This video from Wired takes us through how they made the barrel scene in The Hobbit: The Desolation of Smaug with some amazing facts and figures like:
98 hours of footage was shot to make the seven minute scene
There were four days of filming on location
Three rivers in New Zealand were used
Eleven hours of aerial footage was shot
Production planning made 1091 preview shots
There was 35 hours of dry-set green-screen footage
And there’s more. Sit back and enjoy!