POV-Ray : Newsgroups : povray.general : Possible interpolation bug Server Time
29 Jul 2024 14:21:58 EDT (-0400)
  Possible interpolation bug (Message 1 to 4 of 4)  
From: Zeger Knaepen
Subject: Possible interpolation bug
Date: 24 Jul 2011 08:19:14
Message: <4e2c0dc2$1@news.povray.org>
It could be I'm doing something wrong, or maybe my computer is, but when 
I render the following code, I would expect a completely white image, 
instead I get little black dots.
When using "interpolate 3" instead of 2, the problem gets worse, and 
"interpolate 4" gives slightly better results, but still gives me black 
dots.

(I tried to minimize the code)
(also, don't use anti-aliasing when trying this, as it may "cover up" 
those black dots :))
(and also, don't render it the same resolution as the function image, 
because then it won't show)

--- START CODE ---
plane {
   z,1
   #local Function=
     function {
       pigment {
         image_map {
           function 5,5 {pigment {rgbt 1}}
           interpolate 2
         }
       }
     }
   pigment {
     function {Function(x,y,z).red}
   }
   finish {ambient 1}
}
--- END CODE ---

I'm using POV-Ray 3.7.0.RC3.msvc9-sse2.win32 on an Athlon64 X2 5600+ 
with 2GB RAM running Windows XP.

Can anyone confirm this problem?


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From: Christian Froeschlin
Subject: Re: Possible interpolation bug
Date: 24 Jul 2011 09:05:54
Message: <4e2c18b2@news.povray.org>
Zeger Knaepen wrote:

> Can anyone confirm this problem?

I see this too with 3.7 RC3 on Windows 7 x64.

Interestingly I get 100% black with interpolation 1,
at all resolutions and even with aliasing.

The pigment direcly applied shows white as expected so
the problem may also be related to the function pattern.


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From: Slime
Subject: Re: Possible interpolation bug
Date: 24 Jul 2011 17:04:49
Message: <4e2c88f1$1@news.povray.org>
> The pigment direcly applied shows white as expected so
 > the problem may also be related to the function pattern.

Perhaps the interpolation is resulting in values of 1.00000001 that are 
being wrapped around to 0.00000001.

  - Slime


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From: Zeger Knaepen
Subject: Re: Possible interpolation bug
Date: 25 Jul 2011 02:29:01
Message: <4e2d0d2d$1@news.povray.org>
On 24/07/2011 23:05, Slime wrote:
>  > The pigment direcly applied shows white as expected so
>  > the problem may also be related to the function pattern.
>
> Perhaps the interpolation is resulting in values of 1.00000001 that are
> being wrapped around to 0.00000001.

ah, yes, that seems to be it :)

changing the pigment to
"
pigment {
   function {min(Function(x,y,z).red,1)}
}
"
solves it!

thanks :)


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