Exact Evaluation of Catmull-Clark Subdivision Surfaces Near B-Spline Boundaries
نویسندگان
چکیده
In a seminal paper [5], Jos Stam gave a method for evaluating Catmull-Clark subdivision surfaces [1] at parameter values near an interior extraordinary vertex (EV). The basic idea is to subdivide recursively until the (u, v) parameter to be evaluated is contained in a regular 4×4 grid of control points which define a bicubic B-spline patch. The subdivision steps can be computed very efficiently in the eigenbasis of the subdivision matrix, i.e., by diagonalizing. Stam did not provide details for boundaries, where diagonalization is not always possible, but in related work on Loop subdivision, he used the Jordan Normal Form to evaluate EVs of valence 3 [4]. Evaluation near boundaries was evidently implemented in Maya for Catmull-Clark surfaces but never published. Zorin et al. later published a method for evaluating a family of Loop subdivision schemes, including near boundaries, using a different decomposition [7]. They worked on a similar method for Catmull-Clark but did not publish it.
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عنوان ژورنال:
- J. Graphics Tools
دوره 12 شماره
صفحات -
تاریخ انتشار 2007