Shader features

I'm not sure what improvements have been added into the shaders. Just dropping some suggestions here.

Anistropic specular
Parallax
Self-shadowing relief
texture based lighting/dynamic?
Subsurface scattering

[BielBdeLuna]

can't anisotropic specular be faked with normal maps?

I think the specular reflections have to be rethinked by either replace them completely or make them more PBR related. the concept of texture based specular power might go against the energy conservation concept of the PBR, after the icnlusion of a roughness system we have to find a way to do the specular reflection power taking into the angle of view and the normal of the surface, so a Fresnel reflection is taken into account (and this should vary a lot the power of the reflected image, making the texture-based-power meaningless)

I think we could add a Subsurface Scattering token to the material, which forced the material to use a Half-Labertian lightning method on that particular material only.

@BielBdeLuna I'll have to take a look into it. PBR spec/gloss maps are different from the old render system. I get many cases where a well lit room would end up drowning out most textures, making it mostly white. Enabling HDR and exposure increases it even more. The spec maps usually have a black/grey range, with bright regions usually say for example edges of a worn metal surface.

For subsurface scattering we could maybe have a texture map to control regions of the vertex surfaces, like white could be the thick parts where less light can pass through and black the thin parts, like an ear for example, the thick cartelage would have less backscatter than the lobe.