Ron Parker wrote:
> 
> On Wed, 04 Oct 2000 18:10:40 +0200, Fabien Mosen wrote:
> >The "virtual" slope (normal perturbation) at that point will
> >always be the same, regardless of the camera position.
> 
> But the appearance of the surface due to that perturbation will vary with
> camera position and lighting.

As is the appearance of the pigment, whose perception is influenced
by the normal of the surface, the lights...

> >However, the finish value returned (coming from reflection,
> >in that example) will be different with a different camera.
> 
> Not true.  Only the appearance of the surface due to the finish will vary.
> The finish itself is constant.

The *definition* of the finish is constant troughout space, but
the resulting finish value, the one that will contribute to the
final aspect, varies with the camera position.

Imagine a scene without a camera.  Can you get the pigment value
of a suface's point ? Yes.  Can you get the normal at that point ?
Yes.  Can you get the color variation caused by reflection at that
point ? No !

As I said earlier, pigment and normal needs a pattern (plain color
pigment being a case where the color_map has an unique value), while
finish isn't based on patterns.

That's why I think that pigment and normal belongs to the same 
level, as they have similar workings, but finish is a different
beast.

Fabien.

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