A Method for Analysis of C1-Continuity of Subdivision Surfaces

Denis Zorin

NYU Media Research Laboratory


A sufficient condition for C1-continuity of subdivision surfaces was proposed by Reif and extended to a more general setting in our previous work. In both cases, the analysis of C1-continuity is reduced to establishing injectivity and regularity of a characteristic map. In all known proofs of C1-continuity, explicit representation of the limit surface on an annular region was used to establish regularity, and a variety of relatively complex techniques were used to establish injectivity. We propose a new approach to this problem: we show that for a general class of subdivision schemes, regularity can be inferred from the properties of a sufficiently close linear approximation, and injectivity can be verified by computing the index of a curve. An additional advantage of our approach is that it allows us to prove C1-continuity for all valences of vertices, rather than for an arbitrarily large, but finite number of valences. As an application, we use our method to analyze C1-continuity of most stationary subdivision schemes known to us, including interpolating Butterfly and Modified Butterfly schemes, as well as the Kobbelt's interpolating scheme for quadrilateral meshes.

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Copyright © 1998-1999 Denis Zorin