Parameterized Ray-tracing

Abstract

The construction and refinement of a computer graphics scene is unacceptably slow when using ray tracing. We introduce a new technique to speed up the generation of successive ray traced images when the geometry of the scene remains constant and only the light source intensities and the surface properties need to be adjusted. When the scene is first ray traced, an expression parameterized in the color of all lights and the surface property coefficients of all objects is calculated and stored for each pixel. Redisplaying a scene with a new set of lights and colors then consists of substituting values for the corresponding parameters and re-evaluating the expressions for the pixels. This parameter updating and redisplay takes only a few seconds, as compared to the many minutes or hours required to ray trace the entire scene again, but it uses much more memory and disk space. With suitable expression sharing, however, these storage needs can be reduced to an acceptable level.