POV-Ray : Newsgroups : povray.beta-test : Known bugs 9 Mar 2002 : Re: Known bugs 9 Mar 2002 Server Time
30 Jul 2024 00:25:19 EDT (-0400)
  Re: Known bugs 9 Mar 2002  
From: Tim Nikias
Date: 16 Mar 2002 06:52:39
Message: <3C93322D.CAE0D688@gmx.de>
> * Bicubic patch bug (job000202)
>   (Bicubic patch triangles disappear in some circumstances.)
>   Reported in:
> Bicubic patch triangles disappear
> http://news.povray.org/3c23b26c@news.povray.org
>

I'd say this has to do with the typical floating point precision
problems. Solving polynomials for bicubic patches on very
small scales might be something the floats in POV cannot
handle, and thus they "leak" information needed for the
triangles.
I'm not big algorithm guy, and have no information on the
algorithms for bicubic-patches, but perhaps this could be
solved somehow by internally scaling the patch large enough
to be handled (like "normalizing" the patch to a certain size),
calculating the patch, and then scaling it back again could
fix the problem, but, as said, I've no idea if that is possible
or not.

>   Bugs with no official confirmation:
>   ----------------------------------
>
> * Crash with empty scene
>   (Not properly confirmed. Most people report no problems.)
>   Reported in:
> Crash with no objects in scene
> http://news.povray.org/3bd985b0@news.povray.org
> POV-Crash on empty scenes
> http://news.povray.org/3C19B9EA.D2E16FBC@gmx.de
>

I've experienced the problem and it was gone in just this new
beta 13, using a 1.4 GHZ Athlon, Win98 and 512 MB RAM.

--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html


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