SSS2 render element

[R_Cyph]

We are having some issues with the SSS render element from Vray and how
to comp it to give us control over the different elements of the
material. IE. back scatter, front scatter, subsurface.

Is there any way to specifically get access to the back scatter and
front scatter components ? Our head compositor would like to have
control over these elements but as it is, the SSS render element does
not provide this finite control.

Any help would be appreciated.

Thank you.

[Morbid Angel]

I second that, I could not get the same result as the beauty render from the assembly of elements.

[vlado]

For the moment, the V-Ray SSS material does not distinguish between front and back scattering, so there is no way to get them separately. It is on the to do list, so we'll get there.

Best regards,
Vlado

[Morbid Angel]

For the moment, the V-Ray SSS material does not distinguish between front and back scattering, so there is no way to get them separately. It is on the to do list, so we'll get there.

Best regards,
Vlado

Right, but how would you comp the sss2 element, with the rest of the passes like diffuse filter, raw lighting, reflection/specular. I have tried doing the typical where diffuse filter is multiplied over the raw lighting and add the reflection/specular and sss, but that does not give the correct result. What would be the proper math behind the element of sss2?

[Metzger]

(LIGHTING+GI)+(SSS)+(SPEC+REFLECT)+(SELF ILUM) If you want more control then you need to output ((DIFFUSE x RawLight)+(Raw GI x Diffuse)) + (SSS) + ((Spec + (Reflection Filter x Raw Reflection)) + (Self Ilum) . For refraction you don't want to use the refract element. Instead go to your refracted shader and choose Affect Channels under refraction and set it to ALL Channels. That way you can comp the refracted elements. Also all object IDs and material id's will correctly refract which is really cool.

[Morbid Angel]

after doing some tests it looks to me as if the diffuse filter is actually contributing to the sss layer making it brighter. Either that or the raw lighting is contributing too much to the sss. In any case I have a simple sphere on a plane and here is what I got.

[vlado]

The sss2 element should be added to the rest of the scene; using the raw lighting*diffuse filter element will make things brighter, so it might be better to mask the raw lighting in that area (I'm thinking we would have to do that in the shader itself to avoid confusion).

Best regards,
Vlado

[Morbid Angel]

thanks Vlado, that would certainly help.