I know there are various approaches to PBR, and I’ve read about several of them in the various PBR guides that are scattered about the internet. I’m working on a scene which in which all the materials are dielectrics, which should (according to several PBR guides) mean an F0 value of around 4%. However, UE 4 defaults to a specular value of 50%. The UE wiki recommends leaving this untouched and using roughness to control things, but with an F0 at 50%, that makes every surface awash with reflections, which no amount of roughness (even pure white) can temper at all.
Having read that dielectrics should be between 2 and 4%, I plugged a value of 0.04 into the UE4 spec channel and things looked hugely better. This goes against the recommendation in the UE wiki though.
Am I missing something?