POV-Ray : Newsgroups : povray.animations : dancing pixels Server Time
23 Nov 2024 15:07:43 EST (-0500)
  dancing pixels (Message 1 to 3 of 3)  
From: doctor mark
Subject: dancing pixels
Date: 30 May 2007 09:55:01
Message: <web.465d80c44ce94ddb7a6de2d00@news.povray.org>
Hello, I have a question about an animation I was attempting with POV-Ray.
In the animation, the pixels are seen to dance from frame to frame. It is
definitely NOT a problem with the video compression, becasue I scan scroll
through the individual bitmaps and see the same thing. I know POV-Ray says
NOT to use jitter or crand if you are doing animations. I was using a bump
normal to create a concrete texture, which I am beginning to think is the
problem - even though the documentation does not describe this as a random
texture. Is this likely to be the problem? Is there a better way to get
rough-looking textures without running into this problem?


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From: Bryan Heit
Subject: Re: dancing pixels
Date: 30 May 2007 10:11:57
Message: <465d862d$1@news.povray.org>
doctor_mark wrote:
> Hello, I have a question about an animation I was attempting with POV-Ray.
> In the animation, the pixels are seen to dance from frame to frame. It is
> definitely NOT a problem with the video compression, becasue I scan scroll
> through the individual bitmaps and see the same thing. I know POV-Ray says
> NOT to use jitter or crand if you are doing animations. I was using a bump
> normal to create a concrete texture, which I am beginning to think is the
> problem - even though the documentation does not describe this as a random
> texture. Is this likely to be the problem? Is there a better way to get
> rough-looking textures without running into this problem?

The problem most likely stems from using a texture where elements in the 
texture are smaller then the pixels of the image.  As your camera/scene 
moves (even slightly) you end up with a different averaging of these 
small features, resulting in the "dancing pixels".

I think this problem has been mentioned before in this group - if you 
look through past replies you may be able to find a better answer. 
However, when I'm faced with this problem I do one (or several) of three 
things:

1) Alter my texture to increase the feature size to a point where this 
effect goes away
2) Play with the anti-aliasing values
3) Post-edit in my video editing program; usually using a "denoise" or 
"median cut" filter.

Bryan


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From: gregjohn
Subject: Re: dancing pixels
Date: 5 Jun 2007 16:00:02
Message: <web.4665bfcb6196c67940d56c170@news.povray.org>
Also check for coincident surfaces.   Two objects, in or out of a CSG
operation, that have coincident surfaces.


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