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13 Nov 2024 05:19:56 EST (-0500)
  Subsurface scattering on a human head (Message 1 to 5 of 5)  
From: stm31415
Subject: Subsurface scattering on a human head
Date: 19 Nov 2004 23:45:00
Message: <web.419ecb4ef78e41e441aa633f0@news.povray.org>
I was reading some post, recent and not-so-recent, on using media to
simulate SSS. I tried it out on some basic shapse, and was fairly
impressed, so I decided to try it on one of the [mediocre] head models I
was working on. Hmm... 5 hours later, I have a skin that looks great at
first glance, but looks worse and worse the more you look at it. The left
is with SSS, the right is without. Both are the same model, the same color,
etc. I have learned this:
1. To use this method with meshes, the resolution must be HIGH. No
smooth_triangles here. You can see that the top of the head of my model has
only a few quads, and with normal rendering it looks fine. but the SSS,
with media inside the mesh, is banded and rough.
2. You really need two models: one for the media, and one for the inside
opaque layer. The *plus* of this is that you can increase the media's depth
in areas of semi-transparent cartilage, like the ears, nose, and eyelids.
This will give an added sense of realism, and even less need for other
complex texturing, in image maps, etc.
3. This takes forever to render with fancy lighting, i.e. radiosity, area
lights, etc. The good news is, it shows up more when in harsh lighting (a
point light more than an area light, for example).

This would not be great for everyday renders, and probably pretty bed for
animations, but for stills where realistism is important, I was very happy
with how my crumby slapped-together test came out.

(You can see where a custom inner form is important. in this image, I just
scaled the head down a percent, and made it opaque. The double shadows on
the nose, and the wierd color of the lips is the result of this. A custom
model for the inside, and a higher resolution outer skin would make this
much better.)

Anyway, I thought it looked a little softer, a little better.

Comments?

-S
5TF!


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From: stm31415
Subject: Re: Subsurface scattering on a human head
Date: 20 Nov 2004 00:55:00
Message: <web.419edb7714cac53741aa633f0@news.povray.org>
Here is antoher image, from an angle less flattering to my model, but better
for seeing the subsurface scattering/media effect. With a smoother skin and
more SSS. This image gains almost a 'heavenly' softness. You can still see,
however, the facets on the back of his head, a place that normally would
need very little detail.

-S
5TF!


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From: Jellby
Subject: Re: Subsurface scattering on a human head
Date: 20 Nov 2004 04:06:28
Message: <419f0913@news.povray.org>
Among other things, stm31415 saw fit to write:

> Here is antoher image, from an angle less flattering to my model, but
> better for seeing the subsurface scattering/media effect. With a smoother
> skin and more SSS. This image gains almost a 'heavenly' softness. You can
> still see, however, the facets on the back of his head, a place that
> normally would need very little detail.

That one looks like velvet! Could you use that texture in a more appropriate 
model (maybe some cloth)?

-- 
light_source{9+9*x,1}camera{orthographic look_at(1-y)/4angle 30location
9/4-z*4}light_source{-9*z,1}union{box{.9-z.1+x clipped_by{plane{2+y-4*x
0}}}box{z-y-.1.1+z}box{-.1.1+x}box{.1z-.1}pigment{rgb<.8.2,1>}}//Jellby


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From: Mike Thorn
Subject: Re: Subsurface scattering on a human head
Date: 20 Nov 2004 07:50:40
Message: <419f3da0@news.povray.org>
Jellby wrote:
> Among other things, stm31415 saw fit to write:
> 
> 
>>Here is antoher image, from an angle less flattering to my model, but
>>better for seeing the subsurface scattering/media effect. With a smoother
>>skin and more SSS. This image gains almost a 'heavenly' softness. You can
>>still see, however, the facets on the back of his head, a place that
>>normally would need very little detail.
> 
> 
> That one looks like velvet! Could you use that texture in a more appropriate 
> model (maybe some cloth)?

I have the perfect model: yesterday I was working on a jewelry display 
like you'd see in a department store displaying necklaces. It was going 
to be a POVCOMP entry but after some feedback from my family I think 
I'll scrap the idea. :) Anyway, I was going to need a "velvet" texture 
for the mannequin. This might work perfectly. Sam, if you want my scene 
to try it out on, I can send you the POV file. I've attached  small 
render of what I have currently.

~Mike


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From: Jim Charter
Subject: Re: Subsurface scattering on a human head
Date: 20 Nov 2004 09:39:12
Message: <419f5710$1@news.povray.org>
Interesting experiment.  One I wanted to try but never quite got around 
to it.

You raise one point I have always thought to be true also.  That you can 
get a better effect with a sufficiently dense NON SMOOTHED mesh than 
with smoothing,... SSS or not.

Of course much of the dissappointment with your test result has to do 
with the plastic consistency of your pigment.  Skin pigment is much more 
variegated than we normally realize.


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