Eli Ewok Brody wrote:
> 
>  I didn't give you any useful information at all. Sorry about that. Here is
> the source for the shader, and a sample file.

Please post such things in povray.binaries.scene-files.  See
also            povray.announce.frequently-asked-questions for the purpose
of the different groups.

> 
>  I bet someone's thought of this before, but the shader is a top-level dust.
> Generally: dust isn't as visible when looked at straight on, when the
> surface normal is at the same angle as the incident ray. Dust is visible,
> however, when looked at at a tangent. That part works nicely.
> 
>  Another thing about dust, though, is the fact that it tends to settle on
> the tops of objects. I like Z-axis being up, so I use that to add another
> factor in the opacity of the dust. This gives me weird bicubic patch
> problems, for some reason.
> 
>  I didn't understand anything you said about vectors. I really don't know
> much about them. (We learn that *next* year in math.....) Guess it's time to
> start reading up. If anything, I bet my understanding of transforming
> vectors is to blame.
> 

It does not seem to have anything to do with PovMan shaders, without the
shader and in official Povray 3.1 you can see the same problems.  It's
simply not possible to make a perfect sphere with bicubic patches.  Try
using the slope pattern and you will see that the normal vector behaves
quite strangely especially at the 'poles' of the 'sphere'.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/

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