Résumé: Parametric- surface tessellation is one of the most important algorithms for CAGD applications. This paper presents a new parametric- surface tessellation method based on degree reduction: ( 1) a given parametric surface ( or NURBS surface) of degrees ( p.... q is decomposed into a set of Bezier surfaces, ( 2) the Bezier surfaces are converted into a set of bilinear surfaces by applying consecutive stepwise degree reduction processes combined with adaptive subdivision — each degree reduction step, a Bezier surface is adaptively subdivided until the approximation error from degree reduction is smaller than the corresponding step tolerance, ( 3) the bilinear surfaces are converted into a triangular net. The proposed method guarantees the resulting piecewise- planar approximant to deviate from the original parametric surface within a pre- de .ned tolerance, and to form a ‘‘topologically ’’water- tight triangular net.

Langue: Anglais