IOR PBR suggestion

[ghost]

Hello. I suggest two parameters for glTF. Extension: KHR_materials_pbrDensityIor (formely PSM_materials_pbrDensityIor i.e. prismarine render library).

• densityIorTexture and densityIorFactor (vec3) - IOR of surface, can be used with plastic, non-metallic surfaces, density is something alike subsurface scattering (insider diffuse), it means how much clear surface Insider, third parameter I have no idea
• baseColorFactor and baseColorTexture (RGB i.e. vec3) - filtering of transparency, not refracted/promised light will reflected or absorbed.

In general, can be combined with pbrMetallicRoughness or specular glossy system. I suggest it, because most engines uses IOR and transparency parameters.

[emackey]

We're gathering suggestions for next-gen glTF material settings in #1442. Merging this issue there, please chime in there with additional comments or suggestions.