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david van brink // Wed 2010.04.21 07:41 // {after effects pixel bender}

AE: Omino Glass, A Pixel Bender Filter

download: ==> omino glass 32 <== a pixel bender filter

There was a flurry of interest in "chromatic aberration" a while back, like here. I’d actually played with it a bit, simulating lens-effects, but only now have gotten around to weighing in on it.

The implementations I’ve seen work by splitting out your RGB and moving them around a little bit independently.

Here’s my weigh-in: Come on, people! The spectrum has more than three colors!

I find that five to seven is about right. I’ve implemented this combined with refraction into a pixel bender plugin.

omino_glass_title_card.jpg

Refraction happens when a ray of light changes its direction as it passes from one substance to another, if they have aaah, varying, that is, if they have different, um, refractive indexes. And that’s how aaah magnifying glasses work. See.

It looks like this.

The blue lines are rays of light moving up, or cast-sight-rays going down. It’s all very technical.

But I’ve got this Pixel Bender filter, right?

The filter takes in two images: a bump map (the refracting surface) and an image to view through the refraction. Here’s a bump map:

ripples.jpg

And here’s a source image:

Those chairs are known as “Chadwick Modular Seating”, from Herman Miller, designed by Don Chadwick, who later designed the Aeron chair, and that room hasn’t been that empty for, like, six years, after my girlfriend moved in and filled it up with shoes and stuff. So anyway.

And here’s the image, through the omino_glass Pixel Bender filter:

Now the fun part. Chromatic aberration happens when different colors are refracted by different amounts. Here’s the same image with just a touch of chromatic aberration applied:

Livens it up a little bit, yes?

The “flat” parts of the image, under the non-sloping parts of the bump map, appear undistored, and uncolored. But the distorted parts of the image have their colors splayed out a bit.

That’s chromatic aberration, comma, simulated.

By the way, you can get this effect in After Effects using CC Glass and overlaying multiple tinted copies, with slightly different settings for Height, and adding them back together. But that’s a lot of layers and settings to juggle; my pixel bender filter does it all in one at 32bpc instead of 8.

Here’s a test grid set with no basic refraction, and lots of chromatic aberration. This leaves the central green portion of the spectrum centered on the original image.test_grid.jpg

The inset image is the bump map.

We can see how omino_glass breaks the spectrum up into seven regions. It’s arbitrary, but I like the look.

And here’s a little demo showing the filter in motion, animated in After Effects, out on the ‘Tube.



click for
content

download: ==> omino glass 32 <== a pixel bender filter

Other chromatic aberrations of interest, from some of my favorite blogs:
ae-tuts
maltaannon
satya meka

4 comments
rs // Tue 2010.05.4 01:231:23 am

Superb, thank you!

Harry Frank // Thu 2010.06.3 17:055:05 pm

Love it! I mention it in my next episode of RGTV and in a new preset I am posting for Red Giant People.

Thonbo // Fri 2010.07.2 01:251:25 am

ill try this out in flash at some point, this is great – ive been a great fan of the displacementmap filter and this add a serious take to that category

ill even try to add some lines of code to make you able to designate the starting point of the filtermap (mappoint) this is very usefull for lens effects

david van brink // Fri 2010.07.2 08:288:28 am

^ I’d love to see where you take it!

I havent tried it in Flash. (It might be necessary to restructure somewhat, I think there’s some limitations to do with function definitions in Flash vs AE Pixel Bender.)

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