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grimoirecg
08-30-2008, 05:06 PM
I've been trying to decipher which of the dozen or so sss options in LW gives the best marble results.
This is the simple skin material.
The fast skin material looks weak in comparison, very plasticy, and the sigma2 material was giving very strange results full of blue artifacts and smoothing problems.
The only problem with this simple skin material is that it's slow to render, since you have to set the samples up high to avoid noise.
This is at 32, dropping it down any lower produces unacceptable graininess.
This took 12 minutes to render on a quad core machine, which is too long for such a simple scene with one area light and FG GI (32 rays)
Doubling the samples doubles the render time.
The same scene with the default LW shader takes 1m 30s.

Also, the way the simple skin shader is set up is not intuitive.
There's a slider called specularity, but it actually controls spec AND reflection.
The glossiness slider below it controls the tightness of the spec but has no effect on the ref.
The Fresnel slider doesn't seem to control the incidence angle of the ref, but the amount of ref, based off of what's already set in the spec slider.
It would also be nice to have an amount slider below the the ref blur check box. There are only controls if you used interpolated ref.
These controls could certainly have been set up in a more intuitive way.

grimoirecg
08-30-2008, 05:27 PM
Another variation.

grimoirecg
08-30-2008, 06:31 PM
At 16 samples some parts remain quite noisy even after noise reduction in PS.

lardbros
08-30-2008, 07:35 PM
Also, the way the simple skin shader is set up is not intuitive.
There's a slider called specularity, but it actually controls spec AND reflection.
The glossiness slider below it controls the tightness of the spec but has no effect on the ref.


This is exactly how the mental ray in 3dsmax shaders are set up, so it seems to be an industry standard thing for the moment. Also Vray has the same setup with its shaders.

The spec controls the amount of reflection (which, technically it actually is) and the glossiness (if, reflection blur is turned ON) controls the glossiness of the spec (which is infact reflection). It makes sense to me.

But those render times seem a bit high... what kind of PC do you have?

grimoirecg
08-31-2008, 07:39 AM
No, the mental ray sss shaders (at least the fast skin) have separate controls for spec and reflection and their relative shininess - in fact you have a primary and secondary spec as well as reflection, all controlled separately.
This is a much superior solution with a lot more control (see image)
For example, one thing you can't do with this LW shader is turn spec off and only have reflection, or even have low specularity and high reflection amounts, they're tied together.

lardbros
08-31-2008, 07:45 AM
No, the mental ray sss shaders (at least the fast skin) have separate controls for spec and reflection and their relative shininess - in fact you have a primary and secondary spec as well as reflection, all controlled separately.
This is a much superior solution with a lot more control (see image)
For example, one thing you can't do with this LW shader is turn spec off and only have reflection, or even have low specularity and high reflection amounts, they're tied together.

Im not really sure what you're after? You want a fake specular, white spot type, highlight PLUS a reflection?? (which in real life is the specular)

grimoirecg
08-31-2008, 08:28 AM
That's how this shader currently does it, and if it is going to do it this way, then it would be better to have separate controls over the reflection and specular, as is the case with mental ray sss.

RebelHill
08-31-2008, 08:38 AM
personally simple skin wouldnt be my immediate choice for doing marble with... id go with either SSS, SSS2, or quite probably Sigma2.... perhaps have a go using this preset...

www.presetcentral.com/preset/124/

as a starting point for you... just change the colours out for shades of white/grey/cream

grimoirecg
08-31-2008, 10:34 AM
I'm having problems with the sigma2 material.
Even when I drop my model into the standard preset scene, with your material, just changing the colour, I get this result, with all the strange discolourations which look like smoothing issues. I got the same when trying it myself yesterday.
It's strange because none of the other sss materials I tried have any problems with this model, and other models with the sigma2 result in similar artifacts.