How adding SSS to VrayMaterial?

[BeneZ]

Hello,
I have an VrayMtl and want "only" to add Subsurface Scattering. The material should be paper (a bit more softlooking, translucent).

When I enable Subsurface, nothing happens whatever I do with the sliders there.I spent already some hours in testing...
Then I read somewhere I need to activate refraction, but this destroys my object, makes it only dark.

So my question is, how can I use this Scattering?

And in case I need to use a VrayFastSSS2 (I never worked with that), how do I apply the same settings?
I have attached screenshots of my VrayMaterial.

Many thanks

[joconnell]

For paper try the vray2sided material instead- https://forums.chaosgroup.com/forum/...ndered-version

[dgruwier]

The VrayFastSSS2 is fairly simple to work with, just add it and tweak the settings. It has reflections and diffuse, so you just need to use that instead of the VRayMtl. If you need only the SSS part and want to use VRayMtl for everything else, disable the spec/reflections on the VrayFastSSS2 shader and use a VRayBlendMtl to blend it with the VRayMtl. Beware that you won't get proper energy conservation and that kind of stuff, so you might need to adjust the brightness.

That all being said, like joconnell said, look into VRayMtl2Sided for paper and leaves and anything else that is just flat planes of polygons. SSS requires some thickness to work.

[BeneZ]

Hi, thank you!

My VrayMaterial it is already plugged into a 2sided-material: The same in front and backside. That should be o.k. or has it to be a different material?
(I also have to test, if the Normal Map disturbs on backside, when it points to the back from backside)

The BlendMaterial sounds good! Because I wouldn't need again to tweak everything!
And the SSS2 has a specular-workflow and not glossiness (which makes it complicated to use may maps, as I don't know how to convert them proper).

But: The next problem you mention, is that my Paper hasn't any thickness (It's for some reasons not possible to add any thickness to this object).
I created the material in Substance Painter and there is works fine with a simple SSS simulation.
How can I achieve this without having thickness in Vray?

[dgruwier]

That is specifically what VRayMtl2Sided is supposed to do, create translucency effects on objects with no thickness. Specifically, it lets the back of material bleed through as you shine light on it from behind. And yes, just put the same material in both slots unless you specifically want different materials for either side (like writing on one side only):






The SSS in Substance Painter is going to be a very rough approximation to make it run in real-time, and will let you achieve strange and unrealistic effects if you push it. I'm guessing that it assumes you want to mimic the effect of light bouncing around inside your object, and lets you do it even if there's no actual thickness for the light to bounce around. VRay is less forgiving, and you might not be able match the exact same look. It'll be much more realistic whether you like it or not


As for FastSSS2, the "Specular" options are equivalent to Reflection in the VRayMtl. It has a mappable glossiness slider.

[BeneZ]

Hi dgruwier,

I tested today blending VrayMtl with SSS2. The coat material seems to override everything, not only mapped channels. (Bump, Reflection etc.)
How do you use it, that it keeps all other VrayMtl channels?

Thanks

[dgruwier]

Make it additive. It's not physically accurate, but it might give you the look you're going for.
That being said, I'm not sure why you're still not using 2sided material.. If you can elaborate on exactly what you're trying to do, that would make it easier to help.