7/23/2009 in Fifteen minutes of the big gamble sci-fi epic will be released for free in August. Tom Helberg James Cameron ("Titanic") revealed 25 minutes of footage from his 3D flick, "Avatar," at Comic-Con, Thursday. Attendees at the annual pop culture festival won't be the only ones to see an early preview of the film. In a very unusual move, 20th Century Fox will release 15 minutes of the film on August 21 on Imax and 3D screens to generate buzz for the upcoming film. The screenings will be free, [Reuters](http://www.reuters.com/article/entertainmentNews/idUSTRE56N0RT20090724?pageNumber=1&virtualBrandChannel=10522) reports. The epic sci-fi feature is set in the 22nd Century on the moon Pandora, whose inhabitants are the ten foot tall, blue humanoids called Na'vi,. A paralyzed Marine played by Sam Worthington volunteers to be transformed into a human/Na'vi hybrid, an Avatar. Stakes are high for Fox. The picture has been in development for four years and the budget is rumored to be anywhere from $200 - $300 million. Plus uncommon for big tent pole pictures, the story is an original idea by Cameron, not a remake or based on another property. Tom Rothman, co-chairman of Fox, even introduced the footage at Comic-Con, who said, "Moments likes these are rare for a movie company." "Avatar" opens in the U.S. December 18.