Hi,
Using the principled BSDF, with PBR metalness workflow, do I need to set Specular to 0? I’m a bit confused if it’s still necessary. my understanding is that diffuse/roughness/bump will give all of the information of how the material acts, for something non metal and simple (such as hard plastics, leathers, suedes).
I get that specularity isn’t roughness/glossiness. Is it a binary choice though?
No, if you don’t have a good reason to change it leave it at 0.5.
0 for example will kill all specular reflections no matter what the material roughness is.
Specular is an artistic value. For dielectrics, use it as such. For many rough materials (i.e. rubber), increasing roughness isn’t enough as the structure of the material looses energy. This would become evident if you modeled the microgeometry and give you a reason to lower the specular when represented on a flat plane. Basically we model rubber as a flat patch of surface, whereas in real life the microgeometry is extremely complex resulting in internal bounces loosing energy. On a flat plane or normal mapped plane, you will always see the environment.
For metals, you can leave it at standard for a fade to white reflections no matter the base color. More accurately you would modulate the color of the metal going into albedo based on viewing angle, and set specular to 0. But it doesn’t really matter, it’s not the color change that will make or break your metal in the end.
You also want to lower, maybe even zero, the specular if faking shadow gaps on simplified geometry. I.e. floor boards with gaps, skirting boards, deep crevice between bricks if you can’t afford displacement and so on.
