In the end, however, logistical issues mandated that Pau take on the role in this epic fantasy action-drama, which he initially joined as co-producer and photography and special visual effects director but also went on to co-direct.

Three years in the making, tells the story of a hot-headed demon slayer, the beautiful icy demon who beguiles him, and a powerful artefact he steals from hell for the good of humanity. As one would expect of a production that bears Pau's imprint, the film looks impressive, with visual effects used in 77 per cent of the scenes.

While Pau has more than 50 cinematography credits, this mainland-Australian-US co-production is only the fourth film he has directed. His most recent directorial effort before this, 2002's , also made use of computer-generated imagery (CGI) and other visual effects but on a much more modest scale than this US$26.4 million budget production.

" was very good practice and a lesson for me because we were using a very small amount of money to do something that was incredible to do," Pau says with a laugh. "I learned from that movie that the post-production really needs time and money - that was a painful experience.

"Even though still didn't have enough time in post-production, at least we had 10 months to finish. If we'd had two more months, yes, the result would have been better even with the same amount of money."

This time around, he also engaged the services of several respected special effects companies. "Not only was Weta Workshop [the New Zealand company that worked on Peter Jackson's trilogy] involved, but I also hired 12 Hollywood-grade CGI artists in every field to help Macrograph, the Korean company, finish 1,200 shots for us in a short period of time." He says.

"Also we hired Pixomondo, the company that did to do the full CGI running on the rooftop sequence and the battle scenes underwater."

Pau talks with particular pride about "the love shot" in which Zhong Kui (portrayed by Chen Kun, who also is one of the movie's executive producers) and Snow Girl (played by Li Bingbing) intertwine in mid-air.

"That was a one-of-a-kind shot that runs one minute and 20 seconds, [involving] about 2,000 frames of CGI. It's unprecedented in Asian cinema, history-making," he enthuses. However, he denies the film's copious visuals are mere eye candy conceived primarily for the filmmakers to show off their technical abilities.

"The film needs special effects, because if we want to broaden the horizon of the story and not be limited to just the human figure fighting, we need to make the impossible possible," he says. "The visual effects become a necessity - they become part of the language of the film. We need to think wider about how to tell the story rather than how we do it traditionally."

In the 21st century, it would be too boring to portray the main character as yet another heroic martial artist, he decided. "I thought Zhong Kui should be transformed into another figure in order to do something that's impossible for humans to do. That's why we use CG form rather than a human in a costume" whenever Zhong Kui goes into fight mode.

And this even though he had been impressed by how appropriate for the part Chen Kun looked when in costume and with make-up on to make him look far less handsome than in real life!

Creativity also came into play when deciding on what story the film was going to tell about the character from Chinese folklore, whose legend has been disseminated orally over the centuries, Pau says.

There have been many tales associated with the legendary vanquisher of demons and evil spirits; Zhong Kui is said to have 80,000 spirits under his command and is so ugly that even ghosts are afraid of him. He also became known as a protective deity in Chinese culture, so families traditionally put up drawings of Zhong Kui on their doors during the Lunar New Year to ward off ghosts and bad spirits.

Having signed on to the project as the film's scriptwriter, co-director Zhao Tianyu ended up working on 20 drafts of the script with a number of other writers. In all, six people share the writing credits for a story that envisages Zhong Kui as a lover as well as a fighter.

Although Pau didn't get his way as to who should play the Jade Emperor, he was able to build a romantic component into this superhero fantasy. He strongly believes that injecting some romance into Zhong Kui's life helps to make the character more three-dimensional. "Also, the romance sets up the opposition" that is needed to add tension and allow for the insertion of intriguing plot twists into the story, he says.

Pau has worked on a number of Hollywood productions, including Ronny Yu Yan-tai's (1998) and 2007's . Although some might see that as a dream come true, he felt restricted by that industry's dogged adherence to strict filmmaking formulae and a preference for films to be mono-genre.

In contrast, during his student days at the San Francisco Art Institute, Pau had been encouraged to be creative. "Our teachers always inspired us to think 'Why not?' So when I think of a theme I need to portray, I want to do something different. I'm always inspired by the words 'Why not?' Why do we have to do something that people already did?," he shares. Why not try to make the impossible possible?

And with that goal in mind, he set about making a multi-genre film with groundbreaking visuals, exciting action scenes and heartwarming romantic moments geared to melt even the coldest of hearts.

opens on March 12