY[idx] = getFiddle(s);
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s = LinearCongruentialGenerator.next(s, seed);
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biasZ[idx] = getFiddle(s);
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}
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private static double getFiddle(long seed) {
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double d = (double) Math.floorMod(seed >> 24, 1024) / 1024.0D;
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return (d - 0.5D) * 0.9D;
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}
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private boolean isUniform(int rx, int ry, int rz) {
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var biomes = this.biomes;
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Holder<Biome> ref = biomes[index(rx, ry, rz)];
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for (int dx = 0; dx <= 1; dx++) {
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for (int dy = 0; dy <= 1; dy++) {
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for (int dz = 0; dz <= 1; dz++) {
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if (biomes[index(rx + dx, ry + dy, rz + dz)] != ref) {
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return false;
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}
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}
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}
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}
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return true;
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}
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private int index(int rx, int ry, int rz) {
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return (rx * sizeY + ry) * sizeZ + rz;
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}
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@Override
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public Holder<Biome> apply(BlockPos pos) {
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return getBiome(pos);
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}
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public Holder<Biome> getBiome(BlockPos pos) {
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int i = pos.getX() - 2;
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int j = pos.getY() - 2;
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int k = pos.getZ() - 2;
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int rx = QuartPos.fromBlock(i) - qMinX;
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int ry = QuartPos.fromBlock(j) - qMinY;
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int rz = QuartPos.fromBlock(k) - qMinZ;
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if (rx < 0 || rx >= sizeX - 1 || ry < 0 || ry >= sizeY - 1 || rz < 0 || rz >= sizeZ - 1) {
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return fallbackManager.getBiome(pos);
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}
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int baseIdx = index(rx, ry, rz);
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if (uniform[baseIdx]) {
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return biomes[baseIdx];
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}
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return getBiomeWithVoronoi(i, j, k, rx, ry, rz);
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}
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private Holder<Biome> getBiomeWithVoronoi(int i, int j, int k, int rx, int ry, int rz) {
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var biasX = this.biasX;
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var biasY = this.biasY;
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var biasZ = this.biasZ;
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double d0 = (double) QuartPos.quartLocal(i) / 4.0D;
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double d1 = (double) QuartPos.quartLocal(j) / 4.0D;
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double d2 = (double) QuartPos.quartLocal(k) / 4.0D;
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int closestIdx = 0;
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double closestDist = Double.POSITIVE_INFINITY;
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for (int c = 0; c < 8; c++) {
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boolean fx = (c & 4) == 0;
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boolean fy = (c & 2) == 0;
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boolean fz = (c & 1) == 0;
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int idx = index(
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rx + (fx ? 0 : 1),
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ry + (fy ? 0 : 1),
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rz + (fz ? 0 : 1)
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);
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double dx = (fx ? d0 : d0 - 1.0D) + biasX[idx];
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double dy = (fy ? d1 : d1 - 1.0D) + biasY[idx];
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double dz = (fz ? d2 : d2 - 1.0D) + biasZ[idx];
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double dist = Mth.square(dx) + Mth.square(dy) + Mth.square(dz);
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if (dist < closestDist) {
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closestDist = dist;
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closestIdx = idx;
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}
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}
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return biomes[closestIdx];
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}
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}

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