The term "shaded computer graphics" refers to computer-generated images in which an intensity is calculated for each of a quarter-million or more resolvabe spots which form a picture. Realistic images of this sort were first synthesized about a decade ago,1,2 and subsequent years have seen considerable research and development. Although these efforts were largely stimulated by the need for visual simulators for training airplane and spacecraft pilots, the resulting techniques and equipment are now available for a broad spectrum of applications.