Pleased to meet me: Sam Worthington contemplates the genetically engineered alien body he will soon inhabit in James Cameron’s “Avatar.”

James Cameron has been in the woods for a while. It’s been a dozen years since Titanic, though he has completed a couple of largely unnoticed deep sea documentaries — which were mostly exercises in developing 3D filming technology — in the intervening time. More importantly, it’s been nearly 20 years since he made a science fiction adventure flick, the genre he towered over with just a handful of classics from 1984’s Terminator to 1991’s Terminator 2. Having spent fully the most recent third of his life not making the kind of movies that made him famous, it would be easy to assume he lost his knack somewhere along the line. With Avatar, the director makes an emphatic statement that he hasn’t missed a step. He was just saving it up for something huge.

The story, which has been famously rattling around Cameron’s head for most of those years, looks 150 years into Earth’s future, after we’ve exhausted most of our own natural resources and must begin taking them from other worlds. The world is Pandora, and the resource is “unobtainium,” the purpose of which is never fully explained except to say that it is unbelievably valuable. This really isn’t important for any reason other than to bring humans to this world, where they are welcomed by the indigenous “savages,” the tall, blue-skinned Na’vi.

In order to gain acceptance within the native community (and rape their planet), human geneticists have managed to engineer Na’vi bodies that can be linked to specific human brains, allowing humans to infiltrate Na’vi society within these “avatars,” while their own bodies slumber back at the base camp. Jake Sully (Sam Worthington), a paraplegic marine thrust unexpectedly into the avatar program by circumstance, inadvertently finds himself a “chosen one” to the Na’vi tribe who live atop the richest store of unobtainium on the planet.