Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!columbia!rutgers!cbmvax!vu-vlsi!swatsun!rice From: rice@swatsun (Dan Rice) Newsgroups: comp.graphics Subject: Wanted: Clever Intersection Tests Message-ID: <1222@byzantium.swatsun.UUCP> Date: Wed, 15-Jul-87 14:30:48 EDT Article-I.D.: byzantiu.1222 Posted: Wed Jul 15 14:30:48 1987 Date-Received: Sat, 18-Jul-87 01:47:58 EDT Organization: Swarthmore College, Swarthmore PA Lines: 17 Keywords: ray tracing I'm in the midst of writing a ray-tracer, and I would be very interested in any clever and unusual intersection tests that people have come across. For example, one I saw recently calculated the intersection of a ray with a sphere by finding the closest approach of the ray to the center of the sphere with two dot products, and then found the actual intersection point by forming a triangle with the intersection point, the sphere center, and the point of closest approach. Other ray-tracers that I've seen calculate this intersection by solving a quadratic equation for the intersection point directly. I'm curious to see if there are similar examples of clever intersection tests beating brute- force tests. I'd appreciate examples or source, or pointers to literature about geometric intersection tests. -- - Dan Rice, Swarthmore College, Swarthmore PA 19081 ...!sun!liberty!swatsun!rice ...!seismo!bpa!swatsun!rice