TEXMAP extension thoughts and findings.

[Joshua Delahunty]

On the subject of the TEXMAP spec, another serious issue is the definition of gloss maps

I currently chose to ignore the gloss map option as I was unsure of it's use thinking material properties should be handled by the color number exclusively unless it act's like a mask (which I suspect it is intended to do).

GLOSSMAP is there to allow for reflective ink to render as it does on the actual part.

Take for example this Rock Raiders Torso:

973pag.jpg

The torso has a combination of elements, some of which are opaque (all the black edge lines), some of which might be semi-transparent (not a lot on this torso, I don't think), some of which has a texture that is semi-reflective (most of his vest, though the photo doesn't show this really well), and some of which have a definite solid reflection (the silver ink on the wrench and undershirt).  The GLOSSMAP would be used to indicate texels that should render with high reflectivity, so that the wrench and other aspects would "sparkle" or "shine" when changing the perspective of either the light source or the view point.  If the alpha channel (transparency channel in modern Photoshop) were viewed, it would look like a solid wrench shape, solid undershirt shape, with random speckle over the surface of the vest, for the various points that light should reflect.

As to Benjamin's issue about the RGB being reserved, I believe those should all be set to 0, so the image would appear black in background color, but appear masked (when viewed, for example as a PNG with the alpha channel in effect) to just the alpha values that dictated the gloss.  Had someone implemented them as all FF, we could have dealt with it (all white).

One bit of thinking was that one or more of those channels might later be used for a bump map definition or some other effect(s).  But we were already attempting to build an extension bridge with the GLOSSMAP definition (unproven, just theoretical), so we didn't define those for use 5 years ago, we only reserved them.  We didn't want those three "extra" channels to go to waste, and have to keep glomming on new PNGs with each new feature.

      -- joshua