On Friday, Aug. 21, audiences will get a chance to see an extended preview of Pandora, James Cameron's fictional new cinematic world. IMAX theaters across the country will show 16 minutes of footage from Cameron's 3D, photo-real CGI sci-fi epic Avatar, out Dec. 18.

Demand for tickets to screenings caused Fox's website to crash on Tuesday. The footage—sandwiched between showings of Harry Potter and the Half-Blood Prince—will be a combination of what thousands saw last month at Comic Con as well as new, never-before-seen footage.

Avatar is the story of wounded ex-Marine Jake Sully, who is paralyzed from the waist down. To participate in the Avatar program, he travels to Pandora, a planet rich in biodiversity and exotic creatures and home of the 10-foot-tall, blue-skinned Na'vi tribe. There, Sully inhabits a human–Na'vi hybrid avatar, which gives him the ability to walk again. But as humans exploit Pandora's resources, and Sully falls in deeper with the Na'vi natives, he must choose a side in the epic battle that will decide the planet's fate.

Cameron first conceived Avatar 14 years ago, but couldn't film it at the time because the technology to create his vision wasn't available. He was finally able to begin four years ago thanks to advances in animation, motion-capture and camera technology—some of which he brought about himself. Cameron filmed the movie using the Pace Reality Camera System, a stereoscopic rig he developed with Vince Pace. The system allowed the director to shoot in 3D, with actors in motion-capture suits and to see their CG counterparts in the landscape of Pandora. Cameron's goal is to make the characters, the terrain and the creatures of Pandora—all computer-generated—look photo-real. From the footage debuted at Comic Con—which producer Jon Landeau promised was "just a small slice" of what we can expect—it looks like he's off to a good start.

For those who didn't get tickets to the 16-minute previews, which begin at 6 pm, never fear: A teaser trailer is now available online. —Erin McCarthy