Much of what we see from the Earth-like moon of Pandora, the fantastical setting for the "Avatar" franchise, comes from a soundstage in Los Angeles, where scenes from the second and third movies were filmed. "We had to build an ocean," director James Cameron said. "We could make a two-meter swell. We could make a wave crash up on a shoreline if we built the shoreline."

Sigourney Weaver, Zoe Saldaña and other actors shot their underwater scenes in the nearly 250,000-gallon tank. Digital artists then took those shots, called performance captures, as a template to render the final versions of the characters we see on screen.

"So, performance capture, we use a whole bunch of cameras to capture the body performance of the actor," Cameron explained. "And we use a single camera (or now we use a

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