“Monsters vs. Aliens” opens with an old 3-D gag: A ball bounces directly into the audience, causing moviegoers to instinctively scoot back in their seats. But the resemblance to old-fashioned 3-D ends there. The film, in theaters Friday, relies on entirely new technology — much of it developed during production — to lend depth to an epic battle in outer space and drama to the collapse of the Golden Gate bridge as four modern monsters fight to save Earth from alien invasion.
