James Cameron has added two cast members to “Avatar.” Stephen Lang and Michelle Rodriguez will join Australian actor Sam Worthington, Zoe Saldana, Sigourney Weaver, Wes Studi and CCH Pounder in the performance-capture film, which is in production in Los Angeles. In October, the company will move to Wellington, New Zealand, close to Peter Jackson’s Weta Digital, which is supervising the film’s visual effects. Lang plays a seasoned Marine Corps colonel who travels to the faraway planet Pandora to take charge of its troops. Lang first met Cameron 20 years ago for a role in “Aliens” he didn’t get. But Cameron never forgot him. Rodriguez plays an ex-Marine pilot.