Brian Sharpe

I think the sqrtPiOver8 factor might be an internal BSDF implementation detail, rather than something that should be done externally. For example, MDL already applies this factor internally. https://github.com/NVIDIA/MDL-SDK/blob/master/src/mdl/jit/libbsdf/libbsdf_hair.h#L174

> MDL applies the π/8 factor for both longitudinal and azimuthal roughness I don't think it does. The MDL hair_prepare_roughness() function in that github link I posted only applies it...

I think might need some more changes. In its current form, someone can't tweak the TT and TRT scaling factors. So I'm thinking of two potential changes to accommodate this....