The original PBR paper cites a materials database made by one of those big Japanese companies many years ago (I think it was Mitsubishi?) EDIT: found it! It’s

The original PBR paper cites a materials database made by one of those big Japanese companies many years ago (I think it was Mitsubishi?) EDIT: found it! It’s called MERL (https://merl.com/brdf https://merl.com/brdf) Modern PBR specifically doesn’t really rely on artists choosing a BRDF though. The idea is to pick one that’s accurate, and expose a handful of variables to control it (roughness and metalness mostly)