POV-Ray : Newsgroups : povray.binaries.images : Image to "strange experience with the perspective camera and very large hei= Server Time
29 Jul 2024 22:33:23 EDT (-0400)
  Image to "strange experience with the perspective camera and very large hei= (Message 1 to 6 of 6)  
From: MichaelJF
Subject: Image to "strange experience with the perspective camera and very large hei=
Date: 8 Jun 2013 13:45:01
Message: <web.51b36c32debeb340bd686c570@news.povray.org>
Here is the suspicious Image (see bugreports)




Best regards,
Michael


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From: Thomas de Groot
Subject: Re: Image to "strange experience with the perspective camera and very large hei=
Date: 9 Jun 2013 03:18:12
Message: <51b42c34@news.povray.org>
I read your message and I am almost sure this is an epsilon problem, 
same as when Bill Pragnell and me, and others, modelled the Ringworld a 
couple of years ago. For the POV version then in use, an unofficial 
patch was issued, but the problem appeared again with the 3.7 version 
and, as far as I know, has not been corrected. It is a simple matter of 
a more accurate epsilon value. Strictly speaking this is not a bug and 
you can try to avoid the problem by scaling down the HF and elevate the 
camera a bit more until it disappears. Personally I feel that as an 
inelegant solution though, and I would much prefer an appropriate 
epsilon value.

Thomas


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From: MichaelJF
Subject: Re: Image to "strange experience with the perspective camera and very large= hei=3D
Date: 9 Jun 2013 05:20:00
Message: <web.51b447d93fcfdf4170bf48a60@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:
> I read your message and I am almost sure this is an epsilon problem,
> same as when Bill Pragnell and me, and others, modelled the Ringworld a
> couple of years ago. For the POV version then in use, an unofficial
> patch was issued, but the problem appeared again with the 3.7 version
> and, as far as I know, has not been corrected. It is a simple matter of
> a more accurate epsilon value. Strictly speaking this is not a bug and
> you can try to avoid the problem by scaling down the HF and elevate the
> camera a bit more until it disappears. Personally I feel that as an
> inelegant solution though, and I would much prefer an appropriate
> epsilon value.
>
> Thomas

Thanks Thomas, that explains the effect. But it means 0.00003 < epsilon. I had
assumed it smaller. The actual value seems to be ok for most scenes. A smaller
value might result in a severe prolongation of the render times. Best would be
an option within the global settings.

Best regards,
Michael


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From: Thomas de Groot
Subject: Re: Image to "strange experience with the perspective camera and very large=hei=3D
Date: 9 Jun 2013 07:18:42
Message: <51b46492$1@news.povray.org>
On 9-6-2013 11:16, MichaelJF wrote:
> Thanks Thomas, that explains the effect. But it means 0.00003 < epsilon. I had
> assumed it smaller. The actual value seems to be ok for most scenes. A smaller
> value might result in a severe prolongation of the render times. Best would be
> an option within the global settings.

For most scenes indeed, there is no problem. A global settings option 
would be a good alternative.

Thomas


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From: Cousin Ricky
Subject: Re: Image to "strange experience with the perspective camera and very large=
Date: 9 Jun 2013 13:15:01
Message: <web.51b4b77d8750d79f78641e0c0@news.povray.org>
"MichaelJF" <mi-### [at] t-onlinede> wrote:
> Thanks Thomas, that explains the effect. But it means 0.00003 < epsilon. I had
> assumed it smaller. The actual value seems to be ok for most scenes. A smaller
> value might result in a severe prolongation of the render times. Best would be
> an option within the global settings.

I third this suggestion.

Added Flyspray #297.


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From: MichaelJF
Subject: Re: Image to "strange experience with the perspective camera and very large=
Date: 9 Jun 2013 14:45:02
Message: <web.51b4ccd24df183cc70bf48a60@news.povray.org>
"Cousin Ricky" <rickysttATyahooDOTcom> wrote:
> "MichaelJF" <mi-### [at] t-onlinede> wrote:
> > Thanks Thomas, that explains the effect. But it means 0.00003 < epsilon. I had
> > assumed it smaller. The actual value seems to be ok for most scenes. A smaller
> > value might result in a severe prolongation of the render times. Best would be
> > an option within the global settings.
>
> I third this suggestion.
>
> Added Flyspray #297.

Thank you both, I added it to the wish list at the POV 4 discussion.

Best regards,
Michael


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