A face is a single Non-uniform Rational B-Spline (NURBS) and is the smallest area entity. It has a separate underlying mathematical definition, specified when it was created.

All faces are represented mathematically with the following formulations:
  • plane
  • cylinder/cone
  • sphere
  • torus

A surface can be made up of a single face type or of multiple face types. Multiple types are used for more complex surfaces that contain sharp corners or highly complex shapes.