It still has that. Just the index type is different. It also makes it easier to iterate over the whole thing.The differences from the grid used in EMBed are: - The voxel index is actually a triple if ints. This makes computing a point in a voxel fast without the large tables used in EMBed. I think this is the right choice speed wise, but we can always test (and it is trivial to change).The reason we had it as single array in EMBed is for consistency with external programs like fttw, EMAN. I think that we should keep it like that.