Modeling with subdivision surfaces has been the subject of investigation by
many researchers. To model most real-world objects, these subdivision sche
mes should have the ability to represent both sharp edges and vertices. In
this paper we propose a new method for edge and vertex insertion on four-di
rectional CI quadratic box spline surfaces. Edges and vertices may be inser
ted into an existing smooth surface and then deformed to have tangent plane
discontinuities. The approach is easy to implement and can be generalized
to work on other classes of subdivision schemes. (C) 1999 Elsevier Science
B.V. All rights reserved.