James Cameron was like a “kid in a candy store” on the set of Avatar.

Actress Sigourney Weaver - who stars as Dr Grace Augustine in the new 3-D animated blockbuster - said watching the director helm his first movie in 12 years since the epic Titanic was incredibly rewarding.

“He invented the cameras, he was using the cameras. He was shooting his characters in the flora and fauna he created with the creatures that he created. He was having a great time, and so were we. To see him on the set of Avatar was like watching a kid in a candy store.”

James - who spent four years producing the movie - used revolutionary CGI techniques that required the actors to work wearing a camera fitted to a helmet, which picked up their facial expressions. The 60-year-old Hollywood star said the director managed to create a “magic” on set.

“When we were in our little suits with our ears and tails we could see what we looked like in Jim’s magic camera - I don’t know what he calls it, I call it the magic camera - so we were free just to be with each other as actors, as characters and Jim’s focus was completely on us.”