BiomePlugin.java

package com.thevoxelbox.biome;

import org.spongepowered.api.Game;
import org.spongepowered.api.data.DataContainer;
import org.spongepowered.api.data.MemoryDataContainer;
import org.spongepowered.api.event.Listener;
import org.spongepowered.api.event.game.state.GameInitializationEvent;
import org.spongepowered.api.event.game.state.GamePostInitializationEvent;
import org.spongepowered.api.event.world.LoadWorldEvent;
import org.spongepowered.api.plugin.Plugin;
import org.spongepowered.api.plugin.PluginContainer;
import org.spongepowered.api.world.World;
import org.spongepowered.api.world.WorldCreationSettings;
import org.spongepowered.api.world.biome.BiomeType;
import org.spongepowered.api.world.biome.BiomeTypes;
import org.spongepowered.api.world.extent.MutableBiomeArea;
import org.spongepowered.api.world.gen.BiomeGenerator;
import org.spongepowered.api.world.gen.WorldGenerator;
import org.spongepowered.api.world.gen.WorldGeneratorModifier;

import com.flowpowered.math.vector.Vector2i;
import com.google.inject.Inject;

@Plugin(id = "biome-plugin", name = "Biome Plugin")
public class BiomePlugin implements WorldGeneratorModifier {

    public static BiomePlugin instance;
    
    private BiomeType[] biomes;

    @Inject private PluginContainer plugin;

    public BiomePlugin() {

    }

    @Listener
    public void onInitialize(GamePostInitializationEvent event) {
        instance = this;
        Game game = event.getGame();

        game.getRegistry().registerWorldGeneratorModifier(this);
        this.biomes = game.getRegistry().getAllOf(BiomeType.class).toArray(new BiomeType[0]);
//        System.out.println("Found " + this.biomes.length + " biomes");
    }

//    @Listener
    public void onWorldLoad(LoadWorldEvent event) {
        World world = event.getTargetWorld();
        System.out.println("World load: " + world.getName() + " " + world.getDimension().getType().getName());
        System.out.println("Applying world gen modifier");
        WorldGenerator gen = world.getWorldGenerator();
        modifyWorldGenerator(world.getCreationSettings(), new MemoryDataContainer(), gen);
        world.setWorldGenerator(gen);
        
    }

    @Override
    public String getName() {
        return plugin.getName();
    }

    @Override
    public void modifyWorldGenerator(WorldCreationSettings world, DataContainer settings, WorldGenerator worldGenerator) {
        worldGenerator.setBiomeGenerator(new TestBiomeGenerator(this.biomes));
    }

    @Override
    public String getId() {
        return plugin.getId();
    }

}

TestBiomeGenerator.java

package com.thevoxelbox.biome;

import org.spongepowered.api.world.biome.BiomeType;
import org.spongepowered.api.world.biome.BiomeTypes;
import org.spongepowered.api.world.extent.MutableBiomeArea;
import org.spongepowered.api.world.gen.BiomeGenerator;

import com.flowpowered.math.vector.Vector2i;

public class TestBiomeGenerator implements BiomeGenerator {

    private static final int BIOME_SIZE = 2;
    private final BiomeType[] biomes;

    public TestBiomeGenerator(BiomeType[] b) {
        this.biomes = new BiomeType[64];
        for (int i = 0; i < 64; i++) {
            if (i < b.length) {
//            	System.out.println(i + " " + b[i]);
                this.biomes[i] = b[i];
            } else {
                this.biomes[i] = BiomeTypes.OCEAN;
            }
        }
    }

    @Override
    public void generateBiomes(MutableBiomeArea buffer) {
        Vector2i min = buffer.getBiomeMin().div(64);
        int index = getIndex(min.getX(), min.getY());
        flood(buffer, this.biomes[index]);
//        System.err.println("Flooding " + min.getX() + " " + min.getY() + " with "  + this.biomes[index].getName());
    }

    private int getIndex(int x, int y) {
        x = (x / BIOME_SIZE) % 8;
        y = (y / BIOME_SIZE) % 8;
        if(x < 0) x += 8;
        if(y < 0) y += 8;
        return x + y * 8;
    }

    private void flood(MutableBiomeArea b, BiomeType type) {
        for (int x = 0; x < b.getBiomeSize().getX(); x++) {
            for (int y = 0; y < b.getBiomeSize().getY(); y++) {
                b.setBiome(x + b.getBiomeMin().getX(), y + b.getBiomeMin().getY(), type);
            }
        }
    }

}