Offset surfaces

An offset of a polynomial or spline surface is rarely a member of that class, unless it is a pythagorean polynomial.

Such surfaces should be of great interest to the CAD/CAM/CAE Robotics, etc community. What can you say about the possibility that I can define, say, a NURBS surface, plus an offset value, say for a cutter radius, and then display not the “base” NURBS surface, but rather its “cutter offset”. I’m not sure that this is
the same concept that the glPolygonOffset function uses.

If I can do this with current OGL functions, please straighten me out. Otherwise, I would like to know what future plans or contradictions to design philosophy are involved here.