Some matte objects becomes glossy at glancing angles?

V-Ray V-Ray Common Render Theory
1

I’ve noticed that a lot of surfaces that have a rough, matte finish will become glossy and shiny at glancing angles. For example my smartphone has a matte aluminum finish that appears somewhat diffuse, but if I look at it from an angle, it becomes almost perfectly mirror-like.

Does this phenomenon have a name and is it described somewhere? Does this happen with all materials or only some?

At first I figured that this must be what the “glossy fresnel” feature is supposed to do, but that appears to only affect the brightness of the reflection, not the glossiness.
I’ve been mimicking the effect by adding a fresnel to my glossiness maps just before they go into the vray material.

2

It’s called “Micro Roughness”, and the GGX model has it embedded, it should work on its own.

Here:

microRoughness.jpg
microRoughness.jpg640×480 23.5 KB

3

Isn’t that the definition of our dear old friend Fresnel?

https://en.wikipedia.org/wiki/Fresnel\_equations

4

I believe fresnel deals with intensity, and there’s some mis-wording with wikipedia. :slight_smile:
but i stand to be corrected, ofc.