Chromatic Dispersion Fake

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  11 November 2013
Chromatic Dispersion Fake

Few days ago I was overwhelmed by this thought that there are quite few things which are simply impossible to accomplish using native renderer. I decided to recreate simple concept of chromatic dispersion using existing functionality. Unfortunately my first thought was dead end. Idea was to combine 3 transparent materials (each with single wavelength absorption ) with slightly offset IOR for of red and blue materials. Unfortunately it's not possible to mix materials in this way and the only way around is to render each separately and combine it in post. My second thought was to use mighty Fresnel shader. It's not by any means physically accurate but it may work in some cases. The trick is to make separate materials for front-facing and back-facing normals. Front side should be normal transparent material (with 100% white absorption, otherwise it doesn't work), backside should have Fresnel shader in transparency channel with three pure RGB knots surrounded by two white ones. Those knots should be on the far right side of gradient very close to each other.

R15 was heavy on GI side, R16 should be material oriented in terms of rendering improvements (volumetrics, chromatic dispersion, coating like car paint, BSDF and other *DF's stuff)

Here is file with example

Direct link is above yellow stars.
Attached Images
File Type: jpg Chromatic Dispersion_0001.jpg (44.1 KB, 195 views)
  11 November 2013
Nice one.
But if you want to get several options of dielectrics:
1. you can invest in remotion spectralMagic, which has 5 specular layers, dispersion, thin film... for ar-material... about how it works with physical, i don't know... nobody from maxon show options for xmbsampler
2. pyAPI sample library has frensel source shader, you can (easy) to develop poorDispersion like in renderman

Last edited by ilay : 11 November 2013 at 09:56 AM.
  11 November 2013
Not sure how accurate it would be in regard to refraction/reflection but there are plugins to create chrom. aberration in post, for example Red Giant Looks
  11 November 2013
Very nice approach !
I recently came across with a similar result by using Fresnel in the Transparency channel.
It is a nice way faking dispersion on glass.
However, there's a nice plugin for Cinema, that does that really good and fast:

Spectral Magic



  11 November 2013
Thanks for response everyone.
Spectral magic seems nice and it looks like it's physically plausible.

This time I will refrain from comment on Maxon's lack of fundamental functionality.
  11 November 2013
Originally Posted by AdsovonMelk: This time I will refrain from comment on Maxon's lack of fundamental functionality.

Not really.
  11 November 2013
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