The light from the sungun can replicate the effect of the sun hitting your cars paint, that's generally where you see the most swirls or spider webbing. Basically its a very strong concentrated light vs the dispersed light of a flashlight (someone chime in if I'm way off lol).
More info here:
http://www.detailingworld.co.uk/foru...d.php?t=202530
There are a bunch of threads about it there.