From: Angus Dorbie (dorbie++at++sgi.com)
Date: 12/05/2000 01:04:23
christopher.g.dorosky++at++lmco.com wrote:
>
> I read the descriptions in the OpenGL book about specular color and shininess, etc. I understand that for colored objects. Is is possible to do anything useful with the material, if it is a textured object?
>
> Does it depend on the texenv settings?
Partly but not really, the problem is that the result of lighting is pre
texture operation.
Lighting produces rgb per vertex, this is interpolated across the
triangle and the texture environment combines the interpolated result
with the texture color either with MODULATE, ADD, or whatever.
This is not close to the gloss effect caused by the physics of lighting.
You don't really want to MODULATE the specular effect with texture but
for example with an ADD texenv it won't make much difference. Ofcource
MUDULATE is the operation you want to perform 99.9% of the time in
conventional rendering.
There is an OpenGL extension calles separate_specular, where the
specular results of lighting are kept separate and interpolated across
the triangle and added *after* the texturing operation. This is not
supported on IRIX based systems, with the *possible* exception of
OCTANE2.
Cheers,ANgus.
>
> Thanks.
>
> Christopher Dorosky
> Lead Electronic Systems Engineer - Real Time Simulation
> Lockheed Martin Missiles and Fire Control - Dallas
> christopher.g.dorosky++at++lmco.com
> 972-603-2349
>
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