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From: jet@karazm.math.uh.edu (J Eric Townsend)
Subject: Re: Real Time ray tracing
Message-ID: <1991Jun27.064357.29001@menudo.uh.edu>
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Organization: University of Houston -- Department of Mathematics
References: <13306@uwm.edu> <billc.3670@cryo.rain.com> <15882@exodus.Eng.Sun.COM>
Date: Thu, 27 Jun 1991 06:43:57 GMT

In article <15882@exodus.Eng.Sun.COM> cmcmanis@stpeter.Eng.Sun.COM (Chuck McManis) writes:
>I saw a demonstration of some real time ray tracing on a massively parallel
>machine (I believe it was a connection machine with something like 4096
>processors) anyway, ray tracing is well enough known that it is probably
>possible to build a dedicated ray tracing vector unit that costs less
>than these massively parallel boxes.

Vector raytracing is tough.  The problem is that there are all
these conditionals mixed in your code.  I read a how-to paper on
vectorizing ray tracing a while back, I think it was (quick grep
of ~/bib) oops, I can't find it.  Take a look at the Ray Tracing
abstracts, there's a copy for ftp from karazm.math.uh.edu.

At any rate, an RS/6000 model 320 with 32Mb of ram is slightly slower
than a SparcStation-2 w/24 Mb of ram on my ray tracer.  Why?  Because
it never has a chance to cache and use multiple instructions.
(If I do exhaustive ray tracing, it's  even worse. :-)


--
J. Eric Townsend - jet@uh.edu - bitnet: jet@UHOU - vox: (713) 749-2126
Skate UNIX! (curb fault: skater dumped)

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