I found something on the web
(http://www.eg.org/EG/CGF/Volume12/issue3/v12i3pp201-210.pdf) and I'm
curious if the "Schlick phase function" would be of any use for POV-Ray's
media algorithms. Whenever I read something like "much faster to compute" I
get greedy heheheh.

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In article <3e95a16d@news.povray.org>,
 "Apache" <apa### [at] yahoocom> wrote:

> I found something on the web
> (http://www.eg.org/EG/CGF/Volume12/issue3/v12i3pp201-210.pdf) and I'm
> curious if the "Schlick phase function" would be of any use for POV-Ray's
> media algorithms. Whenever I read something like "much faster to compute" I
> get greedy heheheh.

Much faster than other methods that simulate multiple scattering. POV 
doesn't simulate multiple scattering, for speed reasons.

From what I can tell at a glance, this paper involves a preprocessing 
computation step similar to media photons or radiosity, followed by 
something similar to a standard raytracing media algorithm at render 
time. It is most likely quite a bit slower than the equivalent in POV, 
though more accurate.

-- 
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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in news:3e95a16d@news.povray.org Apache wrote:

> "Schlick phase function


On a side note, here are some of his other publications, some may be of 
interest:

http://dept-info.labri.u-bordeaux.fr/~schlick/publi.html

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If it's bsaed on preprocessing and the results are camera-location
independent, it would save time for animations wouldn't it?

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In article <3e984df8$1@news.povray.org>,
 "Apache" <apa### [at] yahoocom> wrote:

> If it's bsaed on preprocessing and the results are camera-location
> independent, it would save time for animations wouldn't it?

No. Most ways of simulating secondary scattering are *really slow*. This 
way is faster than those, but that doesn't mean it is faster than POV. 
I'd guess it is slower in the rendering pass alone, because it has to 
handle the data from the preprocessing pass as well as computing the 
first scattering data.

-- 
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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I've always been interested in the light-bleeding (a bit halo like) effect
that one can sometimes when there is something in the air (like dust or smog
or fog or whatever). At this moment the effect of media is only in direct
light. (Except for radiosity that takes media into account).
I would be very interested if media would be able to take radiosity or
scattered light into account! I won't mind if it's slow, I'm very patient!
(Most of my renders take more than days heheheh)

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In article <3e988cf3$1@news.povray.org>,
 "Apache" <apa### [at] yahoocom> wrote:

> I've always been interested in the light-bleeding (a bit halo like) effect
> that one can sometimes when there is something in the air (like dust or smog
> or fog or whatever). At this moment the effect of media is only in direct
> light. (Except for radiosity that takes media into account).

The effect is minimal in most situations, it is only really visible when 
you have a thin, bright beam or unusually dense media. One thing that 
might really benefit is fire/smoke, with the smoke reflecting light from 
the fire. The effect isn't useless, and will probably be implemented 
eventually, but it isn't extremely useful and ordinary single-scattering 
media is still slow.


> I would be very interested if media would be able to take radiosity or
> scattered light into account! I won't mind if it's slow, I'm very patient!
> (Most of my renders take more than days heheheh)

I thought you were interested in it for the increased speed...

Anyway, I've been looking at the paper a little more, and it looks like 
the Schlick function is a separate enhancement from the rendering 
algorithm, having a similar curve to the Henyey-Bernstein function while 
being simpler to compute. It might give some speed increase, though I 
would bet only a small one because the lighting calculations have a 
greater speed impact in my experience.

-- 
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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> I thought you were interested in it for the increased speed...
Initially, yes! But when things get slow, it must have something extra....
:)

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