Spec map question

[jeremybirn]

Usually specular color - paint darker where a highlight shouldn't appear, brighter for shiny areas. You can use the same map on reflectivity if needed.

Specular rolloff controls the "Fresnel Effect," an angle-based variance to the brightness of your specular highlights and reflections. If you slide it very low, for example, then highlights and reflections in the center of a sphere would get dim, and you'd mostly see the highlights and reflections that were hitting the edges or coming from behind the object. (I'm defining how it works as in the Blinn shader in Maya, implementations may vary...)

-jeremy

[FLCL]

cheers Jeremy, that clears it all up. Should've figure this out along time ago.

many thanks

[rendermaniac]

If you want to change the brightness of the highlight then plugging it into the specualr rolloff makes more sense doesn't it?

The main reason I've seen for using specular colour is to make a surface look more metallic by putting the colour map into it.

Simon

[jeremybirn]

Simon just brought up a good point: If you aren't trying for a metalic look, your specular color should be a greyscale value, and your specular maps should be grayscale maps.

We agree you should be scaling the highlight brightness with a regular spec map, but I think we're using terms from different programs: In programs that don't have a "Ks" as you'd usually find in Renderman, "specular color" is your main control over highlight brightness. And if specular rolloff also governs how much or how little of a Fresnel effect you get, then that's something you want to be able to tweak separately. So I wasn't advocating a wild use of colored specularity when I said to map the specular color, if that makes sense.

-jeremy

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