Rehearsal for director Robert Eggers’ “The Lighthouse” wasn’t as long as Robert Pattinson remembers.

“I’ve never rehearsed like I rehearsed with Robert before,” Pattinson said at the first screening of the period thriller on Sunday morning. “We rehearsed for what, three weeks?”

Actually, no — it was only one week!

“One, but it felt like three to you,” Eggers said.

The black and white movie chronicles two men (Pattinson and Willem Dafoe) who slip into madness while tending a remote lighthouse.

“It was kind of nice to have that pressure cooker of an environment,” Pattinson said. “We were just in a little room in a hotel in Halifax and there’s something about being contained in there, and not really showing anything, [that] built up pressure for the shoot. That was kind of an interesting environment to work in.”

The actual shoot in Canada proved to be grueling as well.

“We shot on the southern tip of Nova Scotia on this peninsula volcanic rock, Cape Forchu,” Eggers explained. “We built a 70-foot working lighthouse that could shine for 16 miles…Forchu was a very unforgiving place. There are no trees and the wind is relentless.

“The wind could be blowing so loud that I couldn’t hear Willem and Rob if I was standing this far away from them,” Eggers said while almost face to face his two stars. “And, I think we wouldn’t have had the believability of the atmosphere and the environment of the storm if we weren’t actually shooting in it. There’s many scenes where you might think we have wind machines and rain machines and we don’t. I mean we used them, too, but often times the most crazy dramatic moments were photographed for real.”