Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!columbia!rutgers!sri-unix!sri-spam!mordor!lll-tis!ames!ucbcad!ucbvax!decvax!savax!elrond!amamaral From: amamaral@elrond.CalComp.COM (Alan Amaral) Newsgroups: comp.graphics Subject: Re: Ray tracing and caustics. Message-ID: <1038@elrond.CalComp.COM> Date: Mon, 13-Jul-87 10:06:11 EDT Article-I.D.: elrond.1038 Posted: Mon Jul 13 10:06:11 1987 Date-Received: Tue, 14-Jul-87 03:47:22 EDT References: <219@sugar.UUCP> Organization: Calcomp, A Lockheed Company, Hudson, NH, USA Lines: 25 Keywords: ray-tracing caustics algorithm reality In my last posting I might have given the mistaken impression that the rendering equation does reverse ray tracing. This is not the case. It works using distributed ray tracing techniques, but instead of creating a ray tree consisting of refracted, AND reflected, AND other rays it ONLY picks one ray to follow using monte carlo techniques. Also, instead of picking very few initial rays and relying on many second, third, forth, etc. generation rays (it is interesting to note that they really contribute much less to the pixel than do the first generation rays) it picks a larger number (i.e. ~40) of first generation rays distributed properly. By the way, it's not obvious, but caustics basically fall out of this automatically because as a ray hits an object another ray is generated (randomly, direction based on the reflectivity of the intersected object) and if the intersection point is close to another object (a transparent sphere for example), it will intersect the sphere some of the time, thus picking up illumination from it. This also happens with objects that are not transparent, and this mimics radiosity results closely. -- uucp: ...decvax!elrond!amamaral I would rather be a phone: (603) 885-8075 fool than a king... us mail: Calcomp/Sanders DPD (PTP2-2D01) Hudson NH 03051-0908