Microsoft KB Archive/163046

= Microsoft Knowledge Base =

What are C0, C1, and C2 Continuity For NURBS Curves?
Last reviewed: February 3, 1997

Article ID: Q163046

The information in this article applies to:


 * Softimage 3D for IRIX, versions 3.5, 3.51
 * Softimage 3D for Windows NT, versions 3.01, 3.51

SUMMARY
The Effect -> Subdivision command in the Model module allows you to subdivide polygons of a polygon mesh object or subdivide a NURBS curve or surface. When you select a NURBS curve or surface, you can choose spots on the curve or surface at which to subdivide. When you subdivide a NURBS curve, you are inserting new points on the curve.

Using the Continuity parameter (describes how smooth you want the curve), you can specify the degree of continuity that is applied to these points. For a cubic curve inserting 1 knot means C2 continuity, which produces the most smoothness to the curve. In contrast, C0 inserts a triple knot (same knot value repeated three times). In this case you would have a new control point directly on the curve and the curve being discontinuous at that point (at that point, you can make a sharp angle). Continuity is always related to the degree of the curve.