Over the past year, 3-D has changed the business of Hollywood. Both of this year's top-grossing films – "Toy Story 3" and "Alice in Wonderland" – made most of their money from 3-D screenings. One-third of all box-office receipts in 2010 came from 3-D ticket sales, according to the International 3D Society trade group. And "Avatar," widely considered to be the paragon of 3-D films, returns to theaters at the end of August after already becoming the most profitable movie ever.
But has the extra dimension changed the craft of Hollywood? Proponents say that today's stereoscopic (3-D) technology is finally powerful enough to add not only visual depth but also emotional depth.
Phil McNally, the stereoscopic supervisor for Dreamworks Animation, admits that many 3-D movies have used the effect as a gimmick.
"Monsters vs. Aliens," which Mr. McNally worked on, had several flying-at-the-audience gag scenes. "Whereas I think everyone would agree that 'How to Train Your Dragon' and 'Shrek Forever After' have almost no stunt shots," he says. The 3-D effects are "almost all about the emotional content. And that's the kind of 3-D that really will live on long term."
For example, McNally used stereoscopics in this year's "Shrek Forever After" to ramp up the drama of a pivotal scene. Early in the story, the evil Rumpelstiltskin tricks Shrek into signing a magical contract, which propels the rest of the movie.
At the beginning of this scene, the 3-D effects are very subtle. Yet as Rumpelstiltskin manipulates the situation, the visual distance between him and Shrek increases. The background slowly slips further away and Shrek seems to drift closer to the audience. The characters are not actually moving, but McNally has dialed up the visual depth so that the viewers feel, perhaps subconsciously, as if something strange is happening.
The effect is similar to the way a soundtrack changes to match the emotional tenor of each scene.
Within a single shot, McNally says, the action can go from 50 percent depth – flatter than real life – to 150 percent, where the room balloons to an impossible size.
"Generally, you can think of the emotional intensity as increasing as they're moving toward us, frankly, more toward our personal space," McNally says.
Director Werner Herzog chose to film his next movie in 3-D for the opposite reason: He wants to look deeper into the screen. His documentary on prehistoric cave paintings, debuting in September at the Toronto International Film Festival, will use 3-D to evoke the cavernous feel of the Chauvet cave in France.
As filmmakers experiment, many stereoscopic tricks are still being hashed out. "Avatar" director James Cameron needed to rethink how and when he switched from one camera angle to another. Modern action movies often rely on quick cuts and a shaky camera to make scenes feel more frenetic: Think of James Bond or Jason Bourne. But that approach doesn't work well in 3-D. A viewer's eyes need time to adjust. If a 3-D film cuts too quickly, the audience may miss some of the action – or simply get a headache.
Of course, Hollywood recognizes that the current surge in 3-D titles isn't about emotional impact. Americans have shown that they'll pay more for a 3-D experience (see chart). That's why "Clash of the Titans" got a hasty 6-1/2-week conversion to 3-D – a move that even the president of the film's stereoscopic crew has said was done too quickly.
If slipshod business decisions get in the way of clever, effective 3-D, then the whole movement could erode, warned Mr. Cameron at the D8 technology conference in June. "It's really going to be incumbent on studios to put quality first," he says. "Otherwise the business model is not going to have longevity."