For NURBS objects in the scene, 3ds Max uses a different internal representation of NURBS objects than the MAXScript and SDK classes do. These MAXScript and SDK classes are simply a means to access these internal 3ds Max NURBS objects and allow them to be manipulated.
The object used in communication between the internal 3ds Max NURBS objects and the classes in MAXScript available to work with these objects is the NURBSSet. There are also two functions used in this communication. The first is the constructor NURBSNode() and the second is a node method, getNURBSSet() . How these are used is described in the following topics:
Modifying Existing NURBS Objects
Parameter Ranges for Curves and Surfaces
Materials Assignment and Texture Coordinates