POV-Ray: Newsgroups: povray.advanced-users: Scattering media not sampled properly?

POV-Ray : Newsgroups : povray.advanced-users : Scattering media not sampled properly?		Server Time 29 Oct 2024 22:47:29 EDT (-0400)

From: clipka
Subject: Scattering media not sampled properly?
Date: 24 Mar 2009 22:05:01
Message: <web.49c990d587fb1a98ee2312a30@news.povray.org>

I may be mistaken, but in experimenting with scattering media, it seems to me
that sampling method 3 fails to properly attenuate the light scattered to the
observer, leading to what I think is overly bright media when e.g. viewing a
media-based ground fog at a shallow angle.

Another thing that worries me is that the illumination of scattering media does
not seem to take into account extinction effects from the very same media - or
at least I wasn't able to dig up the code that does it.

Anyone can confirm / disprove this?

I'll try to draft some test scenes for the two issues.

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From: Alain
Subject: Re: Scattering media not sampled properly?
Date: 24 Mar 2009 23:39:46
Message: <49c9a782$1@news.povray.org>

clipka nous illumina en ce 2009-03-24 22:03 -->
> I may be mistaken, but in experimenting with scattering media, it seems to me
> that sampling method 3 fails to properly attenuate the light scattered to the
> observer, leading to what I think is overly bright media when e.g. viewing a
> media-based ground fog at a shallow angle.
> 
> Another thing that worries me is that the illumination of scattering media does
> not seem to take into account extinction effects from the very same media - or
> at least I wasn't able to dig up the code that does it.
> 
> Anyone can confirm / disprove this?
> 
> I'll try to draft some test scenes for the two issues.
> 
> 
> 
Any ray that goes trough the media is affected by that media for it's full path 
trough that media.
So, there is some extinction between a meam of light in the media and the 
observer. Maybe it's just not at the strenght that you are expecting it to show.

Also, you may not have enough samples. Try doubling the number of samples. Leave 
intervals to it's default: just don't use intervals.

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you look at real clouds and 
criticise their media and radiosity settings.
Tom Melly

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From: Kenneth
Subject: Re: Scattering media not sampled properly?
Date: 25 Mar 2009 00:40:01
Message: <web.49c9b54798c2dd72f50167bc0@news.povray.org>

"clipka" <nomail@nomail> wrote:

> I'll try to draft some test scenes for the two issues.

Yes, please do. I'm curious. (I *think* I've seen odd effects with scattering
media myself, which I've never been able to pin down.)

KW

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