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From: Peter Popov
Subject: Radiosity scenes tinted?
Date: 7 Dec 2000 01:39:57
Message: <buau2t4vp90fot0g5m5j5nci06jn5nt7s1@4ax.com>
Why do most rad-only scenes look tinted? They either have a
greenish-yellow tint or a bluish-green (somewhat underwater) tint. I
know it's the pigments and/or light sources people use, but I don't
think that's entirely realistic.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg


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From: Margus Ramst
Subject: Re: Radiosity scenes tinted?
Date: 7 Dec 2000 10:19:36
Message: <3A2FAB0A.D4918A9A@peak.edu.ee>
Peter Popov wrote:
> 
> Why do most rad-only scenes look tinted? They either have a
> greenish-yellow tint or a bluish-green (somewhat underwater) tint. I
> know it's the pigments and/or light sources people use, but I don't
> think that's entirely realistic.
> 

Well, in MegaPOV the default gray_threshold is 0, which  in most cases makes the
radiosity lighting look too saturated IMHO. In regular POV the default is 0.5,
but perhaps people still set it too low to make the rad effects more
conspicuous.

-- 
Margus Ramst

Personal e-mail: mar### [at] peakeduee
TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg
Home page http://www.hot.ee/margusrt


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From: Vahur Krouverk
Subject: Re: Radiosity scenes tinted?
Date: 7 Dec 2000 11:43:58
Message: <3A2FBED1.73EB0A8B@aetec.ee>
Peter Popov wrote:
> 
> Why do most rad-only scenes look tinted? They either have a
> greenish-yellow tint or a bluish-green (somewhat underwater) tint. I
> know it's the pigments and/or light sources people use, but I don't
> think that's entirely realistic.
> 
Arnold set an industry standard?


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From: Kari Kivisalo
Subject: Re: Radiosity scenes tinted?
Date: 8 Dec 2000 02:00:38
Message: <3A308736.209C158F@kivisalo.net>
Margus Ramst wrote:
>
> Well, in MegaPOV the default gray_threshold is 0, which  in most cases makes the
> radiosity lighting look too saturated IMHO.

My tests with the Cornell box indicated that to match their radiosity
engine gray_threshold 0 is required.

Too saturated lighting results from not using assumed_gamma 1.0, light
sources without fade_distance and too saturated surface and light source
colors.

Of course it's possible the Cornell University Program of Computer Graphics
did a sloppy job with their engine but somehow I doubt it.

For artistic purposes it's good to have a tunig parameter for matching
personal tastes.


______________________________________________________________________
Kari Kivisalo                                  http://www.kivisalo.net


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From: Chris Huff
Subject: Re: Radiosity scenes tinted?
Date: 10 Dec 2000 09:36:51
Message: <chrishuff-705491.09374410122000@news.povray.org>
In article <3A2FAB0A.D4918A9A@peak.edu.ee>, Margus Ramst 
<mar### [at] peakeduee> wrote:

> Well, in MegaPOV the default gray_threshold is 0, which  in most 
> cases makes the radiosity lighting look too saturated IMHO. In 
> regular POV the default is 0.5, but perhaps people still set it too 
> low to make the rad effects more conspicuous.

I think gray_threshold 0 is supposed to be the most realistic, it is a 
way to artificially limit the saturation of the color blending in the 
image.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><


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From: Margus Ramst
Subject: Re: Radiosity scenes tinted?
Date: 10 Dec 2000 11:15:27
Message: <3A33ACA9.9C226F3@peak.edu.ee>
Chris Huff wrote:
> 
> I think gray_threshold 0 is supposed to be the most realistic, it is a
> way to artificially limit the saturation of the color blending in the
> image.
> 

Perhaps, although it should also help counteract the effects of a limited number
of samples and recursion levels.
And for example radiosity lit "blue sky" outdoor scenes do tend to look
unrealistically blue IMO, so despite my limited knowledge of physics I must
assume there is some aspect of natural light behaviour not provided for here.

-- 
Margus Ramst

Personal e-mail: mar### [at] peakeduee
TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg
Home page http://www.hot.ee/margusrt


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From: Christoph Hormann
Subject: Re: Radiosity scenes tinted?
Date: 10 Dec 2000 11:41:58
Message: <3A33B241.3AE39D72@gmx.de>
Margus Ramst wrote:
> 
> And for example radiosity lit "blue sky" outdoor scenes do tend to look
> unrealistically blue IMO, so despite my limited knowledge of physics I must
> assume there is some aspect of natural light behaviour not provided for here.
> 

It's probably right that a blue sphere/sky_sphere is not a good physical
representation of a real sky.  NTL, don't forget that the sunlight is
usually far from being 'white' so there is some kind of compensation.  

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: ingo
Subject: Re: Radiosity scenes tinted?
Date: 10 Dec 2000 11:46:40
Message: <Xns9006BCC6Fseed7@povray.org>
Margus Ramst wrote:

>And for example radiosity lit "blue sky" outdoor scenes do tend to look
>unrealistically blue IMO, so despite my limited knowledge of physics I
>must assume there is some aspect of natural light behaviour not
>provided for here. 
>

In the real world there is no direct "colour-bleeding" from the blue sky. 
It where nice if it was possible to switch off the lolour of the bleeding 
from the "sky_sphere" in POV.

Photorealism: these blue pictures look as if an outdoor scene was 
photographed with a film suitable for artificial light.


Ingo

-- 
Photography: http://members.home.nl/ingoogni/
Pov-Ray    : http://members.home.nl/seed7/


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From: Chris Huff
Subject: Re: Radiosity scenes tinted?
Date: 10 Dec 2000 13:18:10
Message: <chrishuff-09094A.13190210122000@news.povray.org>
In article <3A3### [at] peakeduee>, Margus Ramst 
<mar### [at] peakeduee> wrote:

> Perhaps, although it should also help counteract the effects of a 
> limited number of samples and recursion levels.

This is true for some cases...


> And for example radiosity lit "blue sky" outdoor scenes do tend to look
> unrealistically blue IMO,

The human eye can compensate for color casts...try messing with the 
color temperature of your monitor, for example. At first it will look 
red or blue, but after a while it looks white again. POV doesn't do 
this, it simulates the effect of a "perfect" film camera. If someone did 
a post_process filter to simulate different types of film, you could set 
it up to use an outdoor film and lessen that effect while still using 
accurate radiosity settings.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><


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From: Chris Huff
Subject: Re: Radiosity scenes tinted?
Date: 10 Dec 2000 13:20:16
Message: <chrishuff-9B9F56.13210910122000@news.povray.org>
In article <Xns### [at] povrayorg>, ing### [at] homenl (ingo) 
wrote:

> In the real world there is no direct "colour-bleeding" from the blue sky. 

I believe you are mistaken...most of the illumination in the shade comes 
from scattered light. And things lit with sky light *do* have a blue 
cast, but your eyes usually adjust to it.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><


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