CGTalk - Trouble with the Diffusion SSS shader

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chamade

08-06-2004, 07:34 PM

Hello all,

I keep having problems with this shader, where certain areas of the model
(circled in the picture) don't seem get affected by it.
For example, if the attached picture, part of the ear is grey.
I tried increasing diffusion, subdiving the geometry multiple times as
suggested in some threads but can't get rid of those artifacts. :cry:

In this example, the SSS linked light in on the right. The diffusion shader
is in a mib_color_mix slot (same artifact if I connected it directly to a
surface shader), there are 2 additional area lights(raytraced shadows)
and no FG. Actually enabling FG and checking "use irradiance" in the
shader sort of fixes the problem, but I am trying to avoid FG(too slow).

Any help appreciated.

http://www.visenworks.com/SSS.jpg

ASWDesign

08-07-2004, 06:38 AM

I noticed that you are using MentalRay to render this out, Have your tried using Software Render?

ASW

Pixero

08-07-2004, 08:31 AM

ASW design, That wont work since Diffusion is a MentalRay shader. :wise:

Stahlberg

08-08-2004, 12:08 PM

Could that be shadows cast from other geometry? i.e. the eyeballs, the teeth, and for the ear the rest of the skull? In that case, the sss is too strong and deep, not sure what setting exactly would help, maybe lower both the intensity and the diffusion? And insert a simple shadowing geometry inside the skull?
Whether or not that is the actual problem, I think the sss is too strong, visually speaking. :) (Or maybe you just cranked it up to see the problem better.)

chamade

08-08-2004, 04:31 PM

Thanks to everyone who helped and those who tried to :)

I finally got it to work, turns out I've been using the older Diffusion.dll which
obviously had some problems.
In any case, I am not sure I like the Diffusion look more then Subscatter.
Seems to produce a more diffused SSS effect without "hotspots"
(which isn't necessarily bad). Though, I still have a lot of experimentation
to do with it. Anyway, back to tweaking :argh:

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