I've gotten some decent results with adding basic emission to a scattering medium but it obviously then isn't based on the amount/direction of light in a scene.
Does anyone know if there might there be a way to use the Ray Switch or one of the "info channels" textures like Ray Direction/Surface Tangent/Relative Distance to somehow approximate the "quantum yield" required?
Wikipedia:
The fluorescence quantum yield gives the efficiency of the fluorescence process. It is defined as the ratio of the number of photons emitted to the number of photons absorbed.
The maximum possible fluorescence quantum yield is 1.0 (100%); each photon absorbed results in a photon emitted. Compounds with quantum yields of 0.10 are still considered quite fluorescent. Another way to define the quantum yield of fluorescence is by the rate of excited state decay https://en.wikipedia.org/wiki/Fluorescence