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…