4.0 Principled IOR/Specular Doesn't Work with Metallic
I don't know if this is so much a feature or just an error in 4.0, but the whit-ish Fresnel reflections on a metal material should be adjustable with the IOR floats on Principled shader. I could be wrong, but this is the way it worked prior to 4.0. Here are screenshots of a metal material with Specular set to 0.5 and 0.0 respectively both in Blender 3.6.5. As you can see, the Fresnel refraction toward the edges reverts to a solid colored reflection when Specular is 0.0.
However, in Blender 4.0, when Metallic is on, the Fresnel effect on the metal material reflection remains unchanged no matter what either IOR or the Specular IOR Level multiplier are set to.
3 Comments
I'm a noob in shaders but isn't metallic supposed to be overriding specular?
nope- specular and metallic are different workflows, sure, but when you're talking about shaders, "specular" determines how strong a reflection is. It breaks energy conservation (and along with fresnel is why toy story doesn't look realistic) and is useful for cartoony shaders and adjusting NPR shaders.
Indeed, my bad... Had to re-read the documentation about it:
Principled BSDF — Blender Manual
Anyway, this should be reported via menu Help > Report A Bug.