Path: utzoo!utgpu!water!watmath!clyde!att!rutgers!apple!flaig
From: flaig@Apple.COM (Charles Flaig)
Newsgroups: comp.graphics
Subject: Re: Ray tracing: ray-object intersection
Keywords: Ray Tracing, Intersection, Trivial Rejection
Message-ID: <18099@apple.Apple.COM>
Date: 2 Oct 88 22:18:08 GMT
References: <522@versatc.UUCP>
Reply-To: flaig@apple.com.UUCP (Charles Flaig)
Organization: Apple Computer Inc, Cupertino, CA
Lines: 24

In article <522@versatc.UUCP> ritter@versatc.UUCP (Jack Ritter) writes:
>
>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:
 ^^^^^^^^^^^^^^^^^^^^^^^^

Unfortunately, that's the problem.  You also need to intersect rays from
each of the light sources, which adds a lot of storage with your approach.
And in ray tracing a "typical" scene, you are going to have some transmission
and a lot of reflection for secondary rays which leads to the "primary rays
from the eye" being only a minor part of the overall calculation.  Trying to
do some decent diffusive lighting leads to even more secondary rays....

The nice thing about a sphere is that it works uniformly for all rays, and
is fairly simple.

(If I got anything wrong, flame the net, not me. :-)

--Charles
  flaig@apple.com