'Everest' cast worked through cold temps, high altitudes says director

HOLLYWOOD, Sept. 10 (UPI) -- Venice Film Festival headliner Everest wasn't just another CGI-heavy action movie, it was a drama shot on-location with truly shivering actors.

More than half of the Baltasar Kormakur-helmed film -- based on actual events outlined in Jon Krakauer's Into Thin Air -- was shot on location, he said. "Maybe two-thirds. But there were some impossible places that we had to build."

Shooting mainly in Nepal, Italy and the U.K., Kormakur and his actors -- including Jake Gyllenhaal, Josh Brolin, John Hawkes and Jason Clarke -- had to endure subzero temperatures while carrying their own equipment on mountainsides. Both A-listers and the crew slept in small lodges, ate local food and coped with low oxygen levels to get through the project.

"Basically, we walked as far as the insurance company would let us," Kormakur told Film Journal. "We go to the memorials [for climbers who died on the mountain], and that's when people started getting sick. We had to send for helicopters, it was an urgent, urgent evacuation for some."

When it comes to the cold, shooting in the Italian Dolomites brought temperatures close to 30 below zero, but Kormakur was encouraged by the environment. "Actually you can get pretty good performances out of those conditions," he said. "Actors just kind of deliver because they want to get out of it."

"And I think what's helpful is that I will stay right there with them, in the same conditions, show them what they need to do," the director continued. "So they are more likely to work with you than if you're sitting someplace warm and telling them, 'Keep going.'"

On top of the grueling conditions, the crew had to worry about mountain animals, like yaks. During one scene, the animals became spooked by a helicopter set to shoot footage. "[They] were not used to the helicopter," Kormakur told USA Today. "The yaks came running" for actress Naoko Mori, but a heroic Josh Brolin reportedly stopped the yak.

Everest, also starring Robin Wright, Michael Kelly, Sam Worthington, Keira Knightley and Emily Watson, opens in theaters Sept. 25.