Author Topic: Anisotropic - how to control Refraction Index?  (Read 4285 times)

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Offline adamwade

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Anisotropic - how to control Refraction Index?
« on: December 13, 2016, 06:33:13 pm »
It seams like there should be a way to adjust the refraction index for anisotropic materials?  Is an anisotropic material a fixed refraction index (same as metal)?

Thanks

guest84672

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Re: Anisotropic - how to control Refraction Index?
« Reply #1 on: December 14, 2016, 06:23:00 am »
Correct.

Offline adamwade

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Re: Anisotropic - how to control Refraction Index?
« Reply #2 on: December 14, 2016, 11:40:06 am »
OK, thanks - it makes sense.  However, they need a way to do anisotropic for something other than metal I guess.  Machined plastics for example.  I'm dealing with an actual brushed plastic piece now (that has an extreme anisotropic effect) and the high refraction isn't allowing for the deep dark shadows on the materials.  Easy Photoshop fix, but maybe this should be an added adjustment in the future.

guest84672

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Re: Anisotropic - how to control Refraction Index?
« Reply #3 on: December 14, 2016, 02:39:14 pm »
For machined plastic I would think that you should be able to achieve this by applying a bump map.

Offline adamwade

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Re: Anisotropic - how to control Refraction Index?
« Reply #4 on: December 14, 2016, 05:05:23 pm »
For machined plastic I would think that you should be able to achieve this by applying a bump map.

This part is a polished cone with radial brush marks (extremely fine) and the anisotropic effect is very pronounced.  A bump map alone doesn't give enough effect.  The Keyshot Anisotropic is perfect except the refraction index is too high.  Thanks for the idea though.

Offline bdesign

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Re: Anisotropic - how to control Refraction Index?
« Reply #5 on: December 16, 2016, 12:17:45 pm »
Hey Adam-

Here is a material setup that you might find useful. In order to have the appearance of plastic, a material needs to have fresnel falloff in its reflectance (specularity). Since this is not an available option for the Anisotropic material (as metals are inherently non-fresnel in nature), I created a custom fresnel falloff map with a Color Gradient node (Gradient Type = View Direction), based on the reflectance curve of plastic found at refractiveindex.info, and used it in conjunction with a Color To Number node (with "Output From" and "Output To" values set to the reflectance values of plastic at 0° and 90° respectively) to alter the specular behavior of the Anisotropic material. To start, I set the Roughness X and Y to zero to compare the appearance with the KeyShot Hard Shiny Plastic material, then applied the custom falloff map network to the Specularity channel and compared again. To my eye, it looks quite close to the Hard Shiny Plastic. I then plugged the custom falloff network into Color 1 and Color 2 of a Brushed node, with the "Output From" value of the Color To Number node plugged into Color 1 set at 70% of the original value, then plugged the Brushed node into the Specularity channel. I then dialed in the Roughness X and Y values. I used a duplicate of the Brushed node (without the custom falloff network) in the Bump channel. Attached example renders are a beauty shot in 3 colors, the comparison test before applying Roughness, and some material graph shots along with the reflectance curve chart. I've uploaded the material to the cloud as "Anisotropic Plastic" (Black, Blue, and Purple). Let me know if this helps.

Cheers,
Eric
« Last Edit: December 16, 2016, 01:02:42 pm by bdesign »

Offline Finema

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Re: Anisotropic - how to control Refraction Index?
« Reply #6 on: December 16, 2016, 09:45:34 pm »
Really good job Eric ;)

Offline bdesign

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Re: Anisotropic - how to control Refraction Index?
« Reply #7 on: December 16, 2016, 09:51:35 pm »
Thank you, Philippe :)

Cheers,
Eric

Offline DMerz III

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Re: Anisotropic - how to control Refraction Index?
« Reply #8 on: December 20, 2016, 10:43:50 am »
Bravo, once again.  :)

Offline bdesign

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Re: Anisotropic - how to control Refraction Index?
« Reply #9 on: December 20, 2016, 03:19:09 pm »
Bravo, once again.  :)
Thanks very much, David :)

Cheers,
Eric

Offline LayC42

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Re: Anisotropic - how to control Refraction Index?
« Reply #10 on: December 20, 2016, 10:22:23 pm »
Really impressive Eric. It seems that the material graph for you is, what Lego bricks are for kids (as well all the grown kids).
I should give this a try.
Thank you for this!

Cheers
Marco

Offline bdesign

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Re: Anisotropic - how to control Refraction Index?
« Reply #11 on: December 22, 2016, 07:48:51 pm »
Really impressive Eric. It seems that the material graph for you is, what Lego bricks are for kids (as well all the grown kids).
I should give this a try.
Thank you for this!

Cheers
Marco
Thank you, Marco! Nice analogy...I think I may fall into the "grown kids" category  ;D :o

Cheers,
Eric