[alkonaut]

A naive spectral path tracer can be less complex (code wise) than a "normal" one. You just trace each photon with its wavelength instead of tracing RGB (or some other full spectrum) per path. Since this abstraction is closer to physics, it makes a lot of code easier to reason about. Wavelength dependent refraction is straightforward, you just use the index of refraction for the photon you are tracing.

I find this code base extremely easy to read despite not being a C++ (It has that Carmackian quality). Pretty easy to use to port to the language of your choice. https://github.com/TomCrypto/Lambda To get the kind of effect you see in the youtube video you'd render diamond or something with extreme refraction.

This is far from real time though of course. It will run an order of magnitude slower than anything you can do with full spectrum rays. So doing it in realtime would probably be just like subsurface scattering is done in real time: you just have to cheat. Perhaps there can be some inspiration from the real thing though.