Hmm I enjoyed reading this
Been a while since I worked on the PBR system, refreshing my memory on it was a fun exercise!
@Norbyte
You'd still need data to cover AO. Specifically AO on a microscopic scale such as cracks in stone or tree bark.
@Rada Torment,
Good links and decomposition of the textures. If anyone wants more in-depth knowledge on PBR systems I would also suggest looking at
Frostbite's notes and several short Unreal papers on PBR lighting. Not for the faint of heart, though
You're right that macro-occlusions are handled by the SSAO techniques.
Specular micro-occlusions can be handled by a slight modification on the Fresnel coefficient in a PBR system. This leaves diffuse micro-occlusions. You're right that this is currently not used. We opted to put other data in our free GBuffer spots for gameplay related features. Also not a fan of putting diffuse micro AO in the texture itself, but for now that's how artists work if they truly want some specific AO adjustments, but generally it's not needed.
The free channel in Tinkerer's post is just labeled AO because it's empty and supposed to be used for that. Not now, then maybe later. Our engine keeps evolving from game to game, so looking to the future is often not a bad idea during development
