"Tobias" <Tob### [at] gmxde> wrote in message news:3d67db62@news.povray.org...
> I tried to create a bottle with sor and wondered about a strange black
area.
> It's just at the height of the horizon (wether there is a plane or not).
>
> Is it a bug or a mistake of mine?

That's not exactly a bug, if it's what I think it is without looking. Try
adding the sturm keyword to the sor. And if that doesn't work well enough
try a render with the camera positioned offset above the maximum height of
the bottle. If, when rendering with the camera at various positions
alongside the bottle, a dashed line appears even with the camera then it is
the problem I'm thinking of.
I haven't a good explanation, only that it's something to do with the sor
surface creation formula and rays being traced, which you have guessed by
now. sturm is short for Sturmian root solver and it can help by forcing more
accurate calculation. It hasn't always been perfect though, just so you
know. You might be able to insert more (or less) points to enhance the
surface creation and that can also work for some circumstances.

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