Florian Brucker <tor### [at] torfboldcom> wrote:
> Thanks for your opinions about that. I hadn't considered that from a 
> mathematical point of view a degenerate cylinder is troublesome 
> (although, from a user's point of view it may not be).

  The problem is simply that if the endpoints of the cylinder are the
same point but the cylinder has a non-zero radius, POV-Ray cannot know how
to orientate the resulting disc.

  Basically there doesn't exist degenerate spheres (the only exceptional
case is a sphere with a radius of 0, but that's just no sphere at all)
or degenerate boxes (creating an infinitely thin "box" is umambiguous
and thus there's no problem). However, a cylinder with a non-zero radius
but with coincident endpoints is a problem because it can't be created
unambiguously.

-- 
                                                          - Warp

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