Thanks for the assets! Indeed, the amount of sample does not change much, it looks like the artefact are more visible around the sphere poles. We are working on pre-filtering the env map but we'll take a look at this anyway (can't exclude their is a bug somewhere). FYI the metallic and specular shader are 99% the same,…
Uhm. The way I understand oxidized metals (and I could be very wrong here) is that for a metallic texture it would simply have lots of areas with 0.8~1.0 and lots of areas with 0.0~0.2 for where the rust would actually be. I had some guy at work that insisted that the texture would be medium grey and I told them I thought…
you're right, in 99% of cases it should be black or white. however there are exceptions and rust is one of them. minor science bit here: you may remember from school that chemical reactions are irreversible, and usually happen "instantly". the same is true of oxidation, once a molecule becomes oxidized it stays that way…