"We spent a lot of money and a lot of time — almost five years — completely revamping our technology. It was very innovative. Then we started production, and I promised the actors, I said, 'Play it as close as you want; we will see it. We will see microscopic changes in your expressions that you may not even be aware of. You don't have to act bigger because it's performance capture. What you want to do is act closer, like you're in a tight close-up in a movie,'" he says, adding that the actors were actually in close-up shots at all times once they put on the head-mounted rigs.

"What they've found is that it's best to just be honest and truthful in the moment, just like they're talking or interacting with the other actor, fully in character. It all worked. I think, for those of you who saw the film, you know what I'm talking about. Those (alien) people are real; you believe they're real," Cameron explains.