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From: Warp
Subject: Small error_bound increases artifacts?
Date: 16 Mar 2001 09:55:17
Message: <3ab22954@news.povray.org>
It seems that the smaller the error_bound value, the more likely you'll
get odd-looking radiosity artifacts in corners. Is this so? And what can
be done about it?
  The bad thing about specifiying a larger error_bound (1 or larger) is that
you don't get the natural darkening in the corners as you should.

-- 
char*i="b[7FK@`3NB6>B:b3O6>:B:b3O6><`3:;8:6f733:>::b?7B>:>^B>C73;S1";
main(_,c,m){for(m=32;c=*i++-49;c&m?puts(""):m)for(_=(
c/4)&7;putchar(m),_--?m:(_=(1<<(c&3))-1,(m^=3)&3););}    /*- Warp -*/


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From: Christoph Hormann
Subject: Re: Small error_bound increases artifacts?
Date: 16 Mar 2001 10:11:51
Message: <3AB22D36.5A96874@gmx.de>
Warp wrote:
> 
>   It seems that the smaller the error_bound value, the more likely you'll
> get odd-looking radiosity artifacts in corners. Is this so? And what can
> be done about it?

If you use the same 'count' value, this is natural, decreasing error_bound
nearly always requires higher count values (nearest_count could help in
some cases too).

It also seems obvious to me that corners are preferred places for
persistent artefacts. 

One thing that often bothers me a bit are certain structures on outside
corners like in:

http://www.schunter.etc.tu-bs.de/~chris/pov/radB_X.jpg

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/


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From: Alberto
Subject: Re: Small error_bound increases artifacts?
Date: 16 Mar 2001 19:19:41
Message: <3AB2AD77.454D3A59@usb.ve>
Warp wrote:
> 
>   It seems that the smaller the error_bound value, the more likely you'll
> get odd-looking radiosity artifacts in corners. Is this so? And what can
> be done about it?
>   The bad thing about specifiying a larger error_bound (1 or larger) is that
> you don't get the natural darkening in the corners as you should.
> 

Hi.

I have been applying this "rule" with some success. If you set the
error_bound value to x, then set the low_error_factor to x/8 or x/10.
The rule fails if the error_bound is to small though.

Hope this may help.

Alberto.


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From: Alberto
Subject: Re: Small error_bound increases artifacts?
Date: 16 Mar 2001 19:36:43
Message: <3AB2B170.560FD372@usb.ve>
In other words, I agree with you in the sense that the lower the
error_bound, the greater the probability you'll get radiosity artifacts.

Alberto.


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From: Tony[B]
Subject: Re: Small error_bound increases artifacts?
Date: 17 Mar 2001 09:52:03
Message: <3ab37a13@news.povray.org>
> One thing that often bothers me a bit are certain structures on outside
> corners like in:

I don't see anything wrong... would you mind circling the trouble spot?


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From: Christoph Hormann
Subject: Re: Small error_bound increases artifacts?
Date: 17 Mar 2001 11:23:19
Message: <3AB38F78.64E3CEE0@gmx.de>
"Tony[B]" wrote:
> 
> I don't see anything wrong... would you mind circling the trouble spot?

I meant the lower right near corner of the 'box', the floor is very bright
directly at the corner and gets darker to both sides.

It's better visible in:

http://www.schunter.etc.tu-bs.de/~chris/pov/radtest01.png

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/


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From: Tony[B]
Subject: Re: Small error_bound increases artifacts?
Date: 18 Mar 2001 10:34:40
Message: <3ab4d590@news.povray.org>
OK. Now I see it. That is an effect I too have noticed. Use a high enough
count and it disappears. :\


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