A defender of the detachment of the British royal family once said: “We must not let daylight in upon the magic.” Advice which applies to Marc Jacobs, the designer, subject of a documentary airing this month on the Sundance Channel. Jacobs' affection for gay porn stars doesn't diminish his mystique: fashion industry figures are expected to be outrageously homosexual. But take a look at the designer (the most influential of his generation, the narrator declares) in "pigeon disguise" so ambitious and cumbersome that he has to ride in a truck. That epitomizes his whole state of mind, we're told; it also epitomizes the absurdity of the fashion industry. Click for Marc Jacobs thoughtful, chain-smoking; the fashion designer on inspiration; on the horns of a dilemma ("This is so horrible that it is good. Or is it so horrible that it's horrible?"); and, yes, as a pigeon.