[Photo provided to China Daily]

Most of the scenes are shot in Harbin, in Northeast China's Heilongjiang province, to ensure that the details－from the advertisements on shabby buildings and the snack vendors underneath a bridge to women's street dances－give the film an authentic local feel.

The cast says that Su is pretty demanding. To create a depressing atmosphere, he told the crew to be as quiet as possible at work and suggested that the cast read Buddhist volumes to calm their minds, recalls actor Zhang Luyi, who plays the mathematics genius.

Wang Kai, the actor who plays the physics professor, says: "I initially felt weird that people on the set always spoke in low voices and chatted little. But after I got used to the atmosphere, I got immersed in my character."

Su also hired university professors to write mathematical formulas for the scenes.

"If there is a math buff in the theater, I do not want him to say that the set looks foolish," he says.

Su, who says that Ang Lee－the first Chinese director to win the landmark best foreign language film award at the Oscars in 2000－is his idol, admits that he wants to emulate him.

"It doesn't mean that I expect to get to his level. But I am trying my best to balance art and commerce."