 One year. Seven continents. More than 6,000 naked people--all willing to bare all for  Spencer Tunick  (qv) in the name of art. This globally scaled follow-up to the America Undercover documentary Naked States finds the celebrated and controversial artist at work on his most ambitious project: a one-year trek to all seven continents to shoot people in the nude--individually, in groups and against various man-made and natural backdrops.