Author Topic: IOR and Fresnel  (Read 620 times)

2023-08-07, 15:06:09

aler

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Can you please tell me if it makes sense to use C4D-Fresnel to control the degree of reflection on inclined surfaces? Or does the Physical material, depending on the IOR value, independently determine the correct reflection on the bevels?
The question arose because, for example, with a standard IOR - 1.5, the colors often turn out to be very faded (depending on the degree of glossiness).

2023-08-07, 15:52:59
Reply #1

pokoy

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Physical material already accounts for proper IOR (as does the legacy Corona Mtl).

The apparent fading of colors - I guess that the surface reflects a sky environment, which is probably blue/ish - with an orange/reddish surface this will look like it's less saturated. It probably looks different when used with different color tones for surface and environment. With that said, a very rough surface like the one shown here would not be reflective at all.

2023-08-07, 20:42:39
Reply #2

aler

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Physical material already accounts for proper IOR (as does the legacy Corona Mtl).
Thanks. That's exactly what I was interested in :)
And in the first screenshot I have 2 skies (Back and Impact), and reflects exactly light-blue (Impact).
However, I will experiment...

2023-08-08, 08:23:28
Reply #3

aler

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I don't mind if someone else gives an extended answer about Fresnel :)

2023-09-01, 16:38:04
Reply #4

maru

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There are different models of material appearance which give different results even with the same values. Those models are called Bidirectional Reflectance Distribution Functions (or BSDFs if we are talking about light scattering in general, or BxDF if we are talking about whatever that can be a bidirectional distribution function :) ).
The Corona Physical Material is using Oren-Nayar BRDF (or a slightly modified version of it) while Corona Legacy Material is using GGX. That's why they will produce different results even with the same parameters.
It's the same with the C4D native materials - they are using a different model.
If you wish to keep things physical and working as intended with Corona - it's best to use Corona Physical Mtl.
If you don't like the appearance of Corona Physical Mtl or you find the other material types better suitable for the image you are working on - feel free to use them!
Marcin Miodek | chaos-corona.com
3D Support Team Lead - Corona | contact us

2023-09-02, 14:09:30
Reply #5

aler

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Thanks for the explanation, maru :)
If you wish to keep things physical and working as intended with Corona - it's best to use Corona Physical Mtl.
I do this, I use Physical Material.
If you don't like the appearance of Corona Physical Mtl or you find the other material types better suitable for the image you are working on - feel free to use them!
I'm experimenting...