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From: Ammar
Subject: Rayleigh Scattering in Pov Ray
Date: 26 Apr 2000 07:29:29
Message: <3906d319@news.povray.org>
Hello All

Is there anyone out there who could provide me with some sort of code for
implementing Rayleigh scattering equation.

I a currently trying to implement a model for the atmosphere, but I need the
right from of scattering equation for this to work.

Thanks.

Ammar


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From: Chris Huff
Subject: Re: Rayleigh Scattering in Pov Ray
Date: 26 Apr 2000 09:28:32
Message: <chrishuff_99-849F96.08313226042000@news.povray.org>
In article <3906d319@news.povray.org>, "Ammar" <a.a### [at] ueaacuk> 
wrote:

> Is there anyone out there who could provide me with some sort of code for
> implementing Rayleigh scattering equation.
> 
> I a currently trying to implement a model for the atmosphere, but I 
> need the right from of scattering equation for this to work.

There is already Rayleigh scattering...scattering media type 3. Are you 
trying to implement wavelength dependant Rayleigh scattering?

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/


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From: Peter Popov
Subject: Re: Rayleigh Scattering in Pov Ray
Date: 26 Apr 2000 15:36:25
Message: <oogegscuvkcuspnpa61c54tg09h153h4kg@4ax.com>
On Wed, 26 Apr 2000 08:31:32 -0500, Chris Huff
<chr### [at] yahoocom> wrote:

>There is already Rayleigh scattering...scattering media type 3. Are you 
>trying to implement wavelength dependant Rayleigh scattering?

Because if you are, too bad, as you currently can't. IIRC a patch is
being to implement wavelength dependant Rayleigh scattering but I
don't know what its progress is.

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


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From: Chris Huff
Subject: Re: Rayleigh Scattering in Pov Ray
Date: 26 Apr 2000 16:21:53
Message: <chrishuff_99-B105FE.15245326042000@news.povray.org>
In article <oogegscuvkcuspnpa61c54tg09h153h4kg@4ax.com>, Peter Popov 
<pet### [at] usanet> wrote:

> On Wed, 26 Apr 2000 08:31:32 -0500, Chris Huff
> <chr### [at] yahoocom> wrote:
> 
> >There is already Rayleigh scattering...scattering media type 3. Are you 
> >trying to implement wavelength dependant Rayleigh scattering?
> 
> Because if you are, too bad, as you currently can't. IIRC a patch is
> being to implement wavelength dependant Rayleigh scattering but I
> don't know what its progress is.

I had the impression Ammar was trying to write a patch which adds 
Rayleigh scattering, which is evidently not the case. Also, Rayleigh 
scattering is media type 4, not 3 as the documentation states.

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/


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From: Mark Wagner
Subject: Re: Rayleigh Scattering in Pov Ray
Date: 27 Apr 2000 01:13:24
Message: <3907cc74$1@news.povray.org>
Peter Popov wrote in message ...
>On Wed, 26 Apr 2000 08:31:32 -0500, Chris Huff
><chr### [at] yahoocom> wrote:
>
>>There is already Rayleigh scattering...scattering media type 3. Are you
>>trying to implement wavelength dependant Rayleigh scattering?
>
>Because if you are, too bad, as you currently can't. IIRC a patch is
>being to implement wavelength dependant Rayleigh scattering but I
>don't know what its progress is.


Current progress is that it is almost complete.  However, I'm running into
the problem of oversaturation of colors near the horizon.  Consequently, the
image looks just fine -- until you get to the horizon.  At that point, the
sky turns white.

I'm waiting for the "film effect" post-processing to be implemented to see
if this will fix the problem.  If people want me to, by next Thursday I
could release a version that doesn't have this problem fixed.

Mark


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From: Bob Hughes
Subject: Re: Rayleigh Scattering in Pov Ray
Date: 27 Apr 2000 14:14:32
Message: <39088388@news.povray.org>
"Mark Wagner" <mar### [at] gtenet> wrote in message
news:3907cc74$1@news.povray.org...
|
|  If people want me to, by next Thursday I
| could release a version that doesn't have this problem fixed.

Well, I for one won't stop you from doing so.

Bob


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From: Peter Popov
Subject: Re: Rayleigh Scattering in Pov Ray
Date: 28 Apr 2000 02:56:34
Message: <7m8igs024ej0nm5t62hpv4r1ob538qv9bt@4ax.com>
On Thu, 27 Apr 2000 01:15:06 -0400, "Mark Wagner"
<mar### [at] gtenet> wrote:

>Current progress is that it is almost complete.  However, I'm running into
>the problem of oversaturation of colors near the horizon.  Consequently, the
>image looks just fine -- until you get to the horizon.  At that point, the
>sky turns white.

Well, maybe you could fake it by decreasing brightness by an
exponential factor. Not quite realistic, I guess, but it will look as
expected and that what usually counts.

>I'm waiting for the "film effect" post-processing to be implemented to see
>if this will fix the problem.  If people want me to, by next Thursday I
>could release a version that doesn't have this problem fixed.

This would basically take the same approach, right? I mean, applying a
nonlinear curve to input/output brightness to desaturate the upper
levels.


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


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From: Mark Wagner
Subject: Re: Rayleigh Scattering in Pov Ray
Date: 29 Apr 2000 01:49:27
Message: <390a77e7@news.povray.org>
Peter Popov wrote in message <7m8igs024ej0nm5t62hpv4r1ob538qv9bt@4ax.com>...
>On Thu, 27 Apr 2000 01:15:06 -0400, "Mark Wagner"
><mar### [at] gtenet> wrote:
>
>>Current progress is that it is almost complete.  However, I'm running into
>>the problem of oversaturation of colors near the horizon.  Consequently,
the
>>image looks just fine -- until you get to the horizon.  At that point, the
>>sky turns white.
>
>Well, maybe you could fake it by decreasing brightness by an
>exponential factor. Not quite realistic, I guess, but it will look as
>expected and that what usually counts.


The problem is figuring out how to do this while computing the media.  It
would be much easier to do this after the image is rendered.

>>I'm waiting for the "film effect" post-processing to be implemented to see
>>if this will fix the problem.  If people want me to, by next Thursday I
>>could release a version that doesn't have this problem fixed.
>
>This would basically take the same approach, right? I mean, applying a
>nonlinear curve to input/output brightness to desaturate the upper
>levels.


Yes, but as I said above, it is easier to implement.

Mark


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