news:3fefc08e@news.povray.org...
> Two things.  It seems to me that sub-surface scattering in flesh is a
> slightly different issue than in, say, wax.  The wax is translucent and
> monochromatic.  The particular look of flesh is more involved, what with
> skin pigmentation, skin translucency, and the color(s) of underlaying
> tissues, blood vessels and so on.

Exactly. In fact, media sss works as it should, it's just that actual skin
structures are not those of a Poser model (fortunately). It works on fingers
or ears, but the entire face is a problem. I'm under the impression that
even a good approximation of this would be just too costly, at least for the
type of machines most of us are using.

> Gilles, you did some early experiments with Povman and skin shaders.
> Can you tell us in what way it fell short for you?  I mean to give it
> another try if I can dig up the patch, but I would be interested in what
> your thoughts are on it.

The main problem, actually, was that they were linked to a specific version
of a specific patch and at one point I just wanted to use 3.5... The old
patch dilemma. In any case I think that the skin shaders (and the whole
renderman shader support) are a great idea, but they obviously needed a lot
of additional work to be completely usable. They worked well but only in a
specific set of lighting conditions and I didn't know enough of the theory
and of the shading language to modify them myself. Skin is a extremely
complex and variable material, and a complete skin shader should be able to
reflect (no pun intended) this.
Here are some quick tests with Vicky 3 and her hi-res textures and bump
maps:
Regular POV 3.5, 3-point lighting :
http://www.oyonale.com/histoire/images/vicky3_test.jpg
MLPov, Kitchen probe HDRI lighting
:http://www.oyonale.com/histoire/images/vicky3_hdri_test.jpg

I tend to believe that POV-Ray code could make good skin textures but more
control is needed on the finish. What I think is missing is the possibility
to tweak specularity by having more control on the falloff curve and on the
illumination type. Also sorely missing in regular POV is an angle of
incidence pattern (it's in MLPov) which is extremely useful for more more
things than reflection (where it exists in 3.5). Below is the same Vicky,
this time in Cinema 4D with HDRI and specularity and aoi tweaks. It could be
better but it's getting there (and I'm a newbie so there's ample room for
progress).
http://www.oyonale.com/histoire/images/vicky3_hdri_c4d_test.jpg

Below are details of a series of images I did in POV-Ray 3.5 recently (the
images themselves are not on the site yet), where the characters' skin or
fur were rendered with a faked aoi texture using a slope map linked to the
camera:
http://www.oyonale.com/ldc/images/grandrue_est_bleu_detail1.jpg
http://www.oyonale.com/ldc/images/grandrue_est_detail1.jpg
Note that these images are less "genuine" than the previous tests, since
there was a lot of artifact removal post-render and some compositing.

G.


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