Movie fans know that their action hero Superman does not really fly.And, in the movie Superman Returns, another visual trick is played on viewers.The man they see flying is not real.He is what is called a virtual actor.The first step in creating this digital actor is to have a real person stand in a room called a light stage.A computer then captures the outlines and shapes of his face and records how they throw off light .Paul Debevec is with the Institute for Creative Technologies at the University of Southern California. "We can light them with very specially computer-controlled illumination and take photos of them from seven different viewpoints with high quality digital still cameras." Mr.Debevec is part of a team working to create computerized images of people, objects and environments that look and act real.The light stage permits actors to be turned into digital versions of themselves much like the blue creatures in the movie Avatar.The real world could soon be using a similar technology.Computer experts at the Institute are developing a 3-D video teleconferencing system.It would send a video image of a person into a meeting room.That image would be able to work with the people in the room, who would see it in 3-D without special eyeglasses.Paul Debevec says: "The person who is being transmitted to a remote location can actually look around at the people in the room and everybody in that room knows who they're looking at .And that's such a fundamental part  of human communication." He believes the business world will begin to use3-D video teleconferencing in the next five years." It's also a medium with which young people today are particularly comfortable," he said.A demonstration of an interaction between an earthquake survivor and students may be possible in a year.In 10 years, we may be able to play 3-D video games without special glasses. Why does the author mention the movies Superman Returns and Avatar in the passage?
To compare their different styles. To explain 3-D film-making technology. To attract more readers to watch3-Dfilm. To describe the origin of 3-D film industry.