Hollywood is buzzing about 3D. Dreamworks Animation CEO Jeffrey Katzenberg has compared it to the introduction of color. Director James Cameron delayed the release of his stereoscopic epic Avatar in part to give theaters more time to convert to 3D capability. A dozen or more stereoscopic films will be released in 2009, and more than 30 movies are in production. But stereoscopic films are not a revolutionary concept; in fact, audiences have been paying for them since The Power of Love in 1922. The golden age of 3D was in the 1950s, with a brief resurgence in the 1980s. Each time experts heralded the format as the next big thing in filmmaking, and each time, the surge quietly subsided.

So what has convinced Hollywood that 3D is finally ready for its closeup? The short answer may be that technology has caught up with the concept. Stereoscopic films of the past were plagued by problems. "People always liked 3D," says David Cohen, an associate editor at Variety. "It just didn't work very well." The 3D format is now much more reliable, thanks to the introduction of digital technology and products developed by companies such as RealD, based in Beverly Hills, Calif., which spent 18 months combining stereoscopic science with digital projection. "NASA, the military and Fortune 500 companies use 3D to design automobiles and aircraft, because you need to see the way we see in real life—with depth," says Michael Lewis, who before founding RealD created content for 3D IMAX films. "Our goal was to come up with a simple technology that would allow us to get that experience to the world. Cinema, being at the top of the visual-food-chain experience, is where we felt we had to start."

The 3D Headache

Humans naturally see in stereo because our eyes, set about 2 in. apart, each see a slightly different view; our brains combine that data into one image, which allows us to perceive depth. The 3D format tries to replicate this effect by shooting with two cameras, one representing each eye. But it's not as simple as setting the cameras eye-width apart and yelling "action." The distance between the two cameras, or interaxial distance, determines the perceived depth of a scene, known as volume. "The wider you separate the cameras, the more 3D volume there is," says Phil McNally, global stereo effects supervisor at Dreamworks Animation. Shooting for a big screen and scaling down reduces 3D volume; shooting small and scaling up creates too much 3D, which is headache-inducing for viewers.

Filmmakers also need to calculate the zero parallax setting, or ZPS—the point where the two digital images converge onscreen. ZPS determines what appears to occur in front of the plane of the screen and what seems to happen behind the screen.

When 3D movies were shot on film, the potential for botched settings was huge because cameras had to be aligned by hand. But that was just the beginning of the problems with film. The cameras also had to capture a scene in perfect time with each other—which is impossible because even the movement of film through a camera causes distortion. In addition, the two rolls of film had to be matched precisely for color.

Projection in theaters was also problematic, since it was impossible to perfectly align the two projectors—again, one for each eye. Plus, film usually needs to be repaired during its life cycle, which created discrepancies between the two reels, resulting in films that were painful to watch.

As for the audience's role, filmmakers in the 1920s (and as recently as the 1980s) used overlapping red and cyan images—known as an anaglyph—to create stereoscopic movies. Audiences wore glasses with red and cyan lenses, which ensured that each eye saw only one of the two overlapping prints and allowed the brain to create a 3D image. Anaglyphs were originally designed for black and white, so using them on color film led to poor color representation. During 3D's golden age, in the 1950s, stereoscopic movies relied on linear polarization and polarized glasses, which funneled images to the proper eye by restricting light. Polarization created better colors, but if viewers moved their heads, they disrupted the stereoscopic image.

Digital Relief

Current 3D films, however, are subtle, immersive and easier to produce, thanks to digital technology. While some analog-era challenges still apply, filmmakers now use computers to determine interaxial distance and ZPS and to align cameras. Digital capture eliminates issues with inconsistent film stock, and if a filmmaker still bungles the job, new software can be used to digitally correct errors in postproduction.

Whereas two film projectors were once required to show 3D, theaters can now use a single digital projector outfitted with a photo-optical device; theaters are in the process of replacing analog projectors with digital ones. (According to the Motion Picture Association of America, 4632 of the more than 40,000 movie screens in the United States had digital technology in 2007.) The film industry will save $1.5 billion a year in print costs when it can send masters via satellite or fiberoptics, so it is partially underwriting the conversion: A digital projector and server cost a hefty $70,000.

The ability to show 3D movies, says Perry Hoberman, an associate professor at the University of Southern California's film school, is a huge incentive for theaters. Not only does the experience give people a reason to leave their homes and HDTVs, but theaters can also charge more for tickets. (Katzenberg has proposed adding an extra $5 to tickets for 3D films.) "For exhibitors," Hoberman says, "it's the first thing to come along that's a carrot instead of a stick to get them to convert to digital."

Even polarized glasses have been upgraded. Today, filmmakers use circular polarization, which retains 3D fusion while allowing audience members to move their heads. "After 10 minutes, 3D used to be a bad experience," Lewis says. "With new technology, it's a really good one."

Box office from the first films in this latest stereoscopic era shows that audiences are hungry for 3D. Disney/Pixar's Bolt, still in theaters at press time, earned approximately 41 percent of its $111 million domestic box office from 3D, which accounted for 27 percent of the film's screens. Journey to the Center of the Earth earned approximately 60 percent of its $102 million gross from 3D, which accounted for 30 percent of screens.

The home-electronics industry also wants to tap into 3D's popularity. At this year's Consumer Electronics Show, Samsung, Sony and Panasonic touted the format's home potential. "Panasonic does not think that 3D high-definition for the home is far away at all," the company's North American CEO and chairman Yoshi Yamada told reporters. In fact, a home-electronics group called the 3D@Home consortium estimates that 1.9 million 3D-ready TVs were sold in 2008. Panasonic is pushing an industry-wide standard for stereoscopic hi-def and has built a 3D Blu-ray disc-authoring center that aims to put stereoscopic DVDs in stores by 2010.

The potential goes beyond DVDs: The NFL and NBA have beamed stereoscopic broadcasts of games into movie theaters. "It's not often that I get this excited about something," says Glenn Adamo, vice president of NFL Media Operations, who supervised the 3D broadcast of an Oakland Raiders-San Diego Chargers game in December. "I hope we get to do it again."

When it comes to movies, one thing seems certain: The chances of 3D sticking around are better this time. "It's not a huge bubble like in the 1950s, when everyone scrambled to produce 3D movies and didn't know what they were doing," Hoberman says. "The format works pretty well; there has been investment in various systems, and studios are making money on it. It's not going away this time."

How it Works: 3D Animation

A stereoscopic movie consists of two slightly different views of the same action—one for each eye—which creates the illusion of depth. An audience wearing special glasses is able to see the heroine below jump into "personal space" (action that appears to occur in front of the screen), while the pursuing robot remains in "world space" (action that seems to take place behind the screen). Most studios plan to release upcoming animated films in 3D; here's how it's done.



Animation: Animators capture the action with stereo camera rigs they create in a computer. To ensure that no elements in a scene appear flat, filmmakers shoot with as many as three dual rigs. Commercial software and proprietary tools allow animators to precisely control what appears in personal space and world space, and where the different camera views coincide.

Projection: A single digital projector, outfitted with a photo-optical device, superimposes the two films—each with a different polarization—on a special silver movie screen that is capable of showing both 3D and 2D films. The projector triple-flashes each frame for each eye for a total of 144 frames per second—double the rate of regular cinema.

The View: Audience members wear glasses with circular polarization, which allows only one image into each eye by restricting light; the brain combines those images into 3D. The glasses also maintain stereoscopic fusion.