synchronized void setChunkOpDone(int x, int z, int op)
    {
        chunks[x][z].opsDone[op] = true;

        for (int xx = x - 2; xx <= x + 2; xx++)
            for (int zz = z - 2; zz <= z + 2; zz++)
                if (canDoOpToChunk(xx, zz, op + 1))
                    scheduleChunkForOp(xx, zz, op + 1);
    }