clipka <ano### [at] anonymousorg> wrote:
> Zeger Knaepen schrieb:
> > I'm not sure about the highlights-block.. If that gets through, I believe
> > there should also be a diffuse-block.
>
> Might become worth it - it has already ceased to be a strictly
> single-value statement.
>
> > And to be honest, I actually like Reactor's idea of allowing a color_map.
> >
> > Something like this:
> > ...
>
> Hm... that's actually a neat idea! So far I had understood the idea to
> be about getting a different brightness or roughness for different
> points on the object - which I wouldn't have considered too
> entertaining, given that this can be achieved with texture maps already.
>
> But modulating the highlight intensity (or even colour) according to the
> highlight falloff - that's something new indeed.
>
> > color_maps would allow for a whole range of special effects, including
> > simulating the effects of combined highlights.
>
> Yup.

I've been playing with the SSLT stuff the last 2 days and I noticed that in the
Jensen SSLT SIGGRAPH paper there's a third RGB Diffuse Reflectance parameter
(like a color_map for highlights, yes?) used to fine tune the material. So that
would just mean extending the existing diffuse component of a finish to use a
full RGB color vector instead of an assumed grayscale color vector
as it is currently, which makes a lot of sense to me (and a second vector for
the backlit stuff that Clipka did).

Well, I've been thinking about this for a while, and wondering... Xander
Enzmann's (a former POV-Ray contributor) Polyray was doing something like that
15 years ago (among other things, like using various microfacet highlight
distribution models). Take a read through the old Polyray docs at Paul Bourke's
website: http://local.wasp.uwa.edu.au/~pbourke/dataformats/polyray/
It's like listening to an old Led Zeppelin album; you sometimes forget how good
they were back in those days.

Regardless, accurate simulation of different physical materials requires
different mathematical models to handle the various cases. I know what (and
who) Phong is, but I'm not really sure what model POV-Ray's "specular"
represents (just a guess - Cook-Torrence?). So, why limit POV-Ray to "phong"
and "specular?" Why not just take into account several shading models for
various materials, just like the high-dollar Hollywood boys do? (and they're
pretty damned convincing most of the time)

That simply means making available various *combinable* shading models for
various materials. Blinn/Phong for plastics, Lambert for simple
non-reflective surfaces, Cook-Torrance for metals, Oren Nayar for rough
surfaces, and Ward-anisotropic for objects with anisotropic reflections like
brushed metal, fur, hair, etc. That's the utmost in flexibility as far as I can
see.

Just my 2 cents.

-Rob

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