Hello, I have a mod and I have a biome with a structure spawning in it but when it generates it sometimes is just fine but sometimes also spawns with a lot missing, my code:

public class WorldGenSimpleHouse extends WorldGenerator {

private static final BlockStateMatcher IS_GRASS = BlockStateMatcher.forBlock(Blocks.GRASS);
private final ResourceLocation HOUSE = new ResourceLocation(Reference.MODID + ":house");

public boolean generate(World worldIn, Random rand, BlockPos position) {
	while (worldIn.isAirBlock(position) && position.getY() > 2) {
		position = position.down();
	}
	if (!IS_GRASS.apply(worldIn.getBlockState(position))) {
		return false;
	}
        Random random = worldIn.getChunkFromChunkCoords(position.getX(), position.getZ()).getRandomWithSeed(987234911L);
        Rotation[] arotation = Rotation.values();
        Rotation rotation = arotation[random.nextInt(arotation.length)];
        ChunkPos chunkpos = new ChunkPos(position);
        StructureBoundingBox structureboundingbox = new StructureBoundingBox(chunkpos.getXStart(), 0, chunkpos.getZStart(), chunkpos.getXEnd(), 256, chunkpos.getZEnd());
        PlacementSettings placementsettings = (new PlacementSettings()).setRotation(rotation).setBoundingBox(structureboundingbox).func_189950_a(random);
        MinecraftServer minecraftserver = worldIn.getMinecraftServer();
	TemplateManager templatemanager = worldIn.getSaveHandler().getStructureTemplateManager();
        Template template = templatemanager.getTemplate(minecraftserver, HOUSE);
        template.func_189962_a(worldIn, position, placementsettings, 2);
	return true;
}

}

And my decorate method in my biome class

public void decorate(World worldIn, Random rand, BlockPos pos) {
	double d0 = GRASS_COLOR_NOISE.getValue((double) (pos.getX() +  / 200.0D, (double) (pos.getZ() +  / 200.0D);
	final WorldGenSimpleHouse HOUSE_GENERATOR = new WorldGenSimpleHouse();

	if (rand.nextInt(1500) == 0) {
		int i = rand.nextInt(16) + 8;
            int j = rand.nextInt(16) + 8;
            BlockPos blockpos = worldIn.getHeight(pos.add(i, 0, j)).up();
            HOUSE_GENERATOR.generate(worldIn, rand, blockpos);
		System.out.println("House generated at: X" + blockpos.getX() + ", Z" + blockpos.getZ());
	}
	this.theBiomeDecorator.flowersPerChunk = 4;
	this.theBiomeDecorator.grassPerChunk = 10;
	DOUBLE_PLANT_GENERATOR.setPlantType(BlockDoublePlant.EnumPlantType.GRASS);

	for (int i = 0; i < 7; ++i) {
		int j = rand.nextInt(16) + 8;
		int k = rand.nextInt(16) + 8;
		int l = rand.nextInt(worldIn.getHeight(pos.add(j, 0, k)).getY() + 32);
		DOUBLE_PLANT_GENERATOR.generate(worldIn, rand, pos.add(j, l, k));
	}

	super.decorate(worldIn, rand, pos);
}

You are setting you structure bounds to the size of the chunk, but your rotation is random. So your structure can generate partially outside of the chunk and outside the bounds.

I now have this, will it work? StructureBoundingBox structureboundingbox = new StructureBoundingBox(chunkpos.getXStart() - 16, 0, chunkpos.getZStart() - 16, chunkpos.getXEnd() + 16, 256, chunkpos.getZEnd() + 16);

I wouldn't know, why don't you test it? But I hazard to guess that the success will depend on the size of your structure.

It works, THANKS!!!