So... why? If you care about accurate visualization of propogation of light through a complex scene, why not just do a full wave simulation? There are multiple, well studied techniques (Finite Difference Time Domain, Finite Difference Frequency Domain, Finite Element, Method of Moments...). These will give you what the light will 'actually'[1] do, not a guess based off some small sample of training data.[1] Like with all modeling, there are of course assumptions and approximations. Different techniques have different strengths and limits. Still, these are all well vetted, studied and used by people who care about accuracy.
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