Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!gatech!bloom-beacon!bu-cs!m2c!ulowell!apollo!scofield From: scofield@apollo.uucp (Cary Scofield) Newsgroups: comp.graphics Subject: Re: Ray tracing and caustics. Message-ID: <36098418.352b@apollo.uucp> Date: Mon, 13-Jul-87 12:07:00 EDT Article-I.D.: apollo.36098418.352b Posted: Mon Jul 13 12:07:00 1987 Date-Received: Tue, 14-Jul-87 05:48:23 EDT References: <219@sugar.UUCP> Reply-To: scofield@apollo.UUCP (Cary Scofield) Organization: Apollo Computer, Chelmsford, MA Lines: 39 Keywords: ray-tracing caustics algorithm reality In article <219@sugar.UUCP> peter@sugar.UUCP (Peter DaSilva) writes: > >It has occurred to me that I have never seen such an effect in ray-traced >images. It shouldn't be too hard: you would have to reverse ray-trace from >the light source for each transparent object and add the caustic to the >texture map for each matte object it eventually falls on. Has anyone >considered doing this? > See: "Backward ray tracing" by James R. Arvo "Reflection and refraction model for ray tracing" by Masa Inakage both of the above papers are in the 1986 SIGGRAPH Course Notes volume entitled "Developments in Ray Tracing". Also see: "The Rendering Equation" by James T. Kajiya from the 1986 SIGGRAPH Proceedings, pp. 143-150. Arvo's paper describes, in detail, an algorithm pretty close to your idea. In Kajiya's paper, the caustics were a natural by-product of the his terra-flop rendering algorithm. If you're inclined to "cheat", use Arvo's method -- it's much faster, even if a little cumbersome to implement. -- Cary Scofield - Graphics Software decvax!wanginst!apollo!scofield Apollo Computer Inc. 270 Billerica Road Chelmsford, MA 01824