I'm looking for a (free) renderer that does realistic subsurface scattering,
using physical material parameters as input (i.e. absorption and scattering
coefficients) - or a way to do it in POV. Rendering times don't matter, even if
it takes days to render a simple wax sphere on a checkered plane. Main
prerequisite is high physical accuracy.

I had hoped for a combination of scattering and absorbing media in POV to do the
job, but it doesn't seem to work with real physical material properties - unless
someone happens to know a reliable way to convert those properties to POV media
parameters.

The parameters I have available - aside from index of refraction - are
"absorption coefficients" and "reduced scattering coefficients" for red, green
and blue light respectively (computed from measurements under the simplifying
assumption that the "phase function" is isotropic).

Any ideas?

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clipka <nomail@nomail> wrote:
> I'm looking for a (free) renderer that does realistic subsurface scattering,

  Something like this?

http://www.luxrender.net/gallery/main.php?g2_itemId=2294&g2_imageViewsIndex=1

-- 
                                                          - Warp

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Warp <war### [at] tagpovrayorg> wrote:
> > I'm looking for a (free) renderer that does realistic subsurface scattering,
>
>   Something like this?
>
> http://www.luxrender.net/gallery/main.php?g2_itemId=2294&g2_imageViewsIndex=1

Don't know - it's difficult to tell from a shot whether the materials were
modelled based on actual measured physical properties, or just diligently
tweaked until they looked just right, isn'it it?

I'm after a renderer with a realistic - not only convincing - subsurface
scattering model. And I'm after a renderer, not just some shots.

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http://aqsis.org/ Renderman Compliant, so you should be able to make about 
whatever you want.
http://www.indigorenderer.com/joomla/  Indigo rocks too.
http://www.indigorenderer.com/joomla/component/option,com_gallery2/Itemid,26/?g2_itemId=6441

ian

"clipka" <nomail@nomail> wrote in message 
news:web.49aee7c45c51f8d126f6761f0@news.povray.org...
> I'm looking for a (free) renderer that does realistic subsurface 
> scattering,
> using physical material parameters as input (i.e. absorption and 
> scattering
> coefficients) - or a way to do it in POV. Rendering times don't matter, 
> even if
> it takes days to render a simple wax sphere on a checkered plane. Main
> prerequisite is high physical accuracy.
>
> I had hoped for a combination of scattering and absorbing media in POV to 
> do the
> job, but it doesn't seem to work with real physical material properties - 
> unless
> someone happens to know a reliable way to convert those properties to POV 
> media
> parameters.
>
> The parameters I have available - aside from index of refraction - are
> "absorption coefficients" and "reduced scattering coefficients" for red, 
> green
> and blue light respectively (computed from measurements under the 
> simplifying
> assumption that the "phase function" is isotropic).
>
> Any ideas?
>
>
>
>

Post a reply to this message

"clipka" <nomail@nomail> wrote:
> Warp <war### [at] tagpovrayorg> wrote:
> > > I'm looking for a (free) renderer that does realistic subsurface scattering,
> >
> >   Something like this?
> >
> > http://www.luxrender.net/gallery/main.php?g2_itemId=2294&g2_imageViewsIndex=1
>
> Don't know - it's difficult to tell from a shot whether the materials were
> modelled based on actual measured physical properties, or just diligently
> tweaked until they looked just right, isn'it it?
>
> I'm after a renderer with a realistic - not only convincing - subsurface
> scattering model. And I'm after a renderer, not just some shots.

This is the thread for that image:
http://www.luxrender.net/forum/viewtopic.php?f=14&t=1431

It uses a predefined material with a few parameters that don't seem to bear much
resemblance to any accurate physical properties.

Aqsis, being a Renderman system, should be even farther away from physical
correctness than unbiased renderers like Lux and Indigo.

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"nemesis" <nam### [at] gmailcom> wrote in message 
news:web.49af023180e98aa0773c9a3e0@news.povray.org...
> Aqsis, being a Renderman system, should be even farther away from physical
> correctness than unbiased renderers like Lux and Indigo.
>

My understanding of renderman compliant renderers was that you can program 
shaders for nearly any behavior, is this incorrect?

ian

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"[GDS|Entropy]" <gds### [at] hotmailcom> wrote:
> "nemesis" <nam### [at] gmailcom> wrote in message
> news:web.49af023180e98aa0773c9a3e0@news.povray.org...
> > Aqsis, being a Renderman system, should be even farther away from physical
> > correctness than unbiased renderers like Lux and Indigo.
> >
>
> My understanding of renderman compliant renderers was that you can program
> shaders for nearly any behavior, is this incorrect?

Yes, but how does that integrate with a biased lighting model?

Post a reply to this message

"[GDS|Entropy]" <gds### [at] hotmailcom> wrote:
> My understanding of renderman compliant renderers was that you can program
> shaders for nearly any behavior, is this incorrect?

Renderman is a biased renderer, meaning it is not a good way to achieve the
physical accuracy clipka seeks.  It may technically be possible to implement
it, but it's certainly not a good idea.

http://www.cgafaq.info/wiki/Bias_in_rendering

 - Ricky

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I gotcha.
Thanks for the info. ;-D

ian


"triple_r" <nomail@nomail> wrote in message 
news:web.49af4ce980e98aa063a1b7c30@news.povray.org...
> "[GDS|Entropy]" <gds### [at] hotmailcom> wrote:
>> My understanding of renderman compliant renderers was that you can 
>> program
>> shaders for nearly any behavior, is this incorrect?
>
> Renderman is a biased renderer, meaning it is not a good way to achieve 
> the
> physical accuracy clipka seeks.  It may technically be possible to 
> implement
> it, but it's certainly not a good idea.
>
> http://www.cgafaq.info/wiki/Bias_in_rendering
>
> - Ricky
>
>
>
>
>

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"clipka" <nomail@nomail> wrote:
> I'm looking for a (free) renderer that does realistic subsurface scattering,
> using physical material parameters as input (i.e. absorption and scattering
> coefficients) - or a way to do it in POV. Rendering times don't matter, even if
> it takes days to render a simple wax sphere on a checkered plane. Main
> prerequisite is high physical accuracy.
>
> I had hoped for a combination of scattering and absorbing media in POV to do the
> job, but it doesn't seem to work with real physical material properties - unless
> someone happens to know a reliable way to convert those properties to POV media
> parameters.
>
> The parameters I have available - aside from index of refraction - are
> "absorption coefficients" and "reduced scattering coefficients" for red, green
> and blue light respectively (computed from measurements under the simplifying
> assumption that the "phase function" is isotropic).
>
> Any ideas?

Clipka a Sam Benge process may be useful?:
http://news.povray.org/489cc386%40news.povray.org

Clipka, sorry if I did not fully understand your question. :-)

(
POV info:
For those who do not know, I remember that Mr. Cason is working on:
http://news.povray.org/49688faa%40news.povray.org
)

--
Carlo

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