A while ago I played around with trying to simulate that effect in digital fusion to try and add some extra little bit of photoness to one of my shots.
I did it by separating the image into each of the channels using channel booleans, merging them back together and then adding transform nodes to each channel. then you can mask the transform nodes with an elliptical mask to simulate the curvature of the lens. I dont know how accurate it is to real chromatic aberration but it looked kind of cool.

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So if I apply it with fresnel, so the effect is stronger when the angle of incidence is greater, do you think that would work?

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I think so, I'm not totally clear on what your doing.. Are you making a lens shader? I can picture this being usefull as a post process effect or as a lens shader that shifted the RGB channels more and more apart as they reached the edges of the virtual lens.

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Just trying to write a physically correct realtime refraction shader, for use on water, glass, soap bubbles, gems etc.

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I think in this case a real time refraction shader that somehow does Dispersion, something like the rainbows you see in a bubble for example, would be awesome but from my limited understanding of the chromatic abberation effect I see it as more of a lens effect that would be applied either in post or as a camera effect like depth of field or lens flare rather than at the material level. Sorry if I'm not getting your meaning man. I really dont have much of a clue beyond using these things for rendering, programming this stuff is completely out of my league.

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Are chromatic aberration and dispersion different things? I thought it was the same principle at work, ie. different wavelengths of light travel at different speeds through the same material, affecting the resultant angle of refraction for that particular wavelength.

Is that your understanding of it?

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--Matt

And its not the programming thats hard, its understanding how the thing actually works, so that I can emulate it.

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--Matt

Yeah, I think chromatic abberation is specifically the result of dispersion in a camera lens. hence the effect is is all about how the refraction is impacting the final images captured by the lens. where as dispersion can be any effect where white light is broken up into the spectrum like in a rainbow. Now that I know what you are trying to make I would say referring to the effect as chromatic dispersion is probably the most descriptive. but really its all the same phenomena right. One way or the other if you could create a realtime dispersion effect in a material and or a realtime camera based effect that looked like chromatic abberation in the lens it would be something unique. As far as I know the only renderers that have this effect are Brazil and maxwell both painfully slow but with great results and there is an after fx plugin that does a fake chromatic abberation effect by shifting the channels around. maybe you could look at some technical info for Brazil's absorbtion/dispersion glass shader to see what kind of maths is involved there.

heres a link to some info about the brazil glass shader.

[Link to wiki.mcneel.com]

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I just want to say that this is becoming a very interesting thread.

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To be honest I was expecting another "Negative IOR" thread.

Which by the way, if I'm writing a refraction shader, I could actually do.

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Please support us and post a [Link to www.digitalartsfront.com] on your website.

--Matt