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Thread: Maya Curve node and IOR Curves

  1. #21
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    Doh! You're right. It's fixed.
    Attached Files Attached Files

  2. #22
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    Quote Originally Posted by MPaquin View Post
    control IOR curves ala http://refractiveindex.info/ with matching curves.
    True, both the the "curve" nodes and the "remap" nodes (using a ramp) would allow to implement a curve-like workflow in Maya. So the "curve" machinery is there. The main issue I see is, how to drive the input of your curve ?

    For a "spectral" IOR effect you seem to be looking for, a "wavelength" is needed as the driver, rather than a color (although it is imaginable to play with the color "hue" to achieve a similar dependency). Some special shaders that use the "ramp attribute" in Maya actually provide such custom input. So with mia and mila, it is imaginable by extending their functionality as well as the Maya integration to provide such a workflow.

    The only material shader which has kind of a "spectral" IOR effect built into it and can be rendered with mental ray, is the "anisotropic" Maya material when enabling its "chromatic aberration".

    BTW,
    mental ray's early attempt to introduce a "spectral" rendering mode many years back was never exposed because of the existing user interfaces built around traditional "colors".

    The other example you mention, driving the reflectivity based on the "facing ratio" of the surface, is a good example of how "remapping" of certain shader values could work through a curve today. Although the Maya workflow is cumbersome since obviously not designed for that.
    Last edited by steve; September 15th, 2014 at 16:24. Reason: quotes

  3. #23
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    I started messing around with the Gold preset because that is the easiest to recognize and I wanted to make sure what I was doing was accurate and got some interesting results.

    The default Gold N and K values were attained by using a middle value for each rgb wavelenth. For example, red is somewhere between 620-750, so the wavelength used was around 700 to attain the n and k for that component. The result is this:

    gold_old_noGamma.jpg

    Does not really look much like Gold to me, but maybe I'm too used to an 'idealized Gold," and this is truly more accurate? What are your thoughts? Since I wasn't to keen on it, I figured I probably just needed to gamma correct the result, which I did and got this:
    gold_old_Gamma.jpg

    Which looks a lot more like copper or brass than Gold. So I started dinking around with the numbers, and found that if I used the longest wavelength for each rgb color (so for red 620-750 I used 750), and gamma corrected the result, I got a much closer look to actual Gold. The facing rgb value was 235, 175, 49 and an idealized color for gold is somewhere around 245, 179, 33. So not far off at all.

    gold_correct.jpg

    I tried the same thing with copper, but the middle values of each wavelength worked better than using longer wavelengths of each color.

    Default Values:
    copper_default.jpg

    Adjusted Values:
    copper_adjusted.jpg

    Not sure what any of this means and still don't know how to go about getting an accurate n and k, since I don't know to choose the correct wavelength for each rgb component because it seems to vary between materials?

    Does anyone have any idea how to choose the correct wavelength to enter into refractiveIndex to attain the correct n and k values? I feel like I am missing something in my understanding of how this all works.

    In the end it doesn't really matter, as long as the result is the color you are wanting, I'm more curious than anything on what the proper procedure is for this sort of thing.

  4. #24
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    This is why measured data and strict physical rendering for me are a "okay" proposition. (Also why I sound so dismissive about it, haha)

    I just had a job where art direction was wholly inaccurate. And it's usually 96.347% inaccurate. Art directors don't want what *is real.

    They want what *looks real.

    And that's a chunk of perception. It's also why reference for big FX films are guides only and then we embellish. I had to turn off shadows, change what actually reflects. Exaggerate shapes. Add or remove highlights. Swing colors. etc.

    And then when your colors are great someone in the colour suite makes it blue. "Everything was too warm." But it's gold!

    "Don't argue with an idiot, they will drag you down to their level and beat you over the head with experience."

  5. #25
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    Oct 2009
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    A dumb question, but, how do I make the script work? I can't get the window appear.

    *Never mind, figured it out.*
    Last edited by fatjulio; October 8th, 2014 at 04:41.

  6. #26
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    Dec 2014
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    Hello... A great thread guys. I would like to follow it too. Do any of you have the maya shader ball scene file that I could use for testing? I mean the one that you guys have used in your examples on this thread. Or even just the .obj file? I have the .max file of it but I'm using a mac so I don't have a working version of 3DS Max to even export it from Max into Maya. Thank you in advance.

  7. #27
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    Nov 2016
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    Hello, how do make the script work?!!!!!

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