How is spectral rendering handled? Is all spectral rendering handled as simulation?  Are there technique more tailored to 'consumer' rendering, such as for real-time or even just 'realistic looking without solving full physical equations'?

I'd like to understand how we handle the rendering of spectral effects.  It seems like a photon needs to be described as a range of wavelengths, and incidence with a surface either 


replaces the original, and resolves multiple new photons across the spectral function, each with their own new vector 
maintains the original (or marginally modified) photon, given a threshold


I would prefer to be pointed in the direction of existing work, but appreciate any coloring of this topic.
The most common way I saw is to have photons of several different wavelengths. One then renders with each wavelength and blends the results into the final image.

"Existing work": Psychopath Renderer and The Secret Life of Photons.