Summer starts early in the film business — have the last snows melted yet in the East? — but from now through August, Hollywood has a mission: Convince millions to forego the outdoor pleasures of a summer’s evening and plant themselves in theater seats. ¶ The movie industry’s lure of choice in summer films is spectacle, especially the kind created by visual effects. But the nature of that spectacle is changing. Special effects used to be about the flying saucers, the jumps to lightspeed, the vampires and aliens and monsters. Now, vfx are just as likely to be about the central characters themselves, and can give characterization to roles that never would have been considered the stuff of actors in years past — as this season’s summer tentpoles attest.