Fresnel Conductor Nodes

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Martin
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Fresnel Conductor Nodes

Post by Martin » Fri Nov 10, 2017 12:14 pm

Hi guys,

another gem by nudelZ (BA)!

2 different shader nodes for fresnel reflectance of conductive materials.
One has a typical interface for creating conductive materials, input your n, k values manually.
Other for more artistic use, has interface for setting Reflective and EdgeTint colors: http://jcgt.org/published/0003/04/03/
Light reflecting off metallic surfaces is described by the Fresnel equations [Born and Wolf 1999], which are controlled by the complex index of refraction η = n + ik.

Together, n and k determine the two characteristics of the Fresnel curve for a material: the reflectivity at normal incidence and how quickly it fades to white at grazing angles. However, this parameterization presents some artistic challenges because both characteristics depend on both parameters. An artist would ideally manipulate each property independently and have them on a unit scale. This paper describes a remapping for the approximated unpolarized Fresnel equations of n and k to the more intuitive reflectivity, r, and edgetint, g, both in the range from 0 to 1.
Useful link: https://refractiveindex.info - use n, k values for R, G, B wavelengths.

Edit:
added Conductor Shader by pixelgrip!

Cheers
Attachments
Metal BSDF.cyg
(106.43 KiB) Downloaded 61 times
Metal BSDF (Artistic).cyg
(179.58 KiB) Downloaded 56 times
MetalConductor.c4d
(414.24 KiB) Downloaded 76 times
nk_metals.png
nk_metals.png (924.21 KiB) Viewed 1943 times
Last edited by Martin on Thu Nov 16, 2017 12:37 am, edited 6 times in total.

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Martin
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Re: Fresnel Conductor Nodes

Post by Martin » Sat Nov 11, 2017 10:14 pm

Post deleted. Inaccurate and too complicated setup.
Last edited by Martin on Thu Dec 28, 2017 12:32 am, edited 4 times in total.

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Martin
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Re: Fresnel Conductor Nodes

Post by Martin » Sat Nov 11, 2017 10:15 pm

Post deleted. Inaccurate and too complicated setup.
Last edited by Martin on Thu Dec 28, 2017 12:32 am, edited 3 times in total.

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Martin
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Re: Fresnel Conductor Nodes

Post by Martin » Sun Nov 12, 2017 1:31 pm

Update - added groups (first post).
https://refractiveindex.info - use n, k values for R, G, B wavelengths.
Attachments
3.png
3.png (19.92 KiB) Viewed 1854 times
example.png
example.png (38.29 KiB) Viewed 1893 times

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Brandroid
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Re: Fresnel Conductor Nodes

Post by Brandroid » Tue Nov 14, 2017 4:39 pm

Well, I can't say I fully understand it, but those are some great looking results. Thanks for sharing Martin!

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Martin
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Re: Fresnel Conductor Nodes

Post by Martin » Tue Nov 14, 2017 5:37 pm

Brandroid wrote:
Tue Nov 14, 2017 4:39 pm
Well, I can't say I fully understand it, but those are some great looking results. Thanks for sharing Martin!
OK, skip the post 2 and 3, I should delete this, but wanted to show the different manual way (inaccurate) to do the same.

It's easy just:
1. Use Metal BSDF node.
2. Use this link https://refractiveindex.info
3. Choose material there
4. Input wavelength value 0.65 for Red (that's 650 nm).
5. Copy n value to the node nRed field.
6. Copy k value to the node kRed field.
Do the same for green and red wavelengths:
0.53 for Green (530 nm).
0.47 for Blue (470 nm).
Copy n and k values to the node, that's it.

Wavelength to Colour Relationship - https://academo.org/demos/wavelength-to ... ationship/
Attachments
nm.PNG
nm.PNG (6.83 KiB) Viewed 1847 times

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Brandroid
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Re: Fresnel Conductor Nodes

Post by Brandroid » Tue Nov 14, 2017 9:23 pm

Okay. Now I get it. Thanks for the explanation. Got some great results with your pre-made n/k groups. I also made a brass now that it makes sense. ;)
fresnel conductors.jpg
fresnel conductors.jpg (496.32 KiB) Viewed 1839 times
brass-crab.png
brass-crab.png (557.64 KiB) Viewed 1839 times

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Martin
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Re: Fresnel Conductor Nodes

Post by Martin » Tue Nov 14, 2017 9:40 pm

Nice!
If you notice, you can slightly change wavelength values, that will give you different results.
And there are different sources as well, no idea which to select :D
Experiment.
Attachments
Sources.png
Sources.png (21.54 KiB) Viewed 1837 times

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Samurai JKM
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Re: Fresnel Conductor Nodes

Post by Samurai JKM » Wed Nov 15, 2017 4:44 pm

This is very cool and precise stuff Martin! Thanks

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Martin
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Re: Fresnel Conductor Nodes

Post by Martin » Wed Nov 15, 2017 8:38 pm

Brandroid wrote:
Tue Nov 14, 2017 9:23 pm
Okay. Now I get it. Thanks for the explanation. Got some great results with your pre-made n/k groups. I also made a brass now that it makes sense. ;)
Samurai JKM wrote:
Wed Nov 15, 2017 4:44 pm
This is very cool and precise stuff, Martin! Thanks

Guys,
I deleted 2nd and 3rd posts, because of complicated and inaccurate setups.

Added fresh Conductor Shader v2 (based on http://jcgt.org/published/0003/04/03/) by pixelgrip, the man who created Thin Film Shader, which I reproduced in Cycles 4D before.

I like this setup better because you can easily combine with Thin Film Shader (like heat oxidized metal).

C4D file has 14 metals (copper, nickel, silver, chromium, brass, titanium, platinum, lead, tungsten, zinc, mercury, iron, aluminum and gold).

Added to the top post too.
Try this one!

An example below - Thin Film Shader combined with Conductor Shader.
Attachments
Conductor Shader v2.c4d
(1.08 MiB) Downloaded 53 times
Conductor Shader v2.cyg
(451.8 KiB) Downloaded 52 times
Heat.jpg
Heat.jpg (227.88 KiB) Viewed 1792 times

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Brandroid
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Re: Fresnel Conductor Nodes

Post by Brandroid » Fri Nov 17, 2017 3:50 pm

Martin, that heat oxidation looks awesome. Can you show us how you used the thin film to achieve that?

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Martin
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Re: Fresnel Conductor Nodes

Post by Martin » Fri Nov 17, 2017 4:11 pm

Brandroid wrote:
Fri Nov 17, 2017 3:50 pm
Martin, that heat oxidation looks awesome. Can you show us how you used the thin film to achieve that?
Thanks, sure.
Attachments
Heat Oxidized Metal Setup.c4d
(1.13 MiB) Downloaded 59 times

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Brandroid
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Re: Fresnel Conductor Nodes

Post by Brandroid » Mon Nov 20, 2017 3:37 pm

Thanks for sharing Martin. This setup is great for surface smudges and stains on metals too!
tarnished chrome.jpg
tarnished chrome.jpg (122.32 KiB) Viewed 1704 times
stained chrome.jpg
stained chrome.jpg (187.56 KiB) Viewed 1704 times


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