How that infamous bear attack scene in 'The Revenant' was made, and other secrets of the movie revealed

Director Alejandro González Iñárritu may have insisted on making his new movie "The Revenant," which came out Christmas Day, as authentic as possible - including having actors go through a week-long boot camp to correctly portray mountain men in the 1800s - but there was still some movie magic needed to pull off this gory revenge tale.

That's where legendary production designer Jack Fisk comes in. He's best known for the beautifully designed period settings in movies like "The Thin Red Line," "The New World," and "There Will Be Blood," over his three-decade career.

Here, Fisk reveals some of the secrets behind the making of "The Revenant," including how that now-legendary bear scene came to be.

Warning: spoilers ahead.