[celoyd]

a clever, possibly elegant, algorithm

It’s just barely clever enough that no one thought of it before. It has to be really simple, because the innermost loop (estimating how cloudy a given pixel is) runs several trillion times.

using tools anyone could use (aside from a massive server farm)

EC2’s m2.4xlarge (> 64 gigs of memory, 8 decent cores) is going for $0.14/hour right now. You could run ten of those all day and spend less than on dinner at a restaurant with cloth napkins.