Help with Linear workflow

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Re: Help with Linear workflow

Postby roeland » Wed Jun 05, 2013 10:00 pm

roeland Wed Jun 05, 2013 10:00 pm
kavorka wrote:Hey Rikk.
I am curious what exactly your workflow is.
Also, what advantage does a linear workflow have over a non linear workflow?

thanks!


Have a read: GPU Gems 3, Chapter 24. The Importance of Being Linear.

Rikk The Gaijin wrote:OMG thank you Roeland, I finally understand where the problem was.
So, initially I wasn't using any texture, just RGB colors, but RGB color DOES NOT have a gamma input, that's why the colors were washed out!
Now I have replaced the RGB with a texture containing the same RGB values, and the gamma input is set on 2.2 (by default), so finally I get the exact same image between Vray and Octane!

(img)

Thank you so much, this make me understand a lot more about Linear workflow (which I'm new to it), again thank you so much! :lol:


Are these color values exported from an application? In this case maybe you can make the application export linear values instead of gamma-corrected ones.

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Re: Help with Linear workflow

Postby Rikk The Gaijin » Thu Jun 06, 2013 12:53 am

Rikk The Gaijin Thu Jun 06, 2013 12:53 am
roeland wrote:
kavorka wrote:Hey Rikk.
I am curious what exactly your workflow is.
Also, what advantage does a linear workflow have over a non linear workflow?

thanks!


Have a read: GPU Gems 3, Chapter 24. The Importance of Being Linear.

I was about to post the same link, thx Roeland. ;)
About the RGB values, I manually copied them from Maya (VRay materials don't get properly exported in the obj).
Just in case I will need it in the future, can you explain me a little more in detail how to convert gamma corrected RGB values into linear ones?
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Re: Help with Linear workflow

Postby roeland » Thu Jun 06, 2013 2:15 am

roeland Thu Jun 06, 2013 2:15 am
If you have an RGB value in sRGB space you need to raise it to the power 2.2 [*].

(0, 128, 255) → convert to [0.0, 1.0] range → (0.000, 0.502, 1.000) → gamma correction → (0.000, 0.220, 1.000).

The color picker will do this correction for you if you paste the values into the HEX field at the bottom. Currently it only accepts hex values (which would be 0080FF for the example), the next Octane version will also accept decimal values.


[*] This is an approximation, but it is close. The actual formula is a short linear piece for the dark values and then a curve, you can find the formula on http://en.wikipedia.org/wiki/SRGB

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Re: Help with Linear workflow

Postby Rikk The Gaijin » Mon Jun 10, 2013 3:52 am

Rikk The Gaijin Mon Jun 10, 2013 3:52 am
Thank you! 8-)
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Re: Help with Linear workflow

Postby roeland » Mon Jun 10, 2013 4:57 am

roeland Mon Jun 10, 2013 4:57 am
Tutorial posted here.

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