Shadowing has historically been used to increase the intelligibility of scenes in electron micros-copy and aerial survey. Various methods have been published for the determination of shadows in com-puter synthesized scenes. The display of shadows may make the shape and relative position of objects in such scenes more comprehensible; it is a tech-nique lending vividness and realism to computer an-imation. To date, algorithms for the determination of sha-dows have been restricted to scenes constructed of planar polygons. A simple algorithm is described which utilizes Z-buffer visible surface computation to display shadows cast by objects modelled of smooth surface patches. The method can be applied