Surface roughness images ?
polycounter lvl 8
Where can I find images of a huge list of surface rougheness typically created by Surface Profilometers; I don't care how they look as long as they represent the physically accurate roughness of the surface in an image; obviously they can't look pixelated 
Replies
If you're looking at this for realtime work you're pretty much wasting your time anyway I think.
the representation of microsurfaces in most shaders is pretty primitive ( it's basically just random(ish) scattering, the amount of which is determined by how bright the pixel in your roughness map is.) so even given the information you'll need to look at a shading model that can support it
There are tools that scan roughness accurately. But each renderer uses different value ranges.
So it's in the end up to the artist to develop basic guidelines via experience.
Basically, you take a grungemap (tons of good grunge libraries around) with a pattern that matches your intended surface type (glass is different from brick) and you mix it with feature-specific details (edge wear, accumulation, water damage, etc..) then tweak relative strengths of each map until it looks good in your current lighting context.
That's it. Rinse and repeat.
We have some info here that might help
https://tech.wayfair.com/wayfair-3d-university/knowledgebase/what-is-a-v-ray-material-made-of/
They have a lot of carefully calibrated scan data, matched with accurate shading models.
You could in theory use Render To Texture (3ds Max) or Transfer Attributes (Maya) to extract the roughness.
But then you're converting it to a format that no longer has the correct context.
Besides, it's expensive, and highly specific.