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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] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other
things on: http://www.schunter.etc.tu-bs.de/~chris/
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Gilles Tran wrote:
>
This skin shader seems to add more realism to the image than usual
finish. Now I have more interest in developing next version of shader
patch :-)
If someone is more interested in skin shader, then number of comparative
renderings were performed and posted in c.g.r.r. newsgroup (last r
stands for RenderMan and renderings were performed with RenderMan
compatible renderers, mostly BMRT, IIRC). Name of one of the threads was
"Skin Shaders. Any suggestions." from August/September this year. There
was posted number of links for theory of such shaders as well. Here is
excerpt from Matt Pharr's post:
====================================
You might want to start by reading Pat Hanrahan and Wolfgang Krueger's
paper, "Reflection from Layered Surfaces Due to Subsurface Scattering",
http://graphics.stanford.EDU/papers/subsurface/. In addition to lots of
nice theory and real-world data about scattering from biological stuff
like
skin and leaves, there's a lot of useful phenomenological information
about
how skin scatters light. If you liked that paper, you might also want
to
check out http://graphics.stanford.edu/papers/scatteringeqns, which
gives
some more efficient ways of computing scattering like this.
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Someone said " ...blinn highlights bahh... "
A combo of a phong and a specular give a nice touch and wide range of
control...=)
Christoph Hormann wrote:
> 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] gmxde>
> IsoWood include, radiosity tutorial, TransSkin and other
> things on: http://www.schunter.etc.tu-bs.de/~chris/
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Alan Kong wrote:
> 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.
>
Such "black box" testing is not very effective method for determining
strengths and limitations of this patch. It would be easier to look at
source code or ask me :-)
More seriously, I admit that my documentation for this patch is not very
good, especially this part, which describes limitations and
shortcomings. I try to correct this situation and write some more
comprehensive documentation about this matter, but as documentation
writing is not favourite activity among programmers and English is not
my primary language, this will take some time.
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