And in ViaCAD I am seeing some operations that end up using the NURBS surface, offsetting does seem to do it - if I take the nice looking N-sided patch by itself and thicken it into a solid with a thickness of 10 units, those same bumpy areas appear in the offset surface (here converted into a dense mesh):



So it seems that sometimes you get things calculated off of the ideal logical blend surface, and other times stuff happens on the approximated NURBS surface that's along with it.

- Michael