"AnaMark" <mh### [at] homologde> wrote:
> Alain <ele### [at] netscapenet> wrote:
> > > White spots appear at the edges of the cutted torus. [...]
> > >
> > > This is my scene file:
> > > [...]
> > >  intersection {
> > >   torus { 2 , 0.25 }
> > >   plane { -x, 0 }
> > Using 0.01 get rid of the white pixels.
>
> I know; I already tried this (and many, many other variations).
> Unfortunately, this is an animation. And although the white spots do no
> longer appear in this image, they will appear in another image at another
> place. So nothing is won.
>
> > Also, rendering at another size elliminated those white pixels.
>
> Again, it's the same: The spots may disappear in this image. Therefore, in
> another image, new spots will appear. Nothing is won.
>
> BTW: It's a video animation, and so resolution is fixed.
> BTW^2: The final rendering has to be done with anti-aliasing. But using AA
> (doesn't matter, which of the both algorithms will be used) makes the
> problem even worse.
>
> > I think that those are related to
> > presision and rounding errors.
>
> Sorry, but - imo - a raytracer should be capable to properly render such
> simple things as a cut torus, shouldn't it?

The bug is more likely cause by the ray entering and leaving the media at
the same moment, but the tracer only registering the fact that it entered
(thereby finding an infinite amount of white space).  Does adding a crushed
sphere on to each end mess your file up any?  That fixes it.  Values of
..001 or less are probably enough, and only noticible in things like
reflections.

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