James Cameron has admitted shooting for 'Avatar 2' is still only in the test stages.
The hotly anticipated sequel to the Oscar-winning 2009 fantasy film has already had its release date pushed back several times due to the challenges of shooting motion capture under water, where the sequel is set.
Now, the 63-year-old director has told movie website Collider.com that successfully shooting a full scene underwater was only achieved last week.
James said: "We've done a tremendous amount of testing, and we did it successfully, for the first time, just last Tuesday (14.11.17). We actually played an entire scene underwater with our young cast. We've got six teenagers and one seven-year-old, and they're all playing a scene underwater.
"We've been training them for six months now, with how to hold their breath, and they're all up in the two to four minute range. They're all perfectly capable of acting underwater, very calmly while holding their breath. 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."
Earlier this year the production was forced to announce it would not be completed in time for its previous release date of December 21, 2018.
And the 'Titanic' director has revealed he doesn't expect to finish test stages until January 2018.
He said: "Now, we're still working in our small test tank. We graduate to our big tank in January. There's a tremendous amount of water work across 'Avatar 2' and 3. It's ongoing into 4 and 5, but the emphasis is on 2 and 3."
Following the huge success of epic space adventure 'Avatar' - which starred Zoe Saldana, Sam Worthington and Sigourney Weaver, and was nominated for nine Oscars - James set about writing the sequels, insisting he wanted to shoot them underwater.
But he admitted water has been his enemy.
He said: "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.
"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."
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