SAN FRANCISCO — Roland Emmerich had a specific plan when he started casting the lead roles for his feature film "10,000 B.C.," last weekend's king of the box office. There was no way he was going to cast a familiar face.

"I knew I wanted to have good actors who had some talent. But I didn't want someone to say, 'Oh, look, there's Jake Gyllenhaal running after a mammoth.' So we went through the hard job of trying to find unknowns. The problem was that the really, really good actors often get immediately discovered," Emmerich says during an interview at last month's WonderCon Convention.

At first glance, the film's two leads, Steven Strait and Camilla Belle, look like they have gotten lost on their way to a casting call for "Make Me a Supermodel." Strait wears a black leather coat and hat; Belle's short black dress would be fashionable on any runway in Europe. The outfits are a few dozen millennia away from the scant and primitive clothes they wore in the movie.

"I was the only girl," Belle, 21, says. "At the same time, I did not have to do as much training as Steven."

Belle plays Evolet, the woman whom Strait's character, D'Leh, loves. He must save her when she is kidnapped by warlords.

Belle brings more acting credits to the film than her co-star. She has been acting since she was 7, and she appeared in such films as "The Lost World: Jurassic Park" and "The Chumscrubber." Strait, 21, has worked more as a model.

No amount of acting would have prepared them for the ordeals of the shoot. They faced climate changes that went from energy-sapping heat to bone-chilling cold. They were required to use a simplistic form of dialogue to communicate in the film.

And then there were all of the big special-effects sequences in which huge beasts were added long after the actors had completed their work.

That was a big change for Belle, who has done a host of independent films, which rarely have the budget for the amount of special effects that are in a film such as "10,000 B.C."

"In independent films, you spend more time working on character development, the story. In this kind of movie ... people don't care much about your character," Belle says.