"Ketil Froyn" <ket### [at] froynname> wrote in message
news:Pin### [at] lexxinfelineorg...
>
> the surface stops being reflective if I make it too "flat". I have
> renedered a sample here, where the object in the centre is supposed to be
> a parabolic mirror pointing at the camera. You can view the image and the
> source at:
>
>   http://ketil.froyn.name/lens.tga
>   http://ketil.froyn.name/lens.pov   (I had to prefix with "www" for
these)
>
> Any hints on how to avoid the brown bands are appreciated

It's the max_gradient being a little too low. Suggested number was above 2
when I rendered the scene and you had it at only 1.5. It turned out okay
then.

> If I can get this solved, I'll be interested in finding out how I can
> calculate exactly the depth of a parabolic surface. As an example, if I
> would like to render a parabolic surface that is 200mm wide and 0.5mm deep
> (let's say my scale is in millimeters), what would my f_paraboloid look
> like?

Egads... I have no idea, sorry.

-- 
Bob H.
http://www.3digitaleyes.com

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