Hi Jean-Francois, You can still enter a negative voxel size along one axis in the volume dialog Coordinates panel. Although the voxel size field will show just one number if all 3 axes have the same voxel size, you can enter 3 numbers separated by spaces, for example, 2.52 2.52 -2.52. I noticed that surfaces are dark if you do this. If you turn off the "two-sided lighting" option in the volume dialog under surface and mesh options the lighting will be bright again. I believe this undesirable effect is caused by the traversal of the 3 vertices of a surface triangle switching from counterclockwise to clockwise relative to the surface normal. Thanks for pointing out this trick for flipping map handedness. I wanted to do this a few days ago and didn't know how, even though I wrote the code. Tom