Abstract

Computer generated shaded images have reached an impressive degree of realism with the current state of the art. They are not so realistic, however, that they would fool many people into believing they are real. One problem is that the surfaces tend to look artificial due to their extreme smoothness. What is needed is a means of simulating the surface irregularities that are on real surfaces. In 1973 Ed Catmull introduced the idea of using the parameter values of parametrically defined surfaces to index into a texture definition function that scales the intensity of the reflected light. By tying the texture pattern to the parameter values, the texture is guaranteed to rotate and move with the object. This is good for showing patterns painted on the surface, but attempts to simulate rough surfaces in this way are unconvincing. This paper presents a method of using a texturing function to perform a small perturbation on the direction of the surface normal before using it in the intensity calculations. This process yields images with realistic looking surface wrinkles without the need to model each wrinkle as a separate surface element. Several samples of images made with this technique are included.