Re: White spot

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Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Thu, 20 Mar 1997 21:07:52 +0000

On Mar 20, 3:30pm, Yann Andenmatten wrote:
> Subject: White spot
> Hi,
>
> I'm trying to have an shiny textured object. I have set a pfMaterial with
> specular light to (1.0,1.0,1.0) and shininess to 16.0. It's working, but the
> spot on the object isn't white (the color of the spot is defined by the
> texture). The light has also a specular light to (1.0,1.0,1.0).
>
> How can I get a very saturated spot ?
> Any idea ?

It's the GL which is the problem here.

To add the specular highlight after texture modulation you must
render a second untextured pass with a black material and
a (one, one) blendfunction, and polygon offset to avoid zfighting.

As you can surmise, this type of approach can be expensive.
The OpenGL ARB is currently exploring extensions to the API
which may improve this situation on future implementations.

I've been working on multipass shaders in Performer recently so
if you want performer draw callbacks for the above email me and
I can supply some code.

Cheers,Angus.
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