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From: jwp@utah-cs.UUCP (John W Peterson)
Newsgroups: net.graphics
Subject: Re: Color calc. for ray tracing, HELP
Message-ID: <3106@utah-cs.UUCP>
Date: Fri, 9-Nov-84 03:45:13 EST
Article-I.D.: utah-cs.3106
Posted: Fri Nov  9 03:45:13 1984
Date-Received: Sat, 10-Nov-84 05:46:18 EST
References: <31000007@uiucdcs.UUCP>
Organization: Univ of Utah CS Dept
Lines: 31


  I'm starting on a ray tracing project but I'm having one problem.
  I don't know how to convert the intensity calculations from the 
  reflection model into the appropriate RGB values for display.
  I know it has something to do with integrating certain functions 
  to get the XYZ values and then transforming these to the RGB space 
  via a matrix multiplication.

What you're refering to with the transformation matrices is probably 
Cornell style color and shading models.  These are well described; they
wrote a couple of papers on the subject in Siggraph '79 (see the procedings
for that year).  I believe it falls under the title "color gamut
transform pairs", I don't have the procedings handy, but it's pretty
easy to find it.  A more recent treatment of the subject, dealing with
ray-tracing, can be found in Roy Hall's paper, "A Testbed for Image
Synthesis", Published in IEEE Computer Graphics and Applications last year.

However, for a run-of-the-mill ray tracer using those transformations is
probably overkill.  Several people here at Utah have written ray-tracing
systems producing very nice images by simply treating the RGB channels
as completly separate.  In this case, all objects and light sources have
their colors specified in terms of Red, Green, and Blue, and
Whitted's recursive shading equation is applied to each of these terms
individually.

   I'm using a RAMTEK capable of 1024 simultaneous colors determined 
   by an 8-bit value for each component of RGB.

Spencer Thomas posted a program a couple months back that converted images 
defined with separate RGB channels into a single 8 bit image.  (Though
you can probably change it to do a better job with 10 bits to work with).