Hi there,

I’ve been studying rendering and looking at different shaders in my old version of SoftImage (6.5)
Having a stumbling block with the Cook-Torrance shader that one of it’s settings makes the specular highlight disappear altogether.

Specular RGB input works fine as well as the Roughness setting. BUT As soon as I touch the colour sliders for Refraction
it’s the last I get to see the specular highlight. Gone from the renders.
So I can’t set Refraction values with the XSI monolithic Cook-Torrance shader.

Wanted to ask if anyone knows a workaround or maybe a place where I can download a working version
of the Cook-Torrance shader for SoftImage XSI 6.5?

* UPDATE * This actually happens as soon as I touch the Blue slider.
I wonder if the Refraction parameter is working at all?
The other sliders for Refraction don’t seem to do anything.

This is the only shader I’ve had a problem with. All others work fine.

OK I got really frustrated with the distributed version of Cook-Torrance for some reason so I found the official Mental Ray source online at writingshaders.com

I managed to get this “official” version up and running in XSI with minor glitches today.
Conclusion was that maybe I should have paid more attention to what the Refraction sliders are doing and their initial values.

It turns out they’re overdriven to start with and only respond once overdriven.
I don’t know if this is standard Cook-Torrance behavior in other packages but it definitely is the way XSI handles it.

Why I went through all this I really don’t know. At least I can port and compile XSI shaders a lot better now :)
Maybe with the source I can figure what the Refraction parameter is supposed to be doing a bit better now lol

Any case all it really takes to get the highlight back is overdriving the RGB sliders back to 9.0 8.0 5.0.
Again it works with overdriven values just fine. I guess things are not always obvious but as long as they can still get figured..