PARALLEL IMPLEMENTATION OF AN INTERACTIVE RAY-TRACING ALGORITHM

One of the most-used rendering algorithms in Computer Graphics is the Ray-Tracing. The ''standard'' (Whited like) Ray-Tracing(1) is a good r endering algorithm but with a drawback: the time necessary to produce an image is too large (several hours of CPU time are necessary to make a good picture of a moderately sophisticated 3D scene) and the image is only ready to be observed at the end of processing. This kind of si tuation is difficult to accept in systems where interactivity is the f irst goal. ''Increasing Realism'' In Ray-Tracing tries to avoid the pr oblem by supplying the user with a preview of the final image. This pr eview can be calculated in a considerably shorter time but permits tha t, with some margin of error, the user can imagine (even see, sometime s) some final effects. With more processing time the image quality con tinues improving without loss of previous results. The user can, at an y time, interrupt the session if the image does not match what he want s. Simultaneously with the above idea, it is necessary to accelerate i mage production. Parallelism is then justified by the need of more pro cessing power. The aim of this text is to describe the Interactive Ray -Tracing Algorithm implementation, using a parallel architecture based on Transputers. An overview of the architecture used is presented and the main parallel processes and related problems are discussed.