Author Topic: PBR values for alloys  (Read 9732 times)


I'm getting a little confused with following PBR standards for metals.
Generally I use a black metallic map for dielectrics and white for metals, including alloys and other metallic materials. I would only use greyscale values for rusted/oxidized metals.
If I make a make a bronze material and I give it a dark reflection color, the PBR validate filter marks it as incorrect, because the color should be much lighter, or I need to lower the metallic value changing it to light grey. Does that mean that only for pure metals a completely white metallic map should be used? and for alloys and similar materials it should be a greyscale metallic map?


Alloys are are by definition 100% metallic but, as you mention, oxides are not.
Pure bronze is really quite light in color, similar to brass but a bit more red-ish.

But bronze objects are very often covered in a (thick) layer of oxide.
On things like statues this is usually an intentional patina, where acid is used to speed up the oxidation and the result is often dark brown or black and polished to a shine.

If the patina/ oxide is thick enough this is 0% metallic. Sometimes you still see some metallic sheen through the layer of oxide though. A gray metallic value makes sense here, but the common metallic workflow is, technically speaking, not designed to use gray metallic values.
For this reason it's often advised to make materials either purely metallic or purely dielectric. But this makes it impossible to make these 'transition' materials without writing separate shaders. So studios often have their own rules on whether or not to use gray metallic values.

Thank you, that makes sense!