Cool, gotcha. It really looks like the same effect can be achieved, and like you say, a whole lot cheaper, with a cloud making the volume, doesn't even require localising but that would further speed things up indeed. I can't actually see any volumetric shadows from your trees at all, though.
I have loads of experiment files with wacky atmo's, great fun to play with. I find you can create an entire atmosphere with more control over colouring and volume by using clouds, you don't need to worry about the relative settings that are altered automatically in an atmo' node, when changing density colours etc. and, usually, because of the extremely thin density of clouds that you need to make a decent haze, the sample count can be kept very much lower than usual. My favourite method is to only enable primary in the atmosphere for the general colouring and rely on clouds to create the volume side of things.
Still, I like what you already have and it is definitely nicely Oriental looking. I think I prefer the lighting in the first iteration the best.
