SSS scale for scattering medium

[mlru]

Two things come into play here, I think:
1. if you have a SSS map you have defined areas where the scattering takes place and where not, so you don't have to take care of these areas.
2. the scattering direction. if you use a forward faceing direction (=> +1) you will see the scattering only from lights, that are behind the object. And then the scattering depth plays a role. objects that are too thick wont let the light rays pass through while thinner ones will.

In my settings, raising the absoption only decreases the scattering effect generally, and I prefer to tweak the scattering value, because having a real scale value (in mm) helps me more than some guessing with the apsoption.

I think, it's fine using absorption in materials like jade, milk or similar where the scattering direction is more disordered (0 or to -1), but for the human body it doesn't seem - right - for me.

[Michael314]

Hi,
sorry for the late reply, but my days off are over, I'm back at work!

I have done some test with a basic setup, using geometry figures.
After a day looking for an explanation why I had so funny results using the Poser Plugin compared to results when setting up the scene directly in Octane, I found the culprit: I had smoothing turned on for the cubes in the Poser Plugin scene. After that, I finally could do some tests.

My test scene is a couple of scaled boxes (with varying thickness) and a square emitter behind them.

Changing the phase resulted in very slight differences only, therefore as a first test, I set scattering to 0.
Please see the second attached picture - all effects you see here are just due to transmission / absorption.

Adding scattering to this will result in darker surfaces on the front! (Which is logical, because light is redirected, unless phase = 1)

Best regards,
Michael

[Michael314]

Hello,
as a first conclusion from this, I agree with Paul concerning absorption, that it should be non-zero.
With absorption at 0, most of the light will be transmitted through the body, with little influence of its thickness, and therefore a scattering map is essential.
Attached is the image I wanted to post last week. It shows the effect around the nose.
However with the recent tests, I suspect that the effect seen here is in fact due to translucency, not scattering.

Best regards,
Michael

[Michael314]

Hello,
OK, I found some settings I'm happy with. I finally used transmission EC maps and also specular maps.
(To be precise, for transmission, I used a mix between red and the EC map, because the EC map alone was too pale.)
I increased the scattering a lot, compared to the absorption (10:1).

The settings are the same for all skin materials, except for the lips I used roughness = 0.1 instead of 0.3.

Best regards,
Michael

[face_off]

Geee, that looks great Michael.

I like your idea of using red + a map for transmission. I will use that! I found you had to have a map in the transmission, otherwise eyebrowse can get too much SSS and try red. Maybe rather than a "mix", use a "multiply".

For her lips - you could probably reduce the roughness even more and increase the bump.

Which figure did you use for that render? Curious to see why here eyewhites are taking looker than her skin to render. Also, eyewhites are another candidate for your SSS shader.

Paul

[Witpapier]

Could anyone pleas mail me a decent preset to load on all textures for sss with all the files needed.... I know this might seem like a easy way agetting around... but it would be a lot of help. [email protected]

[Tugpsx]

Looks like Reby Sky over at Daz.
http://www.daz3d.com/v4-elite-reby-sky

[wimvdb]

Could anyone pleas mail me a decent preset to load on all textures for sss with all the files needed.... I know this might seem like a easy way agetting around... but it would be a lot of help. [email protected]

There are some skin materials in LiveDB. At least one of them (and I think more) have SSS material applied. If I recall correctly it retains the existing materials as well. The correct settings are still a matter of preference.

[Witpapier]

Hi there, I need some help. I have finally figured out a sss material that looks ok... but as you can see from my pictures.. Every time I fidle with sss, its like I lose colour and contrast. My ideal situation would be having the sss with he same level of texture colour... I bet I'm doing something wrong somewhere but i just cant figure it out. Please help.

[face_off]

Hi Witpapier

Your material mix at 0.9 means you are only getting 0.1 of specular - which is OK, but if you are finding you need more shine/reflections, drop the 0.9 down a little (to say 0.7 to 0.8).

For the "paleness" - the skin tone color is controlled by the "texture2" node within "material1" and "material2". To give more color - increase the red component of whatever color is in "texture2". Ideally, "texture2" will be the same for the "material1" and "material2" pins of the "material mix".

I also noticed you are using a "multiply" to combine "texture1" and "texture2" on the "material1" diffuse. Whereas you are using a "mix" node for the same thing on the "material2" node. IMO the multiply is better than the mix, since the mix looses some texturemap detail.

Hope I haven't confused you!

Paul