After years in the film-industry doghouse, 3D (the illusion of depth seen by the viewer) is back with a vengeance. Paramount Pictures' decision to bring Beowulf director Robert Zemeckis' animated take on the old English epic poem to 3D as well as regular movie screens was seen as something of a gamble. After all, this is a technology that reached its most recent peak with a spate of poorly performing sequels in the 1980s - witness Jaws 3-D and Amityville 3-D - that many studios would rather forget. But Paramount's wager has paid off. More than 40 per cent of the US$28 million in revenue Beowulf scooped up in its opening weekend in the United States came from 3D ticket sales, even though 3D screens account for only 20 per cent of the total number of screens. Given Beowulf's success, the trickle of 3D films now on offer is expected to turn into a torrent. A number of high-profile projects, including Avatar, a sci-fi opus from Titanic director James Cameron, and a Steven Spielberg-backed version of the adventures of Belgian comic-book hero Tintin, are already in production. The extra dimension has received additional credibility with animation giant Dreamworks' recent pledge that all its releases from 2009 onwards will be in 3D. This may sound eerily familiar to readers old enough to remember the format's earlier incarnations - shoddy red and blue glasses and all - but the technology has moved on. In 2005, Disney's Chicken Little became the first film released in the digital 3D (or Real D, the name of the technology used and its main corporate backer) format, which looks set to become the next industry norm. Like standard 3D, the digital version requires viewers to wear polarised glasses, which give images the illusion of depth by controlling the amount of light that reaches the eyes - but that's where the similarities end. While traditional 3D employs two projectors to beam separate polarised images onto movie screens, the digital version uses only one, which throws out images destined alternately for the left and right eyes at lightning speed. This gives digital 3D pictures a smoother, more continuous look and allows them to occupy a wider segment of the viewer's field of vision. The more sophisticated circular spectacles used for Real D viewing also do away with the splitting headaches - confirmed by a recent visitor to one of Hong Kong's three 3D-screen cinemas - that were a frequent byproduct of wearing the old 3D lenses for a couple of hours. Real D predicts its technology will be installed in 5,000 theatres globally by 2009. The company is not alone in championing a return to 3D. Canada's Imax has a proprietary 3D format to treat audiences to what the company bills as 'the most immersive cinematic 3D ever created'. Most 3D films will hit both Imax and digital 3D screens, as Beowulf did, but given the high cost of Imax systems - the giant screens come with a US$250,000 price tag - digital 3D may have the advantage. The race to define the next generation of cinema doesn't stop there. Select theatres in Japan have already started to debut '4D' movies, which combine 3D visuals with smell, touch or other sensory effects. Imagine seeing Saw in 4D: a headache might be the least of one's problems. Beowulf is showing in 3D at the UA Imax cinema in MegaBox, Kowloon Bay.