Half-hour project, from GPU Gems 3.
It’s not a very realistic effect, since the actual lighting on the cubes comes from the front, whereas the big sun thing is behind them. Also, sometimes rays from further-back cubes actually sometimes appear on top of the frontmost cubes, which spoils the illusion a little. There are ways around this, but they require rendering the same geometry multiple times, which isn’t really possible to do efficiently in QC.
It’s just occurred to me that; of course the lightrays shouldn’t be picking up colour from the the foreground objects. I guess it will be necessary to render more than once, afterall. I’d need a pass where the foreground objects are black, then I render the light rays from the sun, then additively blend in the lit foreground objects on top.
What I’ve got at the moment is essentially just a zoom blur.