UE4 A PBR question

wirrexx

Hey guys, i've got a couple of questions for those who's more into PBR than i am.

Non metalic vs Metalic

So if i got it correct, The metalness map in UE4, need to either be White or black, nothing inbetween? No greyish?

Secondly, Making something like plastic means 1. Having it black in Metalness 2. More gray in Roughness?


In my albedo, i should only have the color information (what color my materials should be).


I've read in a couple of places that one could give the Roughness a bit of color, is that true?

Tzur_H

Everything you need to know:
http://www.marmoset.co/toolbag/learn/pbr-theory
http://www.marmoset.co/toolbag/learn/pbr-practice
https://www.allegorithmic.com/pbr-guide

wirrexx

Thank you for the Answer, I Guess Microsurface is Roughness and Reflectivity is Mentalness right?

Obscura

Almost... Reflectivity isn't metalness. Reflectivity refers to a colored pbr "spec map", while metalness need only black and/or white. It makes sense to put little transition to between black and white. With the metalness workflow, the color of the reflectivity will be determined from the albedo map.

PBR shaders can be divided into 2 approaches. Specular , or metalness workflow. UE4 use the metalness workflow. With the specular workflow, you would do pretty much the same thing, as you did earlier with the colored spec maps, you just need physically accurate values to make it working good with pbr.

wirrexx

Thank you, that's what i wanted to know, so in UE4 we use the metalness workflow, which basically means my albedo will be a color map with no light or ao information (seperate)
But my metalness will simple be white or black.

That means my Roughness map (which is the other way around where White is non reflective ) will be used for the scratches, Fingerprints, Spots etc etc?

Obscura

wirrexx wrote: »

That means my Roughness map (which is the other way around where White is non reflective ) will be used for the scratches, Fingerprints, Spots etc etc?

Yes. But some of these should be marked in the albedo too. Sometimes in the metalness too. Lets say you have a painted metal, which is not metal (paint is paint, and its not metal) but there is metal under that. You put some scretches on the paint, and that should be marked in the albedo (you want different color for the revealed metal), the metalness (obviously) and in the roughness too because you probably want different roughness for the revealed metal. Fingerprints, dirts and such are usually marked only in the roughness, but depending on the amount and type of the dirt, sometimes it appears in the albedo too.

wirrexx

Thank you Obscura, going try to create a simple sphere to work from and play around with it!

Obscura

No problem. One more thing regarding the topic. When using the metalness workflow, the metalness does a multiplication with the albedo with metals. What this means is that if you want chrome or mirror looking metarial, then you need white or almost white albedo. For gold, you need gold albedo (plus white metalness). And the most of the surface details should come from the roughness, and some of them possibly from the albedo.