The biggest, most expensive sci-fi epic of all time is back in theaters Friday. Avatar will arrive at the multiplexes and Imax theaters again this weekend, where it will go up against new releases The Last Exorcism and Takers.

The rerelease contains nine minutes of additional animated footage, a heady incentive sure to draw ticket buyers spellbound by Avatar's groundbreaking visuals back to the box office.

But the reason for the return voyage to Pandora isn't purely about profits – Avatar has already pulled in a mammoth $750 million at the domestic box office since it began its initial run in 2009, and sold 19 million DVDs since April.

Rather, director James Cameron tells Wired.com the original release was shorter than he originally wanted.

"I wanted to reinstate the créme de la créme of what was taken out," he says.

"We had 45 to 50 minutes of various scenes at various stages of the cutting. There was a bit of pressure that we impose on ourselves because we didn't know how long audiences could watch a 3-D movie. We were pretty conservative and we cut pretty deeply."

Cameron argues that the original 161-minute running time did not deter people from wanting to see more. "Thirty percent of people said that it was too long, but most of the feedback we got was that they could stay longer. Nine minutes is an eternity in the editing room, but it's just 6 percent of the running time. The motivation was for me to see the picture finished."

Fans of Cameron's extended cuts, including the ones for Aliens and Terminator 2: Judgment Day, know that added scenes often include well-rounded subplots and back story. For example, in the extended cut of Aliens, we learn the character Ripley has a daughter who died, motivating her motherly relationship with the child Newt. How much should Na'vi fanatics expect within nine minutes?

"You'll see a little bit of background, a little bit of stuff that happened off camera in the movie that you saw – like the sturmbeest hunt falling within Jake's training of becoming a Na'vi," Cameron says. "And there's a scene that shows the missing step between the escalation of the Na'vi and the humans. There's a night attack scene and the aftermath the following day. You'll see new creatures, new set pieces, new emotional scenes. It's anecdotes, but it's not going to be perplexing or change the story."

Still, the definitive version will be released on Blu-ray in November with three cuts of the film – the original theatrical release, the nine-minute extended version hitting theaters Friday, and a cut with 16 minutes of additional footage. "Before I go to make another Avatar movie, I don't want to have to go back. When we close this box, it stays closed, which is why the one in November is the definitive version," Cameron said.

In order to add the scenes for the second theatrical release and the upcoming Blu-ray package, Cameron says, "I had to go back to Fox and say that I needed X million dollars." The additional scenes were "at template level," meaning they were cut before effects studio Weta Digital was able to provide the photo-like quality that initially drew people to the box office.

While Avatar is getting the big push this weekend, Cameron, true to form, is looking far ahead into Pandora's future with at least two sequels. "I'm actually mapping this out. One of the things that I'm working on is the novel, which is a good companion to the first movie."

Originally slated for a Christmas release, Cameron says it will now come out in 2011. "To me, the book is laying the foundational bed for the entire world and all of the back story and future history. There's definitely going to be a second and third film. I don't know if that means it's going to be a trilogy."

However, Cameron will first be acting as a producer for the 3-D adaptation of H.P. Lovecraft's At the Mountains of Madness with Pan's Labyrinth and Hellboy director Guillermo del Toro at the helm.

Cameron has told me in the past that he is not passionate about producing.

"Well, yeah, then Guillermo came along," he says. "In this particular case, I'm working with Guillermo because I enjoy his company, and a creative collaboration is something that we've talked about doing for a long time."

The news is beyond exciting for Lovecraft, del Toro and Cameron enthusiasts. What's even more exciting is hearing Cameron talk about their collaborative vision.

"It's going to be an epically scaled horror film and we haven't seen anything like that in a really long time – I guess since Aliens."

Like the novella on which it's based, the film will take place in the Antarctic, where humans encounter a race called the Ancient Ones. "The thing about Lovecraft is that he left a lot to the imagination," Cameron says. "He never told you what they looked like. He managed to create a sense of creeping horror without specifics."

Cameron believes that's what makes del Toro the perfect man for the job.

"Guillermo brings an eye for design that is so original and so quirky and so steeped in the lore of movie design and horror design, but always fresh and unexpected. Frankly, I just want to see what he comes up with and I want to enable the nuts and bolts of the production so he doesn't have to worry about that. I want to help him how to work in 3-D."

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