POV-Ray : Newsgroups : povray.binaries.images : Mesh2 shadow problem... Server Time
6 Aug 2024 21:40:27 EDT (-0400)
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From: Hasan3
Subject: Re: Mesh2 shadow problem...
Date: 21 Nov 2006 16:10:01
Message: <web.456369f2aedcdc5124db0b270@news.povray.org>
Florian Brucker <tor### [at] torfboldcom> wrote:
> > Florian Brucker wrote:
> >> Looks like smooth triangle artifacts:
> >
> >   No, that's not it. The correct url is:
> >
> > http://tag.povray.org/povQandT/TheShadowLineArtifact/index.html
>
> Ah, OK. Thanks for pointing that out.
>
>
> Regards,
> Florian

Florian, thanks for explanation. I have read this article :
"Firstly, don't think that it is a bug in POV-Ray. It isn't a bug, but a
real problem caused be the lighting model used in the renderer engine that
is quite difficult to surpass. It's not a problem in POV-Ray in particular,
but a problem in raytracing in general. Every raytracer will have this same
problem when using perturbed surface normals (unless there's some fix coded
into it)."

I rendered this object with other engines, for example Yafray :

I think, this is a deficiency for Povray..

Regards,
Hasan


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From: Tom York
Subject: Re: Mesh2 shadow problem...
Date: 28 Nov 2006 16:00:00
Message: <web.456ca28aaedcdc517d55e4a40@news.povray.org>
"Hasan3" <PRO### [at] Yahoocom> wrote:

> Florian, thanks for explanation. I have read this article :
> "Firstly, don't think that it is a bug in POV-Ray. It isn't a bug, but a
> real problem caused be the lighting model used in the renderer engine that
> is quite difficult to surpass. It's not a problem in POV-Ray in particular,
> but a problem in raytracing in general. Every raytracer will have this same
> problem when using perturbed surface normals (unless there's some fix coded
> into it)."
>
> I rendered this object with other engines, for example Yafray :
>
> I think, this is a deficiency for Povray..

Clearly, the other engines have a fix for this coded in. But it is a problem
with the raytracing algorithm and modified normals, rather than a defect in
the way POV implements the algorithm (a bug).

I think there is at least one unofficial version of POV with a fix for this.
I think Slime-POV had one (but IIRC it's based on POV 3.5). There may be
others.

Tom


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From: Tom York
Subject: Re: Mesh2 shadow problem...
Date: 28 Nov 2006 16:10:01
Message: <web.456ca53baedcdc517d55e4a40@news.povray.org>
POV-Sub, a modification of 3.6, might be able to fix this via run-time
subdivision:

http://www.cise.ufl.edu/~xwu/Pov-Sub/

It's still subdivision but your modelling software won't be generating the
extra faces.


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