James Cameron is now about two months into shooting the four Avatar sequels. The filmmaker has already alluded to the fact that the film will largely shoot underwater, but the big question on everyone’s lips is how that will affect the motion capture in the movies.

Cameron caught up with the folks over at Collider who brought up that very subject.

“Well, we’re doing it. It’s never been done before and it’s very tricky because our motion capture system, like most motion capture systems, is what they call optical base, meaning that it uses markers that are photographed with hundreds of cameras,” Cameron said.

So, shooting underwater sounds pretty difficult. He went on:

“The problem with water is not the underwater part, but the interface between the air and the water, which forms a moving mirror. That moving mirror reflects all the dots and markers, and it creates a bunch of false markers. It’s a little bit like a fighter plane dumping a bunch of chaff to confuse the radar system of a missile. It creates thousands of false targets, so we’ve had to figure out how to get around that problem, which we did.”

“Basically, whenever you add water to any problem, it just gets ten times harder. So, we’ve thrown a lot of horsepower, innovation, imagination and new technology at the problem, and it’s taken us about a year and a half now to work out how we’re going to do it.”

Cameron is reportedly training with the young cast on how to hold their breath underwater, a process that they have been doing for six months now. Now they’re reportedly all up in the two to four-minute range.

“They’re all perfectly capable of acting underwater, very calmly while holding their breath,” Cameron added. “We’re not doing any of this on scuba. And we’re getting really good data, beautiful character motion, and great facial performance capture. We’ve basically cracked the code. Now, we’re still working in our small test tank. We graduate to our big tank in January.”

The four Avatar films will be shot back-to-back over a period of a number of years. The first film will hit cinemas in December 2018.

More at the end of the link above.