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From: Chambers
Subject: Apparent AA error
Date: 9 Feb 2006 19:39:24
Message: <43ebe0bc@news.povray.org>
This scene
---
camera {
	location <20,50,-20>
	look_at <0,-5,20>
}

plane {
	y,0
	pigment {checker color rgb 2, color rgb y}
	scale 40
	translate -y*20
}

light_source {
	<0,0,30> color rgb 1
}
---
when rendered with AA 0.1, AA depth 1, and sampling method 2, artifacts 
are displayed near the borders between white and green.

The problem is that some "thread blocks" have a noticeably different 
brightness than the neighboring blocks.  I actually noticed this on a 
much more complex scene, and reduced it to this sample.

Increasing the depth or threshold will reduce and eventually eliminate 
these errors.

...Chambers


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From: Chambers
Subject: Re: Apparent AA error
Date: 9 Feb 2006 19:41:18
Message: <43ebe12e$1@news.povray.org>
BTW, I found some posts about errors with method 1, but I'm assuming 
this is a different bug since it's with method 2.

...Chambers


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From: Chambers
Subject: Re: Apparent AA error
Date: 9 Feb 2006 20:08:23
Message: <43ebe787$1@news.povray.org>
Sorry, I'm using the revised sse2 build of beta 11c that Chris Cason 
provided (3.7.0.beta.11c.icl8-sse2.win32).


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From: Warp
Subject: Re: Apparent AA error
Date: 10 Feb 2006 05:51:02
Message: <43ec7016@news.povray.org>
Does it happen only in the preview window, or do the artifacts get to
the final image file too? (I can't test myself right now...)

-- 
                                                          - Warp


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From: Chambers
Subject: Re: Apparent AA error
Date: 10 Feb 2006 17:06:34
Message: <43ed0e6a$1@news.povray.org>
Warp wrote:
>   Does it happen only in the preview window, or do the artifacts get to
> the final image file too? (I can't test myself right now...)
> 

I checked, and these artifacts are present in the final image file.

...Chambers


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From: Chambers
Subject: Re: Apparent AA error
Date: 13 Feb 2006 18:46:46
Message: <43f11a66$1@news.povray.org>
Can someone else verify this, or is it just on my machine?

...Chambers


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From: Bob Hughes
Subject: Re: Apparent AA error
Date: 14 Feb 2006 18:15:50
Message: <43f264a6$1@news.povray.org>
"Chambers" <bdc### [at] yahoocom> wrote in message 
news:43f11a66$1@news.povray.org...
> Can someone else verify this, or is it just on my machine?

Didn't happen that way here, using a Pentium 4-M and ATI Radeon video card, 
only has increased jaggies due to the AA depth of 1. However, the AA method 
1 blockiness did occur when I checked that.

Rendered using the regular beta 11c executable and saw the same results... 
method 2 okay, method 1 not.

Bob


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From: Thorsten Froehlich
Subject: Re: Apparent AA error
Date: 14 Feb 2006 19:17:05
Message: <43f27301$1@news.povray.org>
Chambers wrote:
> The problem is that some "thread blocks" have a noticeably different 
> brightness than the neighboring blocks. 

Actually, this observation while appearing plausible, is not the reason. 
That the problem appears at the thread blocks is due to the way POV-Ray 
decides when to do supersampling (it does that for each block). It so 
happens that there is a bug in computing the average of supersampled pixels 
that carries on as soon as the first supersample is taken. This results in a 
rather interesting chain reaction causing all remaining pixels in a block to 
appear different. And the checker pattern happens to be well at exposing 
that bug. That said, I am still searching for the actual cause in the source 
code, but no doubt will find it eventually ;-)

	Thorsten


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From: Invisible
Subject: Re: Apparent AA error
Date: 15 Feb 2006 10:52:16
Message: <43f34e30$1@news.povray.org>
> That said, I am still searching for the 
> actual cause in the source code, but no doubt will find it eventually ;-)

Go Thorsten! Go Thorsten!

*dances*


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From: Chambers
Subject: Re: Apparent AA error
Date: 15 Feb 2006 18:43:32
Message: <43f3bca4@news.povray.org>
Invisible wrote:
>> That said, I am still searching for the actual cause in the source 
>> code, but no doubt will find it eventually ;-)
> 
> Go Thorsten! Go Thorsten!
> 
> *dances*

I'm just glad someone else verified it - I was starting to think it was 
all in my head :)

...Chambers


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