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Here is a test of a skin shader for Vahur Krouverk's POVMan patch. As
the shader patch doesn't (yet) support image_maps, the shader pigment is
added as a layered texture, which works pretty well. Vahur was kind
enough to post the shader code yesterday in p.unofficial.patches.
The first pic uses the shader, that creates a skin-like sheen, while the
second uses a regular finish (if the images appear on reverse order,
look at the small text on the right to be sure). Both use radiosity and
an area_light. Each takes 45 minutes to render on a PIII 733.
Other image details are quite irrelevant, since it's mostly premade
stuff : background is a blurred photograph, model and model textures are
Zygote's Victoria, hair and hair texture are from Alexander Nesterenko's
site. I added a slight normal to simulate the skin bumps. Lots of things
there would need fixing, like the strange shadow under Vicky's jaw, the
painted highlights on the hair, the skin bumps, the dull eyes and usual
lack of expressivity of Poser models.
Gilles Tran
The book of beginnings, Povray gallery
http://www.mediaport.net/Artichaud/Tran/gtran.en.html
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Attachments:
Download 'gtwshader.jpg' (36 KB)
Download 'gtnoshader.jpg' (36 KB)
Preview of image 'gtwshader.jpg'
![gtwshader.jpg](/povray.binaries.images/attachment/%3C3A3125D6.6DC4DD32%40inapg.inra.fr%3E/gtwshader.jpg?preview=1)
Preview of image 'gtnoshader.jpg'
![gtnoshader.jpg](/povray.binaries.images/attachment/%3C3A3125D6.6DC4DD32%40inapg.inra.fr%3E/gtnoshader.jpg?preview=1)
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Of course the shader version looks better, but i wonder whether it would
be possible to tweak the finish settings of the regular version to come
nearer to the first one. There does not seem to be much difference apart
from the intensity of the highlights.
Christoph
--
Christoph Hormann <chr### [at] gmx de>
IsoWood include, radiosity tutorial, TransSkin and other
things on: http://www.schunter.etc.tu-bs.de/~chris/
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>The first pic uses the shader, that creates a skin-like sheen, while the
>second uses a regular finish (if the images appear on reverse order,
Nice! What do you mean by regular finish?
sig
--
ICQ 74734588
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Fascinating... the normal I don't like. The rest is perfect.
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Waaouuuuu...
I'm in love :-)
About the shader, it seems to simulate the way microscopic hair
catch the light at the skin's surface in such situations.. does it ?
It seems that she have a little cast
(je suis pas certain de la traduction : je veux dire qu'elle louche !)
as if the eyes were spatially parallel, which they shouldn't be.
The eyes must "point" at the same (far) direction (look the same point),
to look good, from my experience.
Fabien.
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On Fri, 08 Dec 2000 19:17:58 +0100 Gilles Tran wrote:
>Here is a test of a skin shader for Vahur Krouverk's POVMan patch.
<snip..>
Interesting test images, Gilles. If you run more such tests of Vahur's
POVMan patch, please share it with us. It gives us insight into both the
strengths and limitations of the patch.
--
Alan - ako### [at] povray org - a k o n g <at> p o v r a y <dot> o r g
http://www.povray.org - Home of the Persistence of Vision Ray Tracer
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Christoph Hormann wrote:
> Of course the shader version looks better, but i wonder whether it would
> be possible to tweak the finish settings of the regular version to come
> nearer to the first one. There does not seem to be much difference apart
> from the intensity of the highlights.
At least I haven't been able to reproduce it with usual finish statements.
As a long time Poser user, I had always found that skin textures was badly
rendered in Povray (and in other renderers) : it's not a problem of
highlight intensity. My tests tried to show off the "silver lining"
characteristic of backlit or side-lit skin. Regular smaller highlights will
just give you a shiny aspect.
The skin shader is "based on phenomenological information about skin
reflectance" (quoting the doc). It takes into account that real skin is made
of layers with different scattering properties. The shader considers that
skin is made of a top oily glossy layer and of a subsurface. Note that I
still have to go deeper into that to understand it...
G.
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Sigmund Kyrre Aas wrote:
> >The first pic uses the shader, that creates a skin-like sheen, while the
> >second uses a regular finish (if the images appear on reverse order,
>
> Nice! What do you mean by regular finish?
Here it's just :
finish{ambient 0 diffuse 1 specular 0.03 roughness 0.01}
I usually change these parameters according to the scene the character is in.
Using the shader method is just adding a top layer :
texture{UsualSkinTexture}texture{SheenTexture}
G.
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Fabien Mosen wrote:
> Waaouuuuu...
> I'm in love :-)
Look in the French-speaking newsgroup for another take on Victoria :-)
> It seems that she have a little cast as if the eyes were spatially
> parallel, which they shouldn't be.
To be frank, I have trouble controlling this (and the iris size) so the
angles are different for the left and right eyes. For some reason the aspect
seems to change according to the angle of vision, but I'll look more
closely.
G.
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Gilles Tran wrote:
>
> At least I haven't been able to reproduce it with usual finish statements.
> As a long time Poser user, I had always found that skin textures was badly
> rendered in Povray (and in other renderers) : it's not a problem of
> highlight intensity. My tests tried to show off the "silver lining"
> characteristic of backlit or side-lit skin. Regular smaller highlights will
> just give you a shiny aspect.
>
I didn't mean to decrease roughness, but to decrease the specular
component. I'm not sure whether this will help much, but i'm quite sure
that it can be at least slightly better. I think i now understand what
you mean by "silver lining", it is probably really problematic with
conventional finish.
I never seriously tried megapov's 'blinn' highlights, but it's surely also
worth trying.
Christoph
--
Christoph Hormann <chr### [at] gmx de>
IsoWood include, radiosity tutorial, TransSkin and other
things on: http://www.schunter.etc.tu-bs.de/~chris/
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