I’ve been on vacation this week. Kayaked this morning, biked this afternoon (I sound so studly. but it’s all been fairly easy stuff, though sweaty). Catching up on my Wired magazines while waiting for the shower, I ran into this surprising article. Who would have thought the Rendering Equation would be a little article in any popular magazine, ever? Sure, it’s mostly Wired establishing geek-cred – the equation could really use a figure and a bit more explanation to appreciate it – but still fun to see.
They made an error in the units, probably in an effort to eliminate the outgoing direction parameter for simplicity. By using Watts instead of Watts/(m^2 sr), they have to assume that the incident radiance is invariant with respect to direction. In that case you don’t need the integral. In fact, you probably don’t need the equation–that’s only going to work if the whole scene has constant lighting. Maybe that models something like the inside of a Lambertian white sphere?