Charlotte Gainsbourg has admitted that filming Nymphomaniac wasn't easy.
The British-born actress reunited with filmmaker Lars von Trier for the third time for the raunchy drama, in which she plays a nymphomaniac recounting her erotic antics to a stranger, played by Stellan Skarsgard.
"It wasn't easier. I knew him better, but it didn't mean it was easier," she told Empire.
Charlotte - who previously worked with the director on Antichrist and Melancholia - went on: "The shooting was really long. It was very, very intense.
"With Antichrist a lot of the intensity came from the suffering. In this one, the difficulties ranged from the physical scenes to the talking parts with Seligman (Skarsgard). That was a big, big challenge - so many words! We couldn't memorise it all."
But Charlotte revealed she was fine with the sex scenes.
"As long as I knew that porn actors were going to perform the sex, I knew I'd be safe," she said.
"I could even keep my knickers on. Everything was happening in post-production."
The 42-year-old admitted she couldn't believe it when Lars approached her about the role.
"I thought he was making a joke when, at the press conference in Cannes, he said his next film was a porno with Kirsten Dunst and me," she said, although Kirsten doesn't appear in the film.