Director-producer-writer Michael Mann says he began developing the idea for this film a few years ago, after reading about Stuxnet, a computer worm that attacks industrial programs - including those that control factory assembly lines, amusement park rides and nuclear centrifuges. "As a piece of malware, it was the first digital weapon," the filmmaker says. "It was a stealth drone. It would hit, and it would have an effect that the target didn't know about for 18 months. If it was discovered, it destroyed whatever discovered it."

In the story - which Mann conceived and co-scripted with first-time screenwriter Morgan Davis Foehl - a nuclear power plant in Hong Kong is attacked by malware, causing a near meltdown.

Wang plays Chen Dawai, a captain in the cyber defence unit of the People's Liberation Army who's entrusted with tracking down the elusive hackers behind the attack.

Chen seeks to enlist the help of Nicholas Hathaway (Chris Hemsworth), a notoriously skilled "blackhat" hacker (the term "blackhat" refers to someone who violates internet security for illegal gain). The problem is that Hathaway - who studied at Massachusetts Institute of Technology with Chen - is serving time at a federal penitentiary. After Chen helps negotiate Hathaway's release, the two men lead a team across countries and continents to track down the perpetrators before more targets are hit.

Mann exhibits his usual deft touch with the visuals - many scenes are shot with an unnerving intimacy - and his film's characters have complicated back stories. Even if the audiences never hear them, he ensures that his actors know everything about the inner lives of the people they are playing. This allows them to convey a raw authenticity.

Such was the filmmaker's exhaustive attention to detail, says Wang, that filming would stop while Mann decided to repaint the walls of a room, or ask a character to change his shirt a dozen times just to get it to look the way he wanted it. Then there was the punishing pace set by the 71-year-old director, which Hemsworth - who, at 31 years, is less than half Mann's age - found "exhausting".

"I was the most exhausted I have ever been. The shooting schedule was six days a week, with long, long days spent discussing the scene. At one point I was like, 'Haven't we talked about this? Haven't we done this? Again and again?' But by the end of it, I was almost addicted to that kind of pace," Hemsworth says.

Amid the hard work, "you also have a lot of fun working with him. Plus we were travelling the world and seeing Asia. Hong Kong was crazy, a mash-up of the new world and the old world, neon signs, technology, and doing things in the villages they did hundreds of years ago. It was awesome," he says.

Hong Kong is almost a character in the film. The visual highlights include sweeping aerial shots of the skyline at night, and action scenes which involve breakneck sprints through the narrow streets of Shek O. There's also a late-night dai pai dong dining scene that is tense and atmospheric.

Mann was thrilled by these scenes. "I have wanted to shoot in Hong Kong since 1979 when I was first there," he says. "To me, it's fabulous. It's so alive. It's exquisite visually and has very impressive civil engineering and infrastructure. But that also makes it difficult to shoot in. They have routed traffic and pedestrians in a way that works, and they don't want your movie company interfering with that," he says.

The film's action moves around Hong Kong, the US, Malaysia and Indonesia. Mann and his cast and crew spent 66 days filming in 74 locations in the four countries.

As Hollywood is trying to penetrate the mainland market, there may have been commercial factors at play in the decision to use Asian stars and locations. But Mann insists that there was no agenda beyond creating a truthful tale that resonated for him.

"I wouldn't be making a movie, and putting in this many years and effort - leaving home before my wife wakes up and getting home after she goes to sleep - because of marketing analysis," he says. "That's not why you do it."

Instead, when thinking about the cast of characters for Blackhat, Mann says he recalled a chance meeting he had in Venice a few years ago with a Chinese man "with a perfect American accent, who lived in Beijing, had always lived in Beijing. It was incongruous, and that become the model for Chen," he says.

"I was looking for somebody who was Chinese, educated at a US high school and Massachusetts Institute of Technology and who spoke perfect American English," says Mann. "I met Wang, who was born in Rochester, New York, lived in Taipei, and who said, 'I'm this guy'. He is so charming and precise. He's very well-educated, he's a classical violinist and a jazz pianist, and he has an insatiable curiosity and an amazing work ethic," says Mann.

Wang's character has a sister played by his former Lust, Caution co-star, Tang Wei. Mann describes the impact Tang had on him: "She walked into the room and said hello; her English wasn't great, but I knew she was the character. There was something volatile and candid about her manner, something impulsive and spontaneous.

"She's a brilliant actress and she's wonderful to work with. When she wasn't shooting, she was in her hotel room thinking about her character. That intensity was not a matter of discipline. She did it for the sheer pleasure of it," says Mann.

Tang and Wang believe that cinema's increased globalisation has opened more doors for talented performers from around the globe.

"I think it's better for everyone," the actress says. "For Chinese and Asians, and actors from Hollywood, too. They have the chance of doing better at the box office in China now."

Wang agrees, arguing that the notion of Chinese actors striving to break into Hollywood has been turned on its head. "We always talk about Asians breaking into Hollywood. But Hollywood is also thinking about breaking into China," he says.

Blackhat opens on January 22