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Thanks, I will try that.
>
> Peter Popov ICQ : 15002700
> Personal e-mail : pet### [at] vip bg
> TAG e-mail : pet### [at] tagpovrayorg
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> Does anyone know if this amazing lighting effect is being developed
for
> povray in any way?
Am I the only one who never could tell the difference between something with
subsurface scattering and something without it?
I can see the difference when dense media is used within an object, but is
this really the same exact effect? And why would human skin have it? *My*
skin certainly isn't very transparent.
- Slime
[ http://www.slimeland.com/ ]
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Okay, this is a very good question. Many people don't spot it right off, so
here is a simple test you can do that will show you how it looks and what it
does.
Do you own a red laser pointer? Using a dark card, go in a darkened room
and place the card against your skin, edgewise. Now, shine the laser pointer on
the skin on the other side of the card- not the part of the skin you are looking
at.
When you see the red, diffuse glow under the card, you are seeing subsurface
scattering. But you probably knew that. In looking at the surface of, say, a
mannequin, you will see that the shadows are very hard and there is no
subsurface scattering. With real flesh, there is considerable softening of the
shadows and a really significant amount of light diffusion beneath the surface.
Skin is actually transparent to a number of frequencies, but in visible
light, it tends to be right in the red end of the spectrum. If you model skin
with an internal red scattering, or a red diffuse medium, it looks far more
natural when light falls on it. Instead of that blocky, plastic look, it has
the depth and softness that we expect.
Seeing some of your renders in this group, I know that you are aware of how
the little details make or break an image. This is one of those things that
really makes people look realistic.
Oh, I tend to use a pale orange sort of color when playing with skin
subsurface scattering. Use white light for the experiment above and you will
see that this is the dominant color that appears to the human eye.
Cheers!
Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
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"Gilles Tran" <git### [at] wanadoofr> wrote in message
news:3f0fc2ff@news.povray.org...
>
>
> Filling an object with very dense scattering media makes a good subsurface
> scattering effect. The texture of the object must be part transparent so
> that both the surface pigment and the media inside are visible.
Do you have any sample-code of this? I'm struggling for this at the moment,
and rather working in the dark.
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3f144f57@news.povray.org...
> Do you have any sample-code of this? I'm struggling for this at the
moment,
> and rather working in the dark.
Try the code below. Left sphere is with subsurface scattering.
Note that it shows one problem I had with the ISS image when I used this on
the kid's arm, which is that the dark (densest) parts tend to be quite black
and do not react to radiosity. The only solution I found is by using
emission, which caused other problems and then I ran out of testing time.
It's also a problem with clouds, but it can be camouflaged by fog... I guess
that until we get real blurred transluscency there's no permanent
solution... unless I missed something obvious that is.
global_settings{
assumed_gamma 1
radiosity{media on}
}
camera {
location <0,1,-4>
direction z
right x*image_width/image_height
look_at y
}
sphere{0,1
texture{
pigment{rgbf <1,0.6,0.2,1>}
finish{ambient 0 diffuse 1 specular 0.2 roughness 1/200 }
}
hollow
interior{
media{
scattering {1 rgb 4}
}
}
translate y
translate -x*1.1
}
sphere{0,1
texture{
pigment{rgb <1,0.6,0.2>}
finish{ambient 0 diffuse 1 specular 0.2 roughness 1/200}
}
translate y
translate x*1.1
}
plane{y,0 texture{pigment{rgb 1} finish{ambient 0 diffuse 1}}}
light_source {0 color rgb 1 translate <-1,1,1>*1000}
--
**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters
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"Gilles Tran" <git### [at] wanadoofr> wrote in message
news:3f145c58@news.povray.org...
>
Many thanks. Excellent service. This newsgroup looks ripe for privatisation.
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3f14673f@news.povray.org...
> "Gilles Tran" <git### [at] wanadoofr> wrote in message
> news:3f145c58@news.povray.org...
> >
>
> Many thanks. Excellent service. This newsgroup looks ripe for
privatisation.
True enough, I can't wait to have our first POV-Ray accidents once the
development is subcontracted to the lowest bidders/highest bribers using
temporary and expandable workers with prior expertise in fruit picking ;)
G.
--
**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters
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On Wed, 16 Jul 2003 00:40:05 +0200, "Gilles Tran" <git### [at] wanadoofr> wrote:
>> Many thanks. Excellent service. This newsgroup looks ripe for
>privatisation.
>
>True enough, I can't wait to have our first POV-Ray accidents once the
>development is subcontracted to the lowest bidders/highest bribers using
>temporary and expandable workers with prior expertise in fruit picking ;)
>
That told him :-}
Regards
Stephen
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"Gilles Tran" <git### [at] wanadoofr> wrote in message
news:3f145c58@news.povray.org...
> Try the code below. Left sphere is with subsurface scattering.
> Note that it shows one problem I had with the ISS image when I used this
on
> the kid's arm, which is that the dark (densest) parts tend to be quite
black
> and do not react to radiosity.
So to compensate the lack of radiosity (on this object), would you just use
a light_group to give it ambient light?
...Chambers
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In article <3f124882$1@news.povray.org>, "Slime" <slm### [at] slimelandcom>
wrote:
> I can see the difference when dense media is used within an object, but is
> this really the same exact effect?
Not exactly the same effect, but very close. POV media doesn't simulate
secondary scattering...a bright light scatters light to the camera, but
not to other media. Something like photons may make this possible, or
have scattering media use radiosity, but you can guess at the CPU
requirements...anyway, for most purposes, media will work fine. Since
subsurface scattering is usually limited to the near-surface, you might
get render time and quality improvements by using an opaque core with a
media shell.
> And why would human skin have it? *My*
> skin certainly isn't very transparent.
Your skin is perfectly opaque? You should probably see a doctor about
that...
Flesh is normally fairly translucent. You can see veins under it, softer
terminator lines on shadows, and reddish coloration of light filtering
through it. There are images demonstrating this pretty well...an image
without subsurface scattering looks like the skin is coated with a layer
of paint when compared to one with subsurface scattering. Or like
really, really thick makeup.
--
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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