Maxwell Render | Official public forum

What can the roughness and fresnel passes be used for in post-process and how?

-Brodie

So no one has found a use for these?

NL, did you have any uses in mind when you chose these passes?

-Brodie

Hello Brodie,

Those passes are usual demanded for postproduction purposes, for altering the look of some materials or objects in some way.

The Roughness pass allows you isolate which materials are diffuse and which are specular (by their roughness value). This could be useful when you need to edit in post the reflective objects, or the diffuse ones.
One of the most usual role for this pass is then you rendered your image separating the Diffuse pass and the Reflection pass, for compositing them together afterwards. The intensity of the reflective pass can be adjusted easily, producing more or less diffuse materials, and the Roughness pass is useful for isolate the reflective or diffuse materials to work on.

The Fresnel pass allows you to select the front or glancing angles to increase or reduce the shininess or reflection at those areas (or altering the color at those areas somehow).

Obviously, these adjustment can produce a non physically correct result (the correct way to produce those adjustments is editing the materials themselves and re-launching the render), but sometimes the people at post-production prefer to have the capability of performing those changes at their own risk (like mimicking the DOF blur using the z-buffer).

I hope this answers your question.

Greetings

Dario