Curves and Surfaces for CAGD, 5th Edition

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Coons Patches

We have already encountered design tools that originated in car companies; Bézier curves and surfaces were developed by Citroën and Renault in Paris. Two other major concepts also emerged from the automotive field: Coons patches (S. Coons consulted for Ford, Detroit) and Gordon surfaces (W. Gordon worked for General Motors, Detroit).¹ These methods have a different flavor than Bézier or B-spline methods: instead of being described by control nets, they “fill in” curve networks in order to generate surfaces.

A designer does not think in terms of surfaces but rather in terms of “feature curves”; these are lines on a car between which the actual surfaces fit “naturally.” In Color Plate III, we can see some of these lines as boundary ...