Creating Albedo/Specular/Smoothness textures for scratched metal

Rekov

I was hoping to get some general advice for creating scratched metal textures for PBR specular workflow. I know that generally metals will have a dark, nearly black albedo, and a relatively bright specular.

What I'm not entirely sure of is what a scratch would look like across those three textures. I assume that scratches would be brighter on the specular. I've tried making them less smooth, but it's resorted in this weird effect where they pick up color from lights in an odd way. I don't know if they should be represented on the albedo at all.

So far I've been trying to do this by hand in Photoshop, though that's because I don't know how else I'd do it, not because I necessarily want the hand-drawn look.


Rendered in Blender Cycles using the PBR dual mode shader, specular workflow.

EarthQuake

Scratches would be mostly in the gloss/roughness map, and which values you would use will generally be determined by some simple logic.

First, ask yourself what the properties of the base material are?
Then, consider how those properties would change if you scratched into the surface of the material.

Assuming you have a metal that is not polished to a mirror finish, but instead has a bit of wear from age, a scratch in the surface would tend to polish or scrape off the rougher, outer later. This means the gloss/roughness content would be more smooth rather than less smooth where the scratch is.

The albedo and specular would remain much the same, as you're not changing the material type. An exception would be if the outer layer is rusted metal, which isn't metal at all, then the diffuse, gloss and spec would change dramatically for fresh scratch that reveal pure metal underneath.

This basic logic can be used to make common sense determinations regardless of the type of material you're trying to recreate.

Rekov

Thanks for the advice. This has been very helpful.

Would oily colors on the metal behave metallically or not? I.e. should this color go on the albedo or the specular? In any case, I'm starting to worry that my grasp of lighting isn't good enough to really see what I'm doing with the textures properly.

musashidan

Rekov said:

 I'm starting to worry that my grasp of lighting isn't good enough to really see what I'm doing with the textures properly.

One of the tenets of the PBR workflow is that it should hold up under any (reasonable)lighting setup - provided you don't push your values too low/high. So changing your maps to suit your lighting shouldn't be required as it once might have been with the older diffuse/spec workflow.