From d407c928958ff7c65ac1277c325f0c4d987ba709 Mon Sep 17 00:00:00 2001
From: Steveplays28 <djspaargaren@outlook.com>
Date: Sun, 12 Nov 2023 16:08:29 +0100
Subject: [PATCH] feat: Add micro-opimisation for populating biomes in chunk
 sections

This optimisations swaps the order of the Y and Z axis `fori` loops. This is taken from [Rho](https://github.com/jaskarth/rho/blob/main/src/main/java/supercoder79/rho/mixin/MixinNoiseChunkGenerator.java).
---
 .../noisium/mixin/ChunkSectionMixin.java      | 41 +++++++++++++++++++
 src/main/resources/noisium.mixins.json        |  1 +
 2 files changed, 42 insertions(+)
 create mode 100644 src/main/java/io/github/steveplays28/noisium/mixin/ChunkSectionMixin.java

diff --git a/src/main/java/io/github/steveplays28/noisium/mixin/ChunkSectionMixin.java b/src/main/java/io/github/steveplays28/noisium/mixin/ChunkSectionMixin.java
new file mode 100644
index 0000000..c41e37e
--- /dev/null
+++ b/src/main/java/io/github/steveplays28/noisium/mixin/ChunkSectionMixin.java
@@ -0,0 +1,41 @@
+package io.github.steveplays28.noisium.mixin;
+
+import net.minecraft.registry.entry.RegistryEntry;
+import net.minecraft.world.biome.Biome;
+import net.minecraft.world.biome.source.BiomeSupplier;
+import net.minecraft.world.biome.source.util.MultiNoiseUtil;
+import net.minecraft.world.chunk.ChunkSection;
+import net.minecraft.world.chunk.PalettedContainer;
+import net.minecraft.world.chunk.ReadableContainer;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Overwrite;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.Unique;
+
+@Mixin(ChunkSection.class)
+public class ChunkSectionMixin {
+	@Unique
+	private static final int sliceSize = 4;
+
+	@Shadow
+	private ReadableContainer<RegistryEntry<Biome>> biomeContainer;
+
+	/**
+	 * @author Steveplays28
+	 * @reason Axis order micro-optimisation
+	 */
+	@Overwrite
+	public void populateBiomes(BiomeSupplier biomeSupplier, MultiNoiseUtil.MultiNoiseSampler sampler, int x, int y, int z) {
+		PalettedContainer<RegistryEntry<Biome>> palettedContainer = this.biomeContainer.slice();
+
+		for (int posX = 0; posX < sliceSize; ++posX) {
+			for (int posZ = 0; posZ < sliceSize; ++posZ) {
+				for (int posY = 0; posY < sliceSize; ++posY) {
+					palettedContainer.swapUnsafe(posX, posY, posZ, biomeSupplier.getBiome(x + posX, y + posY, z + posZ, sampler));
+				}
+			}
+		}
+
+		this.biomeContainer = palettedContainer;
+	}
+}
diff --git a/src/main/resources/noisium.mixins.json b/src/main/resources/noisium.mixins.json
index be96a35..a72cad8 100644
--- a/src/main/resources/noisium.mixins.json
+++ b/src/main/resources/noisium.mixins.json
@@ -5,6 +5,7 @@
   "compatibilityLevel": "JAVA_17",
   "mixins": [
     "ChainedBlockSourceMixin",
+    "ChunkSectionMixin",
     "NoiseChunkGeneratorMixin"
   ],
   "client": [