Releasing PBR is great news and certainly the right way to go for Sketchfab!
Is there any information about the BRDF model (Ward, Phong, Lafortune, ...) you are using, for the PBR maps?
E.g. What exactly are the "Metalness", "Roughness" or the "Specular" parameters?
The information I am seeking is something like, "We use the Ward BRDF model and our roughness parameter refers to parameter xy in this formula".
Any information would be great for me, because I would like to fit these parameters to some illumination measurements. Accordingly, I need to understand what they exactly mean.
Thx for your help!