Fix race issue with vanilla gen. Improve mem usage a bit

fabric/src/main/java/com/seibel/lod/fabric/mixins/MixinChunkGenerator.java

@@ -0,0 +1,46 @@
+package com.seibel.lod.fabric.mixins;
+
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Overwrite;
+import org.spongepowered.asm.mixin.Shadow;
+
+import net.minecraft.CrashReport;
+import net.minecraft.ReportedException;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.WorldGenRegion;
+import net.minecraft.world.level.StructureFeatureManager;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeSource;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.WorldgenRandom;
+
+@Mixin(ChunkGenerator.class)
+public class MixinChunkGenerator {
+	@Shadow
+	@Final
+	protected BiomeSource biomeSource;
+	
+	@Overwrite
+    public void applyBiomeDecoration(WorldGenRegion worldGenRegion, StructureFeatureManager structureFeatureManager) {
+        int i = worldGenRegion.getCenterX();
+        int j = worldGenRegion.getCenterZ();
+        int k = i * 16;
+        int l = j * 16;
+        BlockPos blockPos = new BlockPos(k, 0, l);
+        Biome biome = this.biomeSource.getNoiseBiome((i << 2) + 2, 2, (j << 2) + 2);
+        WorldgenRandom worldgenRandom = new WorldgenRandom();
+        long m = worldgenRandom.setDecorationSeed(worldGenRegion.getSeed(), k, l);
+        try {
+			synchronized(this) {
+				biome.generate(structureFeatureManager, (ChunkGenerator)(Object)this, worldGenRegion, m, worldgenRandom, blockPos);
+			}
+        }
+        catch (Exception exception) {
+            CrashReport crashReport = CrashReport.forThrowable(exception, "Biome decoration");
+            crashReport.addCategory("Generation").setDetail("CenterX", i).setDetail("CenterZ", j).setDetail("Seed", m).setDetail("Biome", biome);
+            throw new ReportedException(crashReport);
+        }
+    }
+
+}

fabric/src/main/resources/fabric.lod.mixins.json

@@ -5,7 +5,8 @@
   "compatibilityLevel": "JAVA_8",
   "mixins": [
     "events.MixinServerLevel",
-    "unsafe.MixinPalettedContainer"
+    "unsafe.MixinPalettedContainer",
+    "MixinChunkGenerator"
   ],
   "client": [
     "MixinMinecraft",