The degree of a NURBS determines its continuity or smoothness. In Softimage, NURBS can have one of two degrees:
Linear: straight segments joined at the control points. Linear NURBS have positional continuity (also known as C0, degree 0, or zero-order continuity); this means that although it is connected, it is not necessarily smooth. At least two control points are required to define a linear curve.
Cubic: smooth NURBS that are interpolated between the control points. Cubic NURBS have curvature continuity (also known as C2, degree 2, or second-order continuity); this means that there are no abrupt changes in the position, tangent, or curvature — in other words, it is very smooth. At least four control points are required to define a cubic curve.
Like curves, surfaces can be either cubic or linear. In addition, they can have different degrees in their U and V directions, so that they can be smooth in one direction and jagged in the other.
You can convert between cubic and linear by fitting — see Fitting Curves onto Curves and Fitting Surfaces.
In addition to linear and cubic, Softimage supports NURBS of other degrees imported from other programs.
