Displacing points increases active voxel count

[medakk]

I am initializing a OpenVDB level set from another data structure, something like:

while(...) {
    idx = GetNextIndex();
    pixel = GetNextPixel();
    coord = openvdb::Coord(idx[0], idx[1], idx[2]);
    vdbAccessor.setValue(coord, pixels);
}

The number of active voxels are 10498. If I displace all the indices by a constant amount(basically I have to translate them according to an origin), the number of active voxels becomes 12117. This translates to increase memory usage. What's causing this?

(my fundamental problem is that that original data has a concept of an "origin" and "spacing" between voxels, and I'm trying to recreate that in an OpenVDB grid)