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Does anyone know if this amazing lighting effect is being developed for
povray in any way?
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"ran102" <mon### [at] sti net> a écrit dans le message de news:
3f0f51e0$1@news.povray.org...
> Does anyone know if this amazing lighting effect is being developed
for
> povray in any way?
>
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.
G.
--
**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters
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On Sat, 12 Jul 2003 10:12:41 +0200, "Gilles Tran" <git### [at] wanadoofr>
wrote:
>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.
In addition to that, if your object seems fuzzy at the edges (might
happen no matter how dense the media inside it is), or if the shadow
is too soft and gives away the media inside, put an opaque
interior_texture to your object - best use the same as the exterior
texture sans the filter/transmit. For more detail and some examples,
see http://news.povray.org/povray.binaries.images/28847/ (shameless
plug :) )
Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG e-mail : pet### [at] tagpovrayorg
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Thanks, I will try that.
>
> Peter Popov ICQ : 15002700
> Personal e-mail : pet### [at] vipbg
> 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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"Tom & Lu Melly" <all### [at] tomandlucouk> a écrit dans le message de news:
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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"Tom & Lu Melly" <all### [at] tomandlucouk> a écrit dans le message de news:
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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Check out this picture of three glasses of milk
http://graphics.ucsd.edu/~henrik/images/imgs/milk.jpg. The one on the far
right has no subsurface scattering, and looks like thick paint. But the two
on the left do have this effect and replicate the look of milk almost
perfectly.
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In article <3f17203a$1@news.povray.org>, mon### [at] stinet says...
> Check out this picture of three glasses of milk
> http://graphics.ucsd.edu/~henrik/images/imgs/milk.jpg. The one on the far
> right has no subsurface scattering, and looks like thick paint. But the two
> on the left do have this effect and replicate the look of milk almost
> perfectly.
>
>
>
I have been thinking about this some. And media just won't do what is
really needed for this. What you need is something like:
texture {
pigment {Flesh}
Subsurface {
Pigment {
...
}
Scattering .5
Depth .1
}
}
Why? Because you can't get veins and things to show through properly.
Anything like that you mapped to it would end up on the surface, but you
want those sorts of things to be the 'subsurface' and have the light
bounce back from there. It 'may' be possible to make a model that has two
layers, one for the surface skin and a second for the subsurface and
stuff media in between them, but this is hardly efficient and imho is
outright impractical with a complex model. There is also the other
factor, in the case of something like the milk you are talking about, it
is literally impossible to make a media that is 'thick' enough (or my one
attempt to fiddle with it failed to produce such anyway) so as to mask
things behind it. Maybe in a very large container, but definitely not in
something small.
A real method to do this would be very useful.
--
void main () {
If Schrödingers_cat is alive
call functional_code()
else
call crash_windows();
}
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I have been able to with milk make it very thick. Changing the transparency
of the main pigment and also the brightness of the scattering pigment ( i
make it something like 4 or 5), I can produce milk that cannot be seen
through at all but has the scattering below the surface that makes it look
real. If you want I can post a picture of it on the pov binaries images.
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In article <3f186b18@news.povray.org>, mon### [at] stinet says...
> I have been able to with milk make it very thick. Changing the transparency
> of the main pigment and also the brightness of the scattering pigment ( i
> make it something like 4 or 5), I can produce milk that cannot be seen
> through at all but has the scattering below the surface that makes it look
> real. If you want I can post a picture of it on the pov binaries images.
>
>
>
Rather see the code. lol Having fiddled with trying to do something of
the sort a bit, I got quite annoyed. Though I suspect you are still not
doing what I meant. I.e. you are having the surface of the media
container define 'part' of the 'substance' of the media. This works, but
isn't quite what I was experimenting to achieve. It also doesn't solve
the other issue with having a real texture 'beneath' the layer in which
the scattering, or media, needs to be active. Thus it works great for
milk, but basically fails with something like skin. Which doesn't exactly
help me much in the long run. ;) lol
However, to give you an idea of what I was trying to manage in this case.
The concept was to take a sphere, fill it with the densest red colored
media I could, then shave the side of the sphere off (differencing a
transparent block from it). The expected result was a thick soupy
interior that significantly obscured the other side of the sphere and
made the inside 'seem' semi-solid. I suspect that part of the problem was
the sphere being way to small, but I also suspect that it is simply
impossible to make media 'thick' enough to obscure objects at relatively
short distances without resorting to something like what you seem to be
talking about doing for the milk. However, I could have simply screwed up
the settings. ;) I am pretty much flying blind here and experimenting
with something I never used before. lol
--
void main () {
If Schrödingers_cat is alive
call functional_code()
else
call crash_windows();
}
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Patrick Elliott wrote:
> I suspect that part of the problem was the sphere being way to small, but I also
suspect that it is simply
> impossible to make media 'thick' enough to obscure objects at relatively
> short distances without resorting to something like what you seem to be
> talking about doing for the milk.
You know, the 'scale' keyword works for media densities too...perhaps
that will help with making the relatively short distances less of a
problem.
--
Tim Cook
http://home.bellsouth.net/p/PWP-empyrean
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------
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In article <3f19b4f6@news.povray.org>, Tim Cook <z99### [at] bellsouthnet>
wrote:
> You know, the 'scale' keyword works for media densities too...perhaps
> that will help with making the relatively short distances less of a
> problem.
The scale keyword only scales the pattern. You have to scale the density
manually.
--
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 article <MPG.19835f5a3e611a0798983b@news.povray.org>,
Patrick Elliott <sha### [at] hotmailcom> wrote:
> I suspect that part of the problem was
> the sphere being way to small, but I also suspect that it is simply
> impossible to make media 'thick' enough to obscure objects at relatively
> short distances without resorting to something like what you seem to be
> talking about doing for the milk. However, I could have simply screwed up
> the settings. ;) I am pretty much flying blind here and experimenting
> with something I never used before. lol
To make it thicker, you just need to increase the density. To get the
same results at half the scale, you need to double the density. It
sounds like you think there is some limit to how dense you can make
media, or that high densities are somehow a "last resort".
--
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 article <cja### [at] netplexaussieorg>,
cja### [at] earthlinknet says...
> In article <MPG.19835f5a3e611a0798983b@news.povray.org>,
> Patrick Elliott <sha### [at] hotmailcom> wrote:
>
> > I suspect that part of the problem was
> > the sphere being way to small, but I also suspect that it is simply
> > impossible to make media 'thick' enough to obscure objects at relatively
> > short distances without resorting to something like what you seem to be
> > talking about doing for the milk. However, I could have simply screwed up
> > the settings. ;) I am pretty much flying blind here and experimenting
> > with something I never used before. lol
>
> To make it thicker, you just need to increase the density. To get the
> same results at half the scale, you need to double the density. It
> sounds like you think there is some limit to how dense you can make
> media, or that high densities are somehow a "last resort".
>
>
Umm. I am confused here.. Looking at the docs implies that density is a
color vector. I am a bit unclear how you make that more dense, nor does
increasing the size of this vector seem to produce a noticeable effect.
It is possible something about what I am doing is simply not allowing
media to be seen, but... Like I said, I haven't a clue what I am doing, I
just tried something and it doesn't seem to be doing what I expected (if
anything). :p
camera {
location <0.0000001,0,-200>
look_at <0,0,0>
}
light_source {
<0, 0, -130>
color rgb <1, 1, 1> // light's color
}
light_source {
<130, 0, -130>
color rgb <.5, .5, .5> // light's color
}
light_source {
<-130, 0, -130>
color rgb <.5, .5, .5> // light's color
}
difference {
sphere {<0,0,0>, 100
pigment {color rgb <1,0,0>}
hollow
interior {
media {
//absorption rgb <1,0,0>
//emission rgb <1,0,0>
intervals 1
variance 0
scattering {1, rgb <1,0,0> extinction 0}
density {
checker
density {rgb <1,0,0>}
density {rgb <1,1,0>}
}
}
}
}
box {<-110,-110,5>,<0,110,-100>
pigment {rgbt <1,1,1,1>}
}
rotate <0,-20,0>
//no_shadow
}
--
void main () {
If Schrödingers_cat is alive
call functional_code()
else
call crash_windows();
}
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In article <MPG.198496eefefa88b98983e@news.povray.org>,
Patrick Elliott <sha### [at] hotmailcom> wrote:
> Umm. I am confused here.. Looking at the docs implies that density is a
> color vector. I am a bit unclear how you make that more dense,
To put it in technical terms: use bigger numbers.
> nor does
> increasing the size of this vector seem to produce a noticeable effect.
It does.
> scattering {1, rgb <1,0,0> extinction 0}
You only scatter red light, green and blue are unaffected by this media
(though your pigment filters them out). When I'm doing an object that is
mainly colored by its interior, I use a pigment of rgbf 1. Yours filters
everything red. In addition, your extinction is set to 0, this media
won't impede light passing through it. And you don't have anything else
in your scene. I'm not really sure what effect you're after, you're
certainly not going to get anything like milk with that. Your density
pattern has so much fine detail that you are going to require a lot of
sampling to get decent results, even after scaling it up by 10.
--
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 article <cja### [at] netplexaussieorg>,
cja### [at] earthlinknet says...
> In article <MPG.198496eefefa88b98983e@news.povray.org>,
> Patrick Elliott <sha### [at] hotmailcom> wrote:
>
> > Umm. I am confused here.. Looking at the docs implies that density is a
> > color vector. I am a bit unclear how you make that more dense,
>
> To put it in technical terms: use bigger numbers.
>
>
> > nor does
> > increasing the size of this vector seem to produce a noticeable effect.
>
> It does.
>
>
> > scattering {1, rgb <1,0,0> extinction 0}
>
> You only scatter red light, green and blue are unaffected by this media
> (though your pigment filters them out). When I'm doing an object that is
> mainly colored by its interior, I use a pigment of rgbf 1. Yours filters
> everything red. In addition, your extinction is set to 0, this media
> won't impede light passing through it. And you don't have anything else
> in your scene. I'm not really sure what effect you're after, you're
> certainly not going to get anything like milk with that. Your density
> pattern has so much fine detail that you are going to require a lot of
> sampling to get decent results, even after scaling it up by 10.
>
>
Hmm.. Wasn't thinking about what was actually being scattered there.
Probably why absorption didn't work either when I tried it that way. lol
As for the effect.. I am not looking for milk, etc. Just really dense
media. I used the checker pattern to add some variance to it when I
realized something wasn't working and figured a pattern could tell me if
it was working at all. The idea was to try to see if I could make the
media solid enough to make it seem as though the inside was nearly solid,
by having the media fill it in, instead of simply CSGing a box with the
same color as the sphere. Stupid, but... lol Probably should have looked
at some real examples first and worked from there. ;)
Basically, I wanted it so thick that the back shadow nearly disappears
and the media seemed to be part of the sphere itself, not just something
that kind of floated in it. At this point I am about ready to scrap the
entire experiment, since I seem to flat out not get how this feature
works. lol
--
void main () {
If Schrödingers_cat is alive
call functional_code()
else
call crash_windows();
}
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