Here is a test I was doing, am very curious though as to why this would take 3:23:18 to render? its all default except for: red decay at 7.0521 in atmosphere main, receive shadows from surfaces is on. /easy cloud 01 default cloud type is the Altcumulus, I set the lightness on the cloud to 1 and edge sharpness to 0.1375 and thats about it. I'm running a 27 inch iMac with a 4 core i7 processor, 16 gig of ram and a 2 gig video card