Re: Trucation in color computation

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Angus Dorbie (dorbie++at++sgi.com)
Fri, 30 Jul 1999 13:10:22 -0700

In OpenGL the values should not be clamped before the multiplication,
although that may be the result you are seeing. Standard procedure would
be get the latest graphics patch then break it down to a simple OpenGL
sample & file a bug.

Cheers,Angus.

Scott Herod wrote:
>
> Is it reasonable to believe that the truncation of illumination
> values occurs differently on different hardware in OpenGL/Performer?
>
> One of our demo artist recently showed me an example of two
> scenes which look significantly different on an MXE OCTANE and
> ONYX IR. Based on values of colors and lights that she had set
> I can only guess that on the MXE illumination is essentially
> computed as I = MIN( Light_Color * Object_Color, 1 ) while on
> the IR illumination is I = MIN( Light_Color, 1) * MIN( Object_Color, 1).
>
> Is that possible?
>
> Thanks,
>
> Scott Herod
> scott++at++evt.com
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