3D: Coming to a screen near you

When the man behind the highest-grossing film of all time announced plans to make a $200 million sci-fi epic entirely in 3D, eyebrows raised across the industry. Family animations in 3D are one thing, but that kind of outlay on a film with narrow genre appeal and so few capable 3D cinemas? It would be a titanic gamble for any studio to take. But James Cameron isn’t merely a director. He knows 3D far better than most, and if he says its time has come, important people take notice.

“Watching a stereo movie is looking into an alternate reality through a window,” Cameron told Variety, before cranking the hype a notch further. “I believe that a functional MRI study of brain activity would show that more neurons are actively engaged in processing a 3D movie than the same film seen in 2D.” Such bluster comes easily to 3D’s chief evangelist, and if he has his way – which looks likely given the raft of demos at this year’s Consumer Electronics Show (CES) – 2009 will be the year 3D comes of age as an entertainment medium.

The signs are plain to see. Nvidia is working with games developers to build 3D directly into their latest releases, and with monitor manufacturers to bring it to your desktop. Cinema chains are rolling out 3D projectors across their theatres, while TV manufacturers progress from HD to 3D-ready sets. And then there’s Sky, buoyed by its booming high-definition service, announcing audacious plans to beam 3D to your living room via your existing set-top box.

Put simply, all parties agree that today’s 3D technology works. The glasses are more Matrix-chic than the red-and-blue specs of the 1980s, and the issues that plagued 3D in the past have been all but eliminated. So, just as HD has become the must-have upgrade, the industry is betting big on 3D being next.

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So what’s changed? Most people remember those red-and-blue anaglyph glasses and, while they couldn’t be further from the current state of 3D, the core concept still applies. To achieve any stereoscopic effect, each eye must be shown a slightly different perspective of an image to simulate the way we see things in the real world. If done with suitable accuracy the visual cortex of the brain is tricked into fusing the two images into one, resulting in the perception of depth. Anaglyphs achieved this with colour filters, but in recent times two more advanced approaches have been developed.

Polarisation is the simpler method: the left and right images are interlaced and displayed together on a special TFT, with a filter over the screen to polarise alternate lines at opposing angles. Corresponding lens filters on a set of cheap polarised glasses allow each eye to see only half of the image.

The more advanced and expensive method uses active-shutter technology: this doesn’t require a special filter on the TFT, but instead uses battery-powered glasses with liquid crystal shutters on each lens. As the two images are rapidly alternated tens of times per second, a transceiver synchronises the shutters in the lenses to open and close in time with the left and right images on-screen, so each eye sees only its intended image for half the frames in each second.