Hi Tony, Thanks for the fast reply! I see that feature now. That is fairly close and quite workable. I had used fill voids before however i wanted tighter control so that only certain voids were filled and not others. It would still be nice to be able to do this interactively by plane but for the meantime this does what I need. Think it was a case of not knowing the right key word to search for as i was using Solidworks type language to define it. Per chance, would you know how to apply this hide voxel to multiple volumes at once (so they share a exact common plane?