The Convert to NURBS command converts planar objects and 3D polygons into NURBS curves, and converts the faces of solids to NURBS surfaces. This is a quick way of creating NURBS curves from circles and arcs, or NURBS surfaces from an extrusion, sweep, or other solid.
To convert to NURBS curves or surfaces:
Select the object or solid to convert to NURBS surfaces.
Select Modify > Convert > Convert to NURBS.
The selection is converted to a NURBS surface or a NURBS curve, as reflected in the Object Info palette.
If the solid consisted of several faces, the conversion results in a group of NURBS surfaces. Select Modify > Ungroup to access the individual NURBS surfaces that make up the solid.
~~~~~~~~~~~~~~~~~~~~~~~~~