Convert a subdivision surface into an equivalent polysurface made from NURBS faces.

Input parameters:

1. Sd → Subdivision surface to convert.
2. Pk → When true, the NURBS patches will be packed.
   •  True → Pack
   • False → Unpack
3. Vx → Continuity handling at extraordinary vertices.
   • 0 → None
   • 1 → G1 Worst
   • 2 → G2
   • 3 → G1 Middle
   • 4 → G1 Best

Output parameters:

1. Nr → Polysurface made up from NURBS patches.