Newsgroups: comp.graphics
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!kyriazis
From: kyriazis@iear.arts.rpi.edu (George Kyriazis)
Subject: Re: Ray Tracing Optimization Idea
Message-ID: <9B}=P0$@rpi.edu>
Keywords: Exploit coherence
Nntp-Posting-Host: iear.arts.rpi.edu
Organization: Rensselaer Polytechnic Institute, Troy NY
References: <1991Mar21.183340.19319@dartvax.dartmouth.edu>
Date: 23 Mar 91 20:18:59 GMT
Lines: 30

In article <1991Mar21.183340.19319@dartvax.dartmouth.edu> npw@eleazar.dartmouth.edu (Nicholas Wilt) writes:
>I had a simple, interesting idea to make tracing primary rays more
>efficient.  Cache the last object intersected; intersect with it
>first and if hit, determine whether it is still the nearest object as
>follows:
>	1. Fire a ray from the intersection back at the eye
>	2. If no object is intersected, the cached object is still nearest
>	3. If any objects are intersected, find the farthest intersection
>	   that's not beyond the eye.  This is the new nearest intersection
>	   to the eye.
>

1. Since you are firing a ray from the object to the eye anyway, why not
   fire a ray from the eye to the object like you are doing normally?  
   You'll be looking through the object database anyway.  It all depends
   if the scene complexity is higher infront of the eye or behind the eye.
   When you fire a ray towards the eye, you may have complicated objects
   behind you that you may hit now that you did not hit before.  If you
   are using some kind of voxel technique to walk through the scene, I
   think that you'll be just complicating the intersection algorithm.

2. Why do you think that works just for primary rays?  It looks to me
   that you can perform your optimization for non-primary rays also.


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George Kyriazis
kyriazis@iear.arts.rpi.edu kyriazis@rdrc.rpi.edu kyriazis@orion.phys.rpi.edu
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