CASTING CURVED SHADOWS ON CURVED SURFACES.

Abstract

To date, algorithms for the determination of shadows have been restricted to scenes constructed of planar polygons. A simple algorithm is described which utilizes Z-buffer visible surface computation to display shadows cost by objects modelled of smooth surface patches. The method can be applied to all environments, in fact, for which visible surfaces can be computed. This comprehensive algorithm, which permits curved shadows to be cast on curved surfaces, is contrasted with a less costly method for casting the shadows of the environment on a single ground plane. The effects of dither, interpolation, and geometric quantization at different stages of the shadowing algorithms are examined. The special problems posed by self-shadowing surfaces are described.