Department of Computer Science, University of Calgary

Calgary, Alberta, Canada T2N 1N4

{pwp|samavati|smithco|radekk}@cpsc.ucalgary.ca

In recent years, subdivision has emerged as a major geometric modeling technique. Algorithms for generating subdivision curves are often specified in terms of iterated matrix multiplication. Each multiplication maps a globally indexed sequence of points that represents a coarser approximation of the curve onto a longer sequence that represents a finer approximation. Unfortunately, this use of matrices and indices obscure the local and stationary character of typical subdivision rules.

We introduce parametric context-sensitive L-systems with affine geometry interpretation as an alternative technique for specifying and generating subdivision curves. This technique is illustrated using Chaikin, cubic B-spline, and Dyn-Levin-Gregory (4-point) subdivision schemes as examples. L-systems formalize subdivision algorithms in an intuitive, concise, index-free manner, reflecting the parallel and local character of these algorithms. Furthermore, L-system specification of subdivision algorithms directly leads to their computer implementation.

P. Prusinkiewicz, F. Samavati, C. Smith, R. Karwowski: L-system description of subdivision curves. International Journal of Shape Modeling 9 (1), pp. 41-59.

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