Stellan Skarsgard has said making the film Nymphomaniac was educational.
The actor starred in director Lars von Trier's raunchy drama, in which Charlotte Gainsbourg played a nymphomaniac recounting her erotic antics to a stranger, played by Stellan.
Speaking at the Venice Film Festival - where a director's cut is screening - the actor revealed he had learned a few things from the movie.
"I know a little more about female sexuality, but it's still a mystery," he said.
"On the other hand, my own sexuality is also a mystery."
Stellan has worked with Lars before and said he agrees "to everything he asks me to do" because working with the filmmaker is so much fun.
"It might not always be pleasant watching his films, but that's different," he said at a news conference for the five-and-a-half-hour film.
The actor said he agreed the moment the director called him and said "Stellan, my next film will be a porno film and I would like you to play the male lead."
"Who could resist an invitation like that?" he said.
Lars was banished from the Cannes Film Festival three years ago for saying he could sympathise "a little bit" with Hitler.
Afterwards, the director said he would no longer speak in public, and didn't attend the Venice news conference. Instead, Stellan phoned him with journalists' questions and then relayed the answers.