Path: utzoo!attcan!uunet!convex!killer!ames!vsi1!versatc!ritter
From: ritter@versatc.UUCP (Jack Ritter)
Newsgroups: comp.graphics
Subject: Ray tracing: ray-object intersection
Keywords: Ray Tracing, Intersection, Trivial Rejection
Message-ID: <522@versatc.UUCP>
Date: 30 Sep 88 17:19:50 GMT
Organization: Versatec, Santa Clara, Ca. 95051
Lines: 28


A simple method for fast ray tracing has occurred to me,
and I haven't seen it in the literature, particularly
Procedural Elements for Computer Graphics.
It is a way to trivially reject rays that don't
intersect with objects. It works for primary
rays only (from the eye).  It is:

Do once for each object: 
   compute its minimum 3D bounding box. Project
   the box's 8 corners unto pixel space. Surround the
   cluster of 8 pixel points with a minimum 2D bounding box.
   (a tighter bounding volume could be used).

To test a ray against an object, check if the pixel
through which the ray goes is in the object's 2D box.
If not, reject it.

It sure beats line-sphere minimum distance calculation.


Surely this has been tried, hasn't it?

-- 
       The ultimate realization: everything is everything. (I should know.)
   Jack Ritter, S/W Eng. Versatec, 2805 Bowers Av, Santa Clara, CA 95051
   Mail Stop 1-7.  (408)982-4332, or (408)988-2800 X 5743
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