What is the best way to convert VRay Reflection Maps to Roughness?

Question

VRay uses a slightly different material workflow that makes use of reflection maps. I know that you can convert a gloss map to roughness by simply inverting it. However I've read that reflection maps can not be directly converted to roughness, but often that's the only map provided (other than albedo/basecolor).

1. Is there any kind of hack or method to convert a VRay reflection map to Roughness?
2. How would you go about converting a VRay material properly to a Cycles material?

Thanks for any advice.

Answer 1

You can adjust the colors with a ColorRamp node.
The result won't be the same, but you can get close.

^{Left: Roughness Map
Right: Reflection map adjusted with ColorRamp}