The relationship between Reflection Amount, Glossiness, and Diffuse.

[joconnell]

That's the thing. Metal never ever gets "diffuse", it's just the more that it's reflection gets rough / soft / glossy, the more it starts to resemble just normal flat lambert. Since a metal has no diffuse, only a reflection colour, I just made the reflection colour the same red as the diffuse material above it.

[RockinAkin]

Yes I understand that metal has no diffuse component - the example I posted above with roughness going from 0 to 100 is NOT a metal material.
It's attempting to replicate a dielectric material... where the rougher it gets, the more diffuse it gets, and the smoother it gets, the more reflective it becomes. Does this make sense?

[vlado]

It's attempting to replicate a dielectric material... where the rougher it gets, the more diffuse it gets, and the smoother it gets, the more reflective it becomes. Does this make sense?

No, not to me, but have you tried playing with the GGX BRDF in the 3.0 nightly builds?

Best regards,
Vlado

[Rens]

I was doing a bit more research into this and discovered that Maxwell Render's BSDF behaves very similarly to what Rens and I were talking about.
The material is a pure red color, and only the BSDF's 'roughness' parameter is changed in these images:

This material confuses me, it looks like it blends from a dielectric with Diffuse set to black and a slightly tinted Reflection, to a material with Diffuse set to red with a rough Reflection.

Also, for comparing the two spheres an HDRI with some nice highlights works better, they're different though. : )

And I'd like to see a test with GGX as well!

[RockinAkin]

Edit: I've updated the graphic above to have correct results now.

Vlado - I gave GGX a brief test run last week and liked the results so far! I'll keep you posted as I get a chance to test it further, perhaps in a character soon.

[zoranm]

I'm a little bit confused now. I always thought that Fresnel IOR is applicable only to dielectrics (non-conductive materials) and metal behave in a different way (IOR nor applicable). Does that mean that no one, so far, discovered a formula for calculating how light behaves when interfacing with conductive metals?zoran

[Rens]

The Fresnel equation using only IOR (n) is what most renderers have implemented. The Fesnel equation using IOR and extinction coefficient (k) is what you can use for metals as well. However, as it takes longer to calculate and because you can get close by other means as well is I'm guessing the reason why the simpler formula was implemented.