When his leading lady walks out, a film director (Al Pacino) turns in desperation to computer-generated imagery to replace her; the resulting “synthespian” (Rachel Roberts, with digital trimmings) becomes the biggest star in the world, and the director scrambles to keep the secret. Big news from writer/director Andrew Niccol: Hollywood culture is shallow and celebrity-obsessed! Niccol seems to think that simply stating this earth-shaking theme is enough; he never develops it, and his film remains a puny, pint-sized satire. Niccol’s sluggish pacing belabors his one-joke script, and he makes a major miscalculation: Simone herself is too bland and vapid to justify her superstardom. Exactly Niccol’s point, no doubt, but it means the film has a vacuum at the center that Pacino’s comic spark can’t fill.