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From: coy@ssc-vax (Stephen B Coy)
Newsgroups: comp.graphics
Subject: Re: Ray Tracing Optimization Idea
Keywords: Exploit coherence
Message-ID: <3754@ssc-bee.ssc-vax.UUCP>
Date: 27 Mar 91 15:36:18 GMT
References: <1991Mar21.183340.19319@dartvax.dartmouth.edu> <2448@umriscc.isc.umr.edu> <1991Mar26.183524.1547@pixar.com>
Sender: news@ssc-vax.UUCP
Reply-To: coy@ssc-vax.UUCP (Stephen B Coy)
Organization: Boeing Aerospace & Electronics
Lines: 18

In article <1991Mar26.183524.1547@pixar.com> markv@pixar.com (Mark VandeWettering) writes:
>Regarding the "object cache" for raytracing:

>This same approach is more effective in shadow testing:  cacheing the
>last object that shadowed a given pixel is often quite useful.  The
>MTV raytracer does include shadow cacheing optimizations.

Just a thought.  Since objects that are closer to a light tend to
cast larger shadows it would seem beneficial to shoot shadow rays
from the light to the surface rather than the "normal" way.  This
way the shadow cache should tend to have slightly more coherence.
The extra cost should be zero but I'm afraid that the benefits might
also be as slight.  Comments?

>Mark

Stephen Coy
coy@ssc-vax.UUCP