You could say "Life of Pi" is a dramatic departure from Ang Lee's earlier work, except that everything he does is a surprise.

Lee won international acclaim with social comedies set in contemporary Taiwan ("The Wedding Banquet") and Jane Austen's England ("Sense and Sensibility"). He has made a mystical Chinese martial-arts epic ("Crouching Tiger, Hidden Dragon"), a breakthrough gay romance ("Brokeback Mountain," earning him a best director Oscar) and a Marvel superhero film ("Hulk").

Lee tackles unorthodox material once again in "Pi," the screen version of Yann Martel's bestseller about an Indian boy and a tiger cast adrift in a lifeboat. The film blends touching drama and 3-D spectacle, confirming Lee's reputation as a filmmaker who defies categorization and the conventions of moviemaking itself.

Born in Taiwan in 1954 and college-educated in the United States, Lee is matter-of-fact about the four years of work, demanding computer effects and titanic physical challenges of bringing a beloved fantasy to the screen.

"I had to learn about 3-D, because for live action we don't know too much about 3-D yet. I learned about how to use a digital camera. It does wonders with water and opens up the chances to bring in new illusions," he said.

Making what is essentially a one-character film without a superstar in the role was a major challenge. Lee found his actor, first-timer Suraj Sharma, among 3,000 hopefuls in open casting calls in Mumbai, India. Putting a high school novice at the center of the $100 million production was ideal, he said. Sharma had "no bad acting habits to get rid of." Lee drilled him for three months. "Not only acting. He didn't swim."

The greater challenge was creating Pi's traveling companion, a seamlessly convincing digital Bengal tiger. "Not so much the technology. The supervisors and everybody were good at what they're doing. But learning tiger material to direct that tiger." Lee brought four tigers to the set for the animation team's reference, incorporating the live animals into 23 shots, and basing the film's computer-graphic tiger on King, the most beautiful of the cats.

Lee was determined to keep the tiger wild and unpredictable, not a humanized Disney-style cat. "From Day 1, I made it very clear I don't want anthropomorphism."

With all its challenges, working with digital effects allowed Lee to create the film as he imagined it, he said.

"The starting point is the drama between the boy and the tiger. What's going through his mind, what is his mood facing the ocean and the tiger? Going from there, I generate images. Then when you see the final realization as it's rendered, it's always inspiring. Or alarming. Or frustrating and puzzling. You scratch your head and wonder why the science doesn't add up to what you want to see. I don't care how experienced you are, there's plenty of surprises."

For raging ocean scenes, Lee built the world's largest wave-generating pool in a Taiwan airport hangar.

"In the past, you have a wave move from one side to the other and bounce back. It becomes like a bathtub to me. This way we could get unpredictable wave lengths and interesting textures, like a real ocean."

Adding to the realism, Sharma did all his own stunts, and lost a significant amount of weight to reflect Pi's ordeal. "The rest of us would break for lunch and he would have to go exercise," Lee said. "It's pretty miraculous that he never got sick or injured, had a meltdown or misbehaved."

Lee said he hopes to continue working in 3-D. "If I make not too cheap a movie, I would like to stick with it. We're discovering a new film language, new rules, a new relationship with the audience. It's full of unknowns."

Colin Covert • 612-673-7186