Lets take a look at five of the many technological innovations that James Cameron employed in his upcoming sci-fi epic 3D film Avatar.

Performance Capture Workflow: A lot of the film was captured using a performance capture technique similar to that of which Robert Zemeckis filmed Beowulf. So Cameron developed a virtual camera which will allow his to point it at his actors and see them as their computer generated characters in real time.

Simulcam: A camera set-up which allows them to follow or monitor a virtual character which was captured in performance capture into a live action environment in real-time. It also allows them to see what a virtual backgrounds will look like in a live-action shot. I know that Steven Spielberg had a set-up like this on A.I., but I think it only showed him wireframes of buildings, and was very glitchy. My impression from Cameron’s quotes is that the new technology renders something a lot more visual, probably akin to a video game (likely more last generation).

Facial Capture Head Rig: The actors in performance capture suits also wear a camera rig on their heads that takes digital shots of the actor’s face. This allows the computer generated character to have 100% facial movement, even in the real time performance capture workflow mentioned above.

Facial Performance Replacement: In traditional filmmaking they use ADR (or additional Dialogue Replacement) when filmmakers need a cleaner take of the actor’s dialogue, or need to fudge in a new line. But with a traditional film, you really need to trick a shot to make it work. The lips don’t always match up, and sometimes, if you’providing an entirely new line of dialogue, filmmakers usually resort to a wide shot or a behind the head shot, so that you can’t see the lips of the actor on screen. Since 60% of Avatar is performance capture, he has designed a way to insert a new facial scan/dialogue capture on an existing performance.

Fusion 3-D Camera System: The Fusion 3-D camera system was co-developed by James Cameron and and Vince Pace. The rig uses two Sony HDCF950 HD cameras to create stereoscopic 3-D. Cameron first used the system on his 2003 IMAX film Ghosts of the Abyss. It has since been used by Robert Rodriguez on Spy Kids 3-D and The Adventures of Sharkboy and Lavagirl, and most recently on Hannah Montana and Miley Cyrus: Best of Both Worlds Concert and Journey to the Center of the Earth. But I’m not exactly sure what improvements Cameron made to the rig over the last five years.

Read more about some of the technological challenges of the production on THR.com. Avatar will hit theaters on December 18th 2009.