"...only took a few minutes to do..." That would probably rule put anything approaching real time, even on a current SOTA system I suppose. Be neat to have it happen as you zoomed the camera in and out. Probably have to do it in hardware. While we're at it, might as well throw in dynamic crowd generation with variations in gender, age etc. based on parameters you enter. Randomize the clothing too using something like the built in clothing on the old Poser figures. Let's see, 'Computer, give me 50 fit Swedish females, between the ages of 18 and 45. What's that? No, no need to bother with clothes.'

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken