public Cube(Chunk column, int cubeY, CubePrimer primer) {
        this(column, cubeY);

        int miny = cubeToMinBlock(cubeY);
        IHeightMap opindex = ((IColumn) column).getOpacityIndex();

        for (int x = 0; x < Cube.SIZE; x++) {
            for (int z = 0; z < Cube.SIZE; z++) {

                for (int y = Cube.SIZE - 1; y >= 0; y--) {
                    IBlockState newstate = primer.getBlockState(x, y, z);

                    if (newstate.getMaterial() != Material.AIR) {
                        if (storage == NULL_STORAGE) {
                            newStorage();
                        }
                        storage.set(x, y, z, newstate);

                        //int opacity = newstate.getLightOpacity();
                        //if (false || opacity != 0) {
                        //    column.setModified(true); //TODO: this is a bit of am abstraction leak... maybe ServerHeightMap needs its own isModified
                        //    opindex.onOpacityChange(x, miny | y, z, opacity);
                        //}
                    }
                }
            }
        }
        isSurfaceTracked = true;
        isModified = true;
    }

    private void newStorage() {
        storage = new ExtendedBlockStorage(cubeToMinBlock(getY()), world.provider.hasSkyLight());
    }

CubePrimer:

public class CubePrimer {
    public static final IBlockState DEFAULT_STATE = Blocks.AIR.getDefaultState();

    private final char[] data = new char[4096];

    public IBlockState getBlockState(int x, int y, int z) {
        @SuppressWarnings("deprecation")
        IBlockState iblockstate = Block.BLOCK_STATE_IDS.getByValue(this.data[getBlockIndex(x, y, z)]);
        return iblockstate == null ? DEFAULT_STATE : iblockstate;
    }

    public void setBlockState(int x, int y, int z, @Nonnull IBlockState state) {
        @SuppressWarnings("deprecation")
        char value = (char) Block.BLOCK_STATE_IDS.get(state);
        this.data[getBlockIndex(x, y, z)] = value;
    }

    private static int getBlockIndex(int x, int y, int z) {
        return x << 8 | z << 4 | y;
    }
}