The Screen Actors' Guild, the US union to which most film stars belong, is poised to go on strike in June. But one summer release may be pioneering the way to make future thespian walkouts an irrelevance. Final Fantasy, due to reach European screens in August, uses state-of-the-art virtual actors - sometimes known as "vactors" or "synthespians". The film, a science-fiction thriller set in 2065, has been entirely computer-generated by animation specialist Square. Flesh-and-blood actors contribute basic movement data and voicing.
But anyone hoping to be convinced by the female lead, Aki Ross, is likely to be disappointed. A preview last week in London showed that "she" may look more human than most characters that are software-born, but there's still something wrong. Her skin and eyes look lifeless, and when she runs, her movements are somehow too smooth. Some of these problems also affect Eve Solal, a computer-generated character produced by Parisian animator Attitude Studio. In stills - such as "her" recent cover shoot for women's magazine Madame Figaro - Solal looks disconcertingly real. But in a short video interview, available on her website, she doesn't quite convince. This is because, when computer animators try to simulate human life, they are trying to trick one of our brain's most reliable processes.
"There is a disproportionate amount of mental capacity used for dealing with faces," says Dr Donald Laming, lecturer in experimental psychology at Cambridge University. "If the face isn't quite right, it's not going to work." The brains behind Solal and Ross know they aren't quite there - yet. Mr Jun Aida, producer of Final Fantasy and president of Hawaiian-based studio Square, says: "Our goal was not to create photo-real characters. I don't think technically it's possible with animation. In still photos, we can." He sees his film as creating a new category of high-quality animation, rather than as a challenge to live-action movies. Virtual actors are not even a cheap alternative to the real thing. Mr Aida says the 60,000 hairs on Ross's head took one-fifth of Square's graphic rendering capacity to produce.
"She ended up costing us millions of dollars," he says. "We should have given her shorter hair."
The resulting hairdo, although one of the more realistic things about Ross, does tend to make her look as if she's just stepped out of the salon even when cheating death - but perhaps that's a screen siren's prerogative.
Despite the difficulty in creating faces, realistic body movements are at least as tricky. In Final Fantasy, producers used a technique called motion capture. This involves real people performing the required actions, such as running or walking, while wearing sensors spread around their bodies. Cameras track the sensors, then map them on to the virtual actor. But using this process to create convincing movement is fiendishly difficult, according to Mr Chris Ford, senior product manager for Alias Wavefront's Maya, the software used by many firms to handle three-dimensional models.
With Solal, Attitude has got closer than most to convincing human movement, by basing almost all her actions on those of an actress of a similar build; Final Fantasy's animators, by contrast, have used actors only to model action sequences. It is already possible to fill the screen with computer-generated humans and convince the eye - if you're using thousands of virtual actors, rather than one close up. Mill Film, a few hundred yards south of Computer Film Company, last month won an Oscar for its work on Gladiator, which included a 50,000-strong virtual Roman crowd - an obvious money-saver for the production company. It is partly financial concerns that hold back use of virtual actors as leads. "If money's no object, it's possible now," claims Mr Dave Throssell, head of computer animation at Mill. He adds that computer-generating an actor for a whole film would be expensive, even compared to a star demanding $20 million.
