The digital world is essentially flat. Computers, TVs, movie screens, even cellphones, display images in two dimensions.
But several latter-day Columbuses are trying to chart a digital world in three dimensions. And they've made enough progress that 3-D imaging - once a laughable Hollywood experiment - is reaching new levels of realism.
Not only is 3-D making a comeback in theaters, it's seen as a legitimate tool to enhance the work of scientists, engineers, and advertisers.
Some of the first applications of 21st-century 3-D may be in security and military areas, where a 3-D image of a bag in a security scanner, a cargo container on a dock, or a ground target from a plane may help reveal what is otherwise hidden.
Best of all: Viewers won't have to wear those goofy red- and blue-tinted glasses, experts suggest.
People see the real world in 3-D largelybecause our eyes are separated just enough to view objects from slightly different angles. That gives our vision depth of field, also called stereoscopic or binocular vision.
In 1953, Hollywood tried to recreate the effect onscreen in "House of Wax," using multiple cameras whose images were juxtaposed. The horror film turned Vincent Price into a star, but the technique never quite crossed into the mainstream. Lately, thanks to improved technology, 3-D film is making a comeback.
Last Christmas, "Polar Express" became the first Hollywood movie to be released in 3-D on IMAX, the jumbo movie screens that have popped up around the United States and the world. It was the latest of nearly three dozen 3-D films to be shown in IMAX theaters since 1985. In March, Hollywood mega-directors George Lucas ("Star Wars") and James Cameron ("Titanic") endorsed 3-D feature films as the wave of the future.
Instead of expensive and complex filming using multiple cameras, new techniques now allow movies already shot with a single camera to be converted into 3-D, opening up a whole new library of existing material. After viewing a 3-D version of a clip from his original "Star Wars" movie, Mr. Lucas declared, "it looks better than the original."
These theatrical applications - as well as the familiar 3-D attractions at theme parks - still require an updated version of the old 3-D glasses. But a number of companies, from giant Toshiba Corp. in Japan to small start-ups around the world, are looking past that technique to create "naked eye" or "autostereoscopic" 3-D images.
The technique is "kind of like putting the glasses on the display" instead of the person, says Keith Fredericks, vice president for commercialization at Opticality Corp., in New York. Opticality sees an early application of its glasses-free 3-D system in advertising signs that "pop out" at passersby to grab their attention. This month the company is displaying a 180-inch-long "video wall" at Japan's National Museum of Emerging Science in Tokyo as part of a world exposition there. It's believed to be the largest naked-eye 3-D display ever built.
To viewers, some images appear to recede several feet into the sign while others pop out. As viewers move in relation to the sign, they see different views, just as they would with a real object, an effect known as "motion parallax." "That really increases the realism," Mr. Fredericks says.
LightSpace Technologies in Norwalk, Conn., uses another 3-D technique to create what it calls a DepthCube. Images are projected from the rear of 20 screens layered one in front of the other. At any given moment, each screen can be clear or reflect an image. By projecting images onto the screens 20 times faster than the ordinary rate of video projection, the eye sees a single image with a sense of depth behind the screen, as though the viewer were looking into a fish tank.
LightSpace forecasts the first big market for naked-eye 3-D will be for computer terminals, not movie theaters. The company's staff already plays the video game "Doom" in 3-D on its screens. "Those scenes when you're looking down a hallway are profoundly deep in this kind of a display," says Alan Sullivan, the president and CEO. "It's great."
Fredericks also sees huge movie screens, TVs, hand-held games, even cellphones using the new 3-D technology in the future.
Beyond fun and games, the US government is interested in 3-D X-ray machines at airports, Mr. Sullivan says. With a 2-D view, an object such as a knife can be missed if it is oriented to show only its thinnest side to the camera. With a 3-D view, security personnel could quickly rotate the image and recognize the knife from a different angle.
Glasses-based 3-D often causes eyestrain, since the eyes are trying to focus both on the flat screen, where the image is really being created, and on the nearer illusion of the object as well, Sullivan says. That's why these effects are usually shown only for brief periods in theaters and amusement parks. "You wouldn't want to sit there designing a new automobile or evaluating molecular designs that way," he says. The DepthCube creates no such problem because viewers look at images that have real depth, he says.
The technology is "pretty impressive," says Harry Goldstein, a senior associate editor at IEEE Spectrum magazine, the trade publication for electrical engineers, which published a cover story on the new 3-D by Sullivan this month. "You get a sense of heft to the objects," says Mr. Goldstein, who has visited Sullivan's lab. "The sense of space and depth is incredible."
Soon, computer monitors may have a feature that switches the monitor to 3-D view, or 3-D may be built into elements of the operating system itself, Fredericks predicts. It might be used for anything from taking an on-screen walk through a house for sale to analyzing a strip of DNA.
The ultimate in 3-D would be a true video hologram, such as the holographic message from "Princess Leia" depicted in the first "Star Wars" film. The image could be seen from any angle, both horizontally and vertically.
"We're not quite there with real holographic images projected into the air yet, but we're definitely moving very rapidly in that area," Fredericks says.
The problems are considerable, though not insurmountable, Sullivan says. For example, a 20-inch-wide flat video screen might have perhaps 1,200 pixels, or points of light, per horizontal row. A hologram would require 1 million pixels per horizontal row. Multiply that by the million pixels needed per vertical row and the display would contain 1 trillion pixels, far beyond what today's technology can produce. And that doesn't include the as yet unavailable computing power needed to make the image move in a realistic way.
"It's unclear to us in the industry as to how you might actually make that," Sullivan says. "We constantly think about what we could do to skin that cat, to solve that ultimate of 3-D challenges."