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Underwater compositing - Color fringe

Posted by Marius Oberholster on Wednesday, December 3, 2014 Under: Quick Blog Tutorial
Hey all!

Today I want to share a little trick with you that GOD taught me on compositing for underwater. Now, granted, this may not be anything new to you, as you may have done something along these lines before using the lens distortion node, but using lens distortion has some draw backs which is why GOD taught me this method.

Problems with using the lens distortion node:
- Firstly, it is a great node and it's very useful for adding that special imperfection to a render, but its dispersion is not a tool that should be used for everything and everywhere and does not add value to every render that's underwater.
- Secondly, the dispersion feature works like the distortion feature - it eats up your corners. You don't see underwater camera footage with eaten up corners anymore and their color is almost as crisp as out of the water, were it not for all the blue.
- Lastly, this effect is not to be added to every possible render you make from a chair in a room to a sunny day outside - it's for underwater or to simulate looking through certain kinds of glass. Please use with discretion.

Now for the practical part! :D
Firstly, you need an image. Most of the time, you can even just grab an old render you did off your harddrive, assuming it already has that misty effect you see underwater. If not, you can render something, add the mist and then move onto this step.

Add one Separate RGBA node and one Combine RGBA node (Convertor Category). In between them, add two blur nodes (Filter Category) and two translate nodes (Distort Category).

Why Separate?
Well, in imaging, you typically have RGB. These three primary colors tend to break-up or disperse as they travel through glass or something similar. Sort of like sifting a solid stream of water - it breaks apart.
In order to get that separation effect, we need to first break our stream up and thus we separate our RGB.

Connect the Red > Translate node > Blur node > Red
Connect the Blue > Translate node > Blur node > Blue
Connect the Green > Green (it's for clarity that it remains untouched and green doesn't typically fringe out).

Make all the Translate nodes relative and only on the X-axes give one a value of -0.001 and the other a value of +0.001 (can be increased like in the setup below). The Y has to remain on 0.
Make the blur nodes relative, correction on the Y-Axis, Fast Gaussian and give it a value of between 0.1 and 0.3 - depends on how blurry you want the fringe to come out - you can use more or less - artist's choice.

Now you simply stick that into your composite node and viewer node and adjust it the way you want it. Just to show you it works, I added a monkey and two cubes to a scene and added the effect. I added a screenshot of the set-up as well, so you can check it out.

(Very quick example scene)

(Node setup)

Have fun making your underwater scenes! Stay tuned as we cover the other elements in future posts. The fringe is just that final step :D.

Thank YOU!!!!!!

In : Quick Blog Tutorial 

Tags: jesus  god  holy spirit  teacher  compositing  underwater  fringe 

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And if any man shall take away from the words of the book of this prophecy, God shall take away his part out of the book of life, and out of the holy city, and from the things which are written in this book.
He which testifieth these things saith, Surely I come quickly. Amen. Even so, come, Lord Jesus.
The grace of our Lord Jesus Christ be with you all. Amen."
Revelation 22:18-21

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Proverbs 30:6

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