The Relationship Between RATS-splines and the Catmull and Clark B-splines

Abstract

This paper presents the relationship between the Recursive Arbitrary Topology Splines (RATS) method, derived by the authors, and the Catmull and Clark recursive B-Spline method. Both methods are capable of defining surfaces of any arbitrary topology of control points. They "fill-in" n-sided regions with four-sided patches. The Catmull & Clark method is derived from the midpoint subdivision of B-splines whereas the RATS method is derived from the midpoint subdivision of Bézier splines. RATS generates an additional set of patches defining the border of the surface but the RATS inner surface is identical to the Catmull and Clark surface. This paper illustrates this relationship between the two methods.