SAN DIEGO -- Matt Damon made his inaugural trip to San Diego Comic-Con, where he gave Hall H attendees the first extensive look at Sony's still-in-production epic "Elysium."

On Friday, when MTV News caught up with Damon, he revealed the two biggest reasons he signed on for the dystopian film: "District 9" and "Avatar."

As many fans know, the actor was once in talks to star in James Cameron's 3-D blockbuster, but a little movie called "The Bourne Supremacy" got in the way.

"I was dying to do 'Avatar,' " Damon said. "I was dying to work with Jim Cameron, but I just couldn't; it was a scheduling problem. I literally couldn't do it without kind of ducking out of the last 'Bourne' movie before it was really done five years ago. And so, morally, I couldn't do it."

But the actor's hunger to dive into a richly devised sci-fi world never waned. "I remember saying to my wife, 'Wow, these movies don't come along [very often].' A really big sci-fi movie where somebody creates a totally unique world but you know the performances [will be great]. Jim Cameron is a great example because he's directed some of the best scenes within movies. Like that scene in 'The Abyss' where she has to drown herself, and they have that realization. It's just like so harrowing and brilliant."

"Elysium" is set in a future where the poor are left to toil away on an increasingly overpopulated earth while the rich have absconded to a lavish space station. Damon's working-class character is exposed to radiation at his job and given five days to live. A group of underground criminals outfit him with a cool exoskeleton that allows him to stage an infiltration of the space station. ("District 9" 's Sharlto Copley stars as one of the film's villains.)

So when the chance came along to headline Neill Blomkamp's follow-up to "District 9," Damon dove in headfirst. He told the Hall H panel that he would've even said "yes" to a simple cold call from the writer/director, without first hearing any details about the story. Luckily, Blomkamp came prepared with meticulously detailed notes, from the backstory of his futuristic setting to the various armaments and equipment involved.

"When I saw 'D9,' I felt like, 'Man, this guy, he's created this world that I recognize but I've never seen before. And yet it's performance-based too. Those performances are really good. He clearly knows how to work with actors. This is really great,' " Damon recalled. "And so when this kind of fell into my lap, there was no way I was going to turn it down."

The Hall H footage was filled with unfinished visual effects but the stunning visuals -- shot largely in Mexico City and reminiscent of the classic "Mad Max" movies and, of course, "District 9" -- wowed the audience just the same.

"Elysium" is due in theaters March 1, 2013.

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