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From: Tim_Buxton@UM.CC.UMICH.EDU
Newsgroups: comp.sys.sgi
Subject: Quantitative IRIS Lighting Models
Message-ID: <6494368@um.cc.umich.edu>
Date: 11 Jul 90 03:56:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
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What is the best software approach for predicting the TRUE
appearance of a given material surface in light(s) of a
given color from a given angle?  Say you want to know if a machine or
 person can recognize an object in a given light
for sorting on an assembly line, or some other quantitative
application.
 
 
Faced with this sort of task, I am requesting the
 experiences of people modeling the physics of materials in
 light on IRISes. This includes the faithful modeling of:
 
  Bidirectional surface reflectance characteristics
 
  Spectral characteristics of incident and reflected light
      from several sources
 
  Shadowing
 
 
How would you rate the following alternatives on SGI for
 faithful image reproduction and computation requirements:
 
   1. User-written lighting model programs in RGB mode
 (based on a recent helpful posting by Paul Haeberli)
 
   2. Commercial rendering programs such as Personal
 Visualizer, RenderMan, etc. 
 
   3. Raytracing programs such as the BRL-CAD lgt model
 
 
How in any of these approaches do you quantify lumens input
 to the scene when light intensity is specified in 0.0 to
 1.0  or 0-255 RGB color intensities?  How can you interpret
 lumens output?  How can you model the effect of a color
 filter or video camera bandpass?
 
Is there any coverage of quantitative modeling in the SGI
 graphics courses?
 
How do the capabilities of the Power Vision (VGX)series affect
 the above?  For instance, how much does the hardware
 texturing or anti-aliasing or blurring capability  help in
 physical modeling?
 
There is helpful material on specular and diffuse
 reflectance, etc. in the User's Guide on Lighting, as well
 as information in the Modeling on the IRIS pamphlet and
 Wavefront Personal Visualizer, and the BRL-CAD manual.  All
 seem possible candidates.  Before going in three directions
 at once, though I think I and many others would be helped
 by recommendations of those who have worked with 
 modeling quantitatively correct images.
 
Thanks in advance for your response.
 
 
                             -Tim Buxton
                              OptiMetrics, Inc.
                              Tim_Buxton@um.cc.umich.edu