i'am trying to figure out how materials play together with layers, like diffuse material with a specular layer or a specular material with a diffuse layer. Everything under the subject to better understand SSS and transmission to create a skin shader. Sadly i can't figure it out even after hours of trying and testing. I experience weird hehavior (at least in my opinion, which absolutly has not to be correct
) and don't understand where they inherite from.My initial goal was to have a material which has a 100% diffuse layer and 100% specular layer. Without layers or universal material this wasn't possible if i'am right. Am i? It was just possible to mix a specular material with a diffuse material where i would lose information of the diffuse map and strength of the specular pass.
With the addition of layers i thoughed it would be a piece of cake. Diffuse material with specular layer or specular material with a diffuse layer would provide exatly what i want, right? At least i thought so. Sadly both combinations show weird behavior in combination with sss and transmission and i don't understand why.
Case 1 - Diffuse material with specular layer: transmission bleeds into the reflection pass opposite of the light direction.
Case 2 - Specular material with diffuse layer: transmission bleeds into the diffuse indirect pass opposite of the light direction.
After those tests and reading universal material is quite buggy i hadn't much hope for the universal material. But it behaved quite like i hoped for but still with a few issues and the problem of the materials with layers which i expected to appear in the unversial material as well are nowhere seen.
Case 3 - Universal material with diffuse transmission type: the one most close to my expections. The only thing nagging me is the sss and transmission appear a little less effective than in a diffuse material with same color-map, transmission map and same sss-node. I guess its due to the ior?
Case 4 - Universal material with specular transmission type: With the same sss-node i can't get anywhere close to the effectivness of the sss like in a normal specular material even if i adjust the transmission map and the SSS has more noise than the rest with same amount of samples.
I don't understand the very different behaviors of materials with layers and the univseral material. At least expect them to be somewhere similar when given the same input maps, nodes and values.
I won't go into the visible seems in the universal material, since this seems to be just an issue with the 2020XB1 build.
All tests were made with Octane 2020XB1. All materials have the same sss node (random walk) and without rtx enabled. The material i referring to is just put on face and ear surfaces.
Please correct me if i have wrong assumptions on my interpretation or if i'am missing obivous reasons for the given behaviors. Please enlighten me
Another reason i did those tests where to create really glowing surfaces (like the ears) when put in front of a bright light source. I can't manage to achieve this. I can achieve they glow bright in front of a dark background like her right ear in the renders but her left ear directly infront of the light source always stays more diffuse then i hope for.
I would like to hear what you guys think would be a good setups for a skin shaders, or what do you tend to would be a promising setup. I'am currently messing around with one universal material with random walk sss or a mix-material of a universal material with random walk sss and a universal material with absortion medium (intention behind this approach was to boost the transmission on ears but results into getting hot pixels all over, so i'am trying to figure out the settings to smooth it out).
(I havn't tested 2020XB2 yet and don't know if those might be issues that are fixed)
