Right way to use fresnel

[christophdoe]

Hey,

is there some information on how to use fresnel the right way with Corona?

Coming from native C4D, we can choose dielectric or conductive fresnel.
So far I understand that we can change the IOR in the reflection settings to control the look, 999 being mirror-like, higher values representing metals and lower values non-metals.

What about fresnel-Maps or fresnel shader. Do I have to put to somewhere to make the materials more realistic?
I looked up the examples on the help pages, they all go without an additional fresnel shader I think.

And a second question. A roughness map goes into Glossiness-Texture I guess. Do you usually put something in the Texture-Input of the Reflection-Channel itself?

Looking forward to get this straight :)

[burnin]

Hi!

 1. About conductive material representation and complex IOR check a topic about Physical Metals. Might help your inquiry.

2. You're correct about the Glossiness / Roughness.
And main Reflection channel Texture is usually used for the Color / Texture i.e. creating appearance of different metals, colors (anodized Al, galvanized...) or thin film effect (aka iridescence caused by oxidation) mixed in a single shader/ material.


Anything specific you have in mind?

[James Vella]

If you have a Roughness texture, invert this for your Glossiness slot.

If your metal Reflect channel is pure white then set your Fresnel to 9999 and you can call it done.

If you do have color in your Reflect Channel then you need an extra step to get the correct reflection at the grazing angle. Or you can use Siger Complex Fresnel plugin if you have a preset metal color in mind.



IOR Map is not required if you set the fresnel value yourself for the material. It can be useful if you have a texture with many different items such as plastic, wood, concrete, metal and want to separate the IOR values using a texture instead.

I just did a post about this recently if you wish to see what I mean about the Reflection color, and use of IOR maps as a reference. I think I should also update it to contain a quick method for simple dialectric's and conductors to include your example.

edit:
Ive just done a short update on this as a short guide:

www.jamesvella.net/blog/2020/4/25/pbr-textures-for-3dsmax-vraycorona-the-short-guide

This is the long version which includes things like mixed materials, ior etc.

https://www.jamesvella.net/blog/2019/9/2/substance-designer-to-vraycorona