POV-Ray : Newsgroups : povray.beta-test : 36.b3.win bright media bug Server Time
1 Nov 2024 05:22:19 EDT (-0400)
  36.b3.win bright media bug (Message 1 to 6 of 6)  
From: Rafal 'Raf256' Maj
Subject: 36.b3.win bright media bug
Date: 9 Apr 2004 12:35:43
Message: <Xns94C6BD1A1EE04raf256com@203.29.75.35>
Bug possible caused by bright emission media.

Bug noticed on:
  PovRay 35 Win32 - NO
  PovRay 35 Linux - NO
  PovRay 36 beta 2 Win32 - YES
  PovRay 36 beta 3 Win32 - YES

I noticed this bug while working on my IFJ logo scene, I didnt had time to 
find minimalistic scene, but I turned off some options in my scene-file so 
it has only importand objects and it doesnt need any textures nor font 
files.

Scene file can be downloaded from:
  http://www.raf256.com/3d/povray/bug/04_0001/raf256_pov_bug_040001.tgz
  http://www.raf256.com/3d/povray/bug/04_0001/raf256_pov_bug_040001.zip
or from p.b.s-f

Bug:
Random bright yellow-white spors probably coused by media. Spots are in 
same collor as media, and appear in reflective surface nearby.
Position of spots is totaly random - it is different each time You render 
same scene file.

Examples of bug posted to p.b.i


-- 
http://www.raf256.com/3d/
Rafal Maj 'Raf256', home page - http://www.raf256.com/me/
Computer Graphics


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From: Thorsten Froehlich
Subject: Re: 36.b3.win bright media bug
Date: 9 Apr 2004 13:31:34
Message: <4076ddf6$1@news.povray.org>
Please read:

>From: Alan Kong <ako### [at] povrayWWWSPAMCOMorg>
>Newsgroups: povray.announce.frequently-asked-questions
>Subject: bug reporting
>Date: Don, 11. Jul 2002 5:32 Uhr
>
> The minimum information to include in your bug report is:
>
> - The version number of POV-Ray you are using, such as 3.1g, 3.5,
> etc. You can see this by selecting About from the Help Menu (in
> POV-Ray for Windows).
>
> - Your operating system. It is surprising how many people fail to
> provide this basic piece of information. We need to know what version
> of Windows, Mac, or unix variant you are running.
>
> - Your system specs; what processor and how much memory.
>
> - A complete description of the problem and what led up to it. It
> will make it a lot easier to track down if you can include a scene
> file that will enable us to duplicate the problem. Please remove
> non-essential parts until you have the *minimum* scene file that will
> reproduce the problem (but do include your camera and light source!).

Sadly, your scene just fails to render for me because it assumes about one
million things, it extremely long and complex, and simply cannot be used to
track down what you think could be a bug.  For all I know it could be a
problem in your complex scene.

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org


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From: Rafal 'Raf256' Maj
Subject: Re: 36.b3.win bright media bug
Date: 9 Apr 2004 14:21:18
Message: <Xns94C6CF005B505raf256com@203.29.75.35>
tho### [at] trfde news:4076ddf6$1@news.povray.org

> Sadly, your scene just fails to render for me because 

It uses only 2 files *.inc, what was the error message?

> For all I know it could be a problem in your complex scene.

Anyway, I found what was the problem, while cleaning up scene for 
bug report (I've shorten it to 40 lines + comments.

This looks loke a realy rare bugs, it's quite funny actualy, the bug is:
a problem with anti-alias of reflection of 2 intersecting media 
containers, if they are putted in bigger hollow object, and when 
media color is very bright.

As for the scene - there are 2 torussed filled with emission media. 
They intersect. Intersection point is beeing reflected in blue object 
behind. When antialias is on, then random pixels near reflection of 
intersection are white.

Scene usses a big hollow sphere (used as background/skysphere in 
oryginal scene) it is needed if we want to see the bug, AFAIK.

So I'm guessing bug has something to do both with media and antialias
 color-clipping.

Should I post .pov file and example render of shorten code to 
p.beta-test.binary ?



The scene source (no external files this time)



==============================================

// (C) 2004 Rafal Maj Raf256 www.raf256.com/povray/
// raf256 povray bug 04/0001 version 001 - breached from: IFJ Logo A ver 0.40.10
(miles >7)
// news.povray.org: Message-ID: <Xns94C6BD1A1EE04raf256com@203.29.75.35>

// reproduce bug:
// (((0))) render with AA to see bug: +w512 +h384 +a0.03 +am2 +r2
// (((1))) enclose scene in big hollow primitive like sphere
// (((2))) use bright emitting media
// (((3))) allow media to be reflected in some other object
// (((4))) have 2 media containers intersecting

#local USE_BIG_SPHERE = 1; // (((1))) set to 1 to see bug

camera { location -30*z look_at 0 translate <-4,3,0>  angle 30 }
global_settings { max_trace_level 20 }
background { rgb .5 }

#if (USE_BIG_SPHERE) sphere { 0 2000 pigment {  rgb .4 }  finish { diffuse 0 ambient
.82 }  hollow } #end

light_source { <-400,700,-600> rgb 1  }

difference {    
  sphere { 0 0.12 scale <1,1,.5> }
  sphere { 0 0.122 scale <1,1,1> translate -z*0.10 }
  
  translate  <-0.2,0,0> + <0.10,0.50,0>
  translate <-.1,-.2,0>  scale 20*<1 , 1, .3>  
  
  pigment { rgb <0.25, 0.65, 1.0> }
  finish { reflection { .23 .38 metallic .35 } } // (((3)))
}
  

union {  
  #macro makeTrak(RX,RY,RZ)
    torus { 3 0.020 rotate x*RX rotate +y*RY rotate z*RZ  hollow 
      pigment { rgbf 1 }
      interior { media {  emission <1,.4,.01>*20 /* (((2))) */  } }
    }
  #end
  
  makeTrak(90,90,  0)
  makeTrak(90,90, 60) // (((4)))
  
  pigment { rgbft <0.70, 0.70, 0.30, 0.40, .20> }
  finish { diffuse 0 ambient .8 }
  interior { media { emission 0.4*<1,.5,.1> } }     
    
  translate <-4,6,0> - z*1.30 + <0.21, -0.22, 0>
}

==============================================


-- 
http://www.raf256.com/3d/
Rafal Maj 'Raf256', home page - http://www.raf256.com/me/
Computer Graphics


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From: Thorsten Froehlich
Subject: Re: 36.b3.win bright media bug
Date: 9 Apr 2004 15:13:41
Message: <4076f5e5$1@news.povray.org>
In article <Xns94C6CF005B505raf256com@203.29.75.35>, "Rafal 'Raf256' Maj" 
<spa### [at] raf256com> wrote:

> This looks loke a realy rare bugs, it's quite funny actualy, the bug is:
> a problem with anti-alias of reflection of 2 intersecting media
> containers, if they are putted in bigger hollow object, and when
> media color is very bright.

Nope, it has nothing to do with anti-aliasing.  If you increase the
resolution to i.e. 4000*3000 you will notice the same spots.

I cannot currently tell you if these spots are normal or not, but my current
guess is that they are.  Still, I will have to take a closer look when I
have time to make sure this is the case.

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org


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From: Rafal 'Raf256' Maj
Subject: Re: 36.b3.win bright media bug
Date: 9 Apr 2004 15:25:19
Message: <Xns94C6D9DA5C560raf256com@203.29.75.35>
tho### [at] trfde news:4076f5e5$1@news.povray.org

> I cannot currently tell you if these spots are normal or not, but my
> current guess is that they are.  Still, I will have to take a closer
> look when I have time to make sure this is the case.

Ok, thanks, maybe I will come up with even shorter scene.

I also thouht that this is normal effect, but as I noticed - this spots are 
different each time YOu render same scene, and same scene should give 
binary identical output, right?  (ofcourse assuming same version, ini 
options, external file, etc), so uninitialized variables (or reading 
uninitialized memory) must be involved somewhere.

-- 
http://www.raf256.com/3d/
Rafal Maj 'Raf256', home page - http://www.raf256.com/me/
Computer Graphics


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From: Hughes, B 
Subject: Re: 36.b3.win bright media bug
Date: 9 Apr 2004 22:44:33
Message: <40775f91$1@news.povray.org>
"Rafal 'Raf256' Maj" <spa### [at] raf256com> wrote in message
news:Xns94C6D9DA5C560raf256com@203.29.75.35...
> tho### [at] trfde news:4076f5e5$1@news.povray.org
>
> > I cannot currently tell you if these spots are normal or not, but my
> > current guess is that they are.  Still, I will have to take a closer
> > look when I have time to make sure this is the case.
>
> I also thouht that this is normal effect, but as I noticed - this spots
are
> different each time

Media uses a sampling antialiasing by default; and jitter too, I believe.
You might want to recheck it using 'jitter 0'. Sorry, I haven't tried your
test script.

Here's where to read about it in the Scene Help: 6.8.2  Sampling Parameters
& Methods

-- 
Bob H.
http://www.3digitaleyes.com


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