Cumberbatch's Hobbit work unveiled

Benedict Cumberbatch's face is covered with white dots in the motion capture video from the Hobbit films

Benedict Cumberbatch's motion capture performance as dragon Smaug in The Hobbit films has been revealed in a behind the scenes video released online.

The Sherlock star is shown lying on a platform in the middle of a film studio in a motion capture body suit, his face covered in white dots to pinpoint the movement in his face, which is then transferred to the computer generated image of the dragon in The Hobbit: The Desolation Of Smaug.

Benedict is snarling the lines in which Smaug threatens Bilbo Baggins, the hobbit hired by Thorin to help the dwarves reclaim their stolen kingdom and gold.

He growls: "Well, thief! I smell you. I hear your breath. I feel your air. Where are you?"

Even the actor's fingers have motion capture equipment on, which were transformed into claws for the finished film.

Benedict revealed: "You kind of have to imagine yourself into a vast creature in a huge space when you're really crawling about on a grey bit of carpet."

Director Peter Jackson said of the casting "We were looking for an actor who was not just going to voice a dragon that we would imagine.

"We wanted someone who would do something original and unexpected, something that was a surprise to us."

The video was released as part of the movie's extended edition, which goes on sale in November and is now available for digital download.