POV-Ray : Newsgroups : povray.general : Scattering media on a white background? Server Time
5 Aug 2024 08:19:08 EDT (-0400)
  Scattering media on a white background? (Message 1 to 8 of 8)  
From: Shay
Subject: Scattering media on a white background?
Date: 11 Nov 2002 11:37:35
Message: <3dcfdccf@news.povray.org>
Is there a combination of settings which makes this possible?

 -Shay


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From: ingo
Subject: Re: Scattering media on a white background?
Date: 11 Nov 2002 12:24:18
Message: <Xns92C3BC15D86CCseed7@povray.org>
in news:3dcfdccf@news.povray.org Shay wrote:

> Is there a combination of settings which makes this possible?
> 
> 

play with the extinction value or ad some absorbing media.

Ingo


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From: Christopher James Huff
Subject: Re: Scattering media on a white background?
Date: 11 Nov 2002 12:29:29
Message: <chrishuff-A6C486.12291411112002@netplex.aussie.org>
In article <3dcfdccf@news.povray.org>, "Shay" <sah### [at] simcopartscom> 
wrote:

> Is there a combination of settings which makes this possible?

Yes.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


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From: Christopher James Huff
Subject: Re: Scattering media on a white background?
Date: 11 Nov 2002 12:34:00
Message: <chrishuff-CF9C15.12334511112002@netplex.aussie.org>
In article <chr### [at] netplexaussieorg>,
 Christopher James Huff <chr### [at] maccom> wrote:

> Yes.

Scattering media works fine on a white background. You need to give more 
information about what you are doing to get a more detailed answer. You 
do need a non-0 value for extinction, maybe you set it to 0 for some 
reason. Or were you intending to ask about emitting media? In that case, 
add an absorbing media with a gray color or 1 - the emission color.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


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From: Shay
Subject: Re: Scattering media on a white background?
Date: 11 Nov 2002 14:45:25
Message: <3dd008d5$1@news.povray.org>
Christopher James Huff <chr### [at] maccom> wrote in message
news:chr### [at] netplexaussieorg...

What I am trying to do is give the appearance of light emanating from the
center of a partially covered sphere. What I have now is my continent model
from the last IRTC round in a group with a light source to light it from the
outside. I then have a second light source in the center of the globe and a
spherical media container filled with scattering media.

The effect of light being filtered by the continent model is perfect on a
black background, but I have not been able to make the scattering visible on
a white background. I am trying to make a quick picture for a holiday card,
so I'm looking for any help with getting this project over as quickly as
possible.

Thank you,
-Shay


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From: Peter Popov
Subject: Re: Scattering media on a white background?
Date: 11 Nov 2002 15:27:48
Message: <aj40tu8q8v3thkvjdoivmvqe9g8t18e6e2@4ax.com>
On Mon, 11 Nov 2002 12:33:45 -0500, Christopher James Huff
<chr### [at] maccom> wrote:

>add an absorbing media with a gray color or 1 - the emission color.

No, that's not true. The absorbed color should be the opposite in hue,
but the same in brightness as the emitted one. Your suggestion would
add less absorption for brighter emission and vice versa, which is not
what is generally wanted.

There, we're even now :)


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


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From: Christopher James Huff
Subject: Re: Scattering media on a white background?
Date: 11 Nov 2002 16:04:14
Message: <chrishuff-A702A5.16035811112002@netplex.aussie.org>
In article <aj40tu8q8v3thkvjdoivmvqe9g8t18e6e2@4ax.com>,
 Peter Popov <pet### [at] vipbg> wrote:

> No, that's not true. The absorbed color should be the opposite in hue,
> but the same in brightness as the emitted one. Your suggestion would
> add less absorption for brighter emission and vice versa, which is not
> what is generally wanted.

There isn't really a "right" and "wrong" way...just rules of thumb that 
usually work. "Hue" is an artificial way of specifying an attribute of 
colors, there is no physical reason for emitting gasses to absorb light 
of the opposite hue. The colors being absorbed don't always match the 
color being emitted.

Actually, there is a "right" way, but it would require patching POV to 
addjust the dynamic range. The beams of light are brighter than the 
background, but the background is "white".


> There, we're even now :)

Heh, OK...

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


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From: Christopher James Huff
Subject: Re: Scattering media on a white background?
Date: 11 Nov 2002 16:12:38
Message: <chrishuff-BA7A56.16122311112002@netplex.aussie.org>
In article <3dd008d5$1@news.povray.org>, "Shay" <sah### [at] simcopartscom> 
wrote:

> The effect of light being filtered by the continent model is perfect on a
> black background, but I have not been able to make the scattering visible on
> a white background. I am trying to make a quick picture for a holiday card,
> so I'm looking for any help with getting this project over as quickly as
> possible.

The beams are visible because they are brighter, right? Just use a 
dimmer background then. You can't get whiter than white. I'm not sure 
what you want white beams on a white background to look like...kind of 
like a polar bear in a snowstorm. If the beams are colored...well, you 
still have them being added to a 100% white background. Absorbing or 
extinction will make the beams visible by blocking the background...not 
white any more. The dynamic range patches floating around recently might 
be able to do what you want, otherwise you will have to post process the 
image.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


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