POV-Ray : Newsgroups : povray.general : Radiosity: any parms affected by scale? Server Time
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From: Greg M  Johnson
Subject: Radiosity: any parms affected by scale?
Date: 5 Jan 2005 21:53:43
Message: <41dca837$1@news.povray.org>
I believe I've RTFM on this one.   I have a scene whose objects have 
dimensions in units of big whole numbers-- 3000 radius, etc.-- and trying 
radiosity.

Should any of the radiosity parms be scaled up for big objects-- do any of 
them implicitly have units of "povray dimensions" to them?


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From: GrimDude
Subject: Re: Radiosity: any parms affected by scale?
Date: 5 Jan 2005 22:20:15
Message: <41dcae6f$1@news.povray.org>
I think 'error_bound' is what you are looking for.

- Grim


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From: Greg M  Johnson
Subject: Re: Radiosity: any parms affected by scale?
Date: 5 Jan 2005 22:33:32
Message: <41dcb18c$1@news.povray.org>
I dunno.

3.3.4.2.5  suggests that error_bound is fractional.  Perhaps the answer, is 
(hopefully) "No, no parms implicitly need to be scaled if you scale your 
scene a few orders of magnitude".


"GrimDude" <a36### [at] bellsouthnet> wrote in message 
news:41dcae6f$1@news.povray.org...
>I think 'error_bound' is what you are looking for.
>
> - Grim
>


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From: GrimDude
Subject: Re: Radiosity: any parms affected by scale?
Date: 5 Jan 2005 23:25:50
Message: <41dcbdce$1@news.povray.org>
"Greg M. Johnson" <gregj;-)565### [at] aolcom> wrote in message 
news:41dcb18c$1@news.povray.org...
>I dunno.
>
> 3.3.4.2.5  suggests that error_bound is fractional.  Perhaps the answer, 
> is (hopefully) "No, no parms implicitly need to be scaled if you scale 
> your scene a few orders of magnitude".
>

You can change variables to see how they effect the overall scene easily 
enough. From "3.3.4.3 Tips on Radiosity"

<quote>
If you want to see where your values are being calculated set radiosity 
count down to about 20, set radiosity nearest_count to 1 and set 
gray_threshold to 0. This will make everything maximally patchy, so you will 
be able to see the borders between patches. There will have been a radiosity 
calculation at the center of most patches. As a bonus, this is quick to run. 
You can then change the error_bound up and down to see how it changes 
things. Likewise modify minimum_reuse.
</quote>

Well I know the effects of setting a value too low for a particular view.

- Grim


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From: Rafal 'Raf256' Maj
Subject: Re: Radiosity: any parms affected by scale?
Date: 6 Jan 2005 00:16:36
Message: <Xns95D63FF1AC465raf256com@203.29.75.35>
gregj;-)565### [at] aolcom news:41dca837$1@news.povray.org

> Should any of the radiosity parms be scaled up for big objects-- do
> any of them implicitly have units of "povray dimensions" to them?

AFAIK one (and hopefully only) problem is with very small objects, or 
camera that has small angle,

http://www.raf256.com/povray/bug/radiosity-orthographic

Ofcourse using _huge_ object could result in lost of precision and out of 
double range errors, and AFAIK using objects with details < 1.0 could lead 
to some shadow problems.

Btw, there fore I think it is best to create scene in with typical object 
has about 100 units (like we create a model of ufo - start with sphere{0 
100}, model of a room - box{-50,+50} and so on), and in with no datails are 
smaller then 0.1 (with room example - if YOu are planning later to zoom-in 
on some objects like cofee mug, or computer monitor perhaps start with 1000 
unit room).


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


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From: GrimDude
Subject: Re: Radiosity: any parms affected by scale?
Date: 6 Jan 2005 00:57:03
Message: <41dcd32f@news.povray.org>
Seems like this would be pretty easy to test (not that I'm going to do it 
just now). Simply make a simple cylinder/sphere/cube radiosity scene (on a 
white surface of course) and then render with a particular variable (say 
error_bound), scale it up by a huge factor, and test to see how changes in 
the variable effect the overall.

- Grim


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From: Warp
Subject: Re: Radiosity: any parms affected by scale?
Date: 6 Jan 2005 05:17:39
Message: <41dd1043@news.povray.org>
Greg M. Johnson <gregj;-)565### [at] aolcom> wrote:
> I believe I've RTFM on this one.   I have a scene whose objects have 
> dimensions in units of big whole numbers-- 3000 radius, etc.-- and trying 
> radiosity.

> Should any of the radiosity parms be scaled up for big objects-- do any of 
> them implicitly have units of "povray dimensions" to them?

  POV-Ray 3.1 had a problem with the overall scale of the scene when using
radiosity. The problem was fixed in POV-Ray 3.5, so the overall scale of
the scene should be irrelevant.

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -


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