Quote - Yes there are shortcuts even in unbiased renderers.

A true physics simulation would have the volution of each photo carried out through it's entire path, not just where it intersects a polygon. This would be true volumetric rendering. It is as much out of range right now as unbiased rendering was out of range, computationally, just 15 years ago. Nobody was doing it.

This is most obvious in SSS of any sort.

SSS was the thing I thought of there. How can it be wholly unbiased, I was thinking, if there isn't layers of skin modelled in the mesh, with each layer having some thickness... and then, having a muscle layer modelled underneath that and likely some skeleton under that...

...but I expect I was over thinking it there somewhat!

Yup, render speed is definitely important to me... as important as realism... because I like complexity in an image, often. So my scenes take a long time to render anyway.... it's not that I want a five minute render.

So BB putting all these mathematical heuristics and light physics equations into the biased, but faster Firefly is great, I think.

Like Sam, I can program... I do it for a living... and I'm not terrible at mathematics or algebra, etc, when I need to be. But I'll generally defer to more hardcore mathematicians than myself to come up with the really cool libraries... some open source or MIT licensed... some priced license models... the choice will depend on the reuse / project.

I quite enjoy a spot of gardening myself, when I'm not doing 3d, in the spare time I have.

But I generally plant a lot of stuff already propagated by others... from the garden centre... or grown by more horticulturally astute older relatives... etc.