Break ups suck. That's a universal fact. Filming intimate love scenes for a movie in front of strangers with cameras? Any working actor will tell you that's no fun. But filming a sex scene in a comedy with your high profile, real-life ex? That's cruel and unusual punishment, no?

Turns out former couple Justin Timberlake and Cameron Diaz certainly struggled through filming a sex scene in their new comedy, 'Bad Teacher,' out tomorrow, but it was not as weird as you might think.

The film's director Jake Kasdan called it the "most uncomfortable sex scene in history," reports PEOPLE. In history? There's a lot of sex scenes in the canon of film, so that's a big overstatement.

Still, we don't doubt that it was all kinds of awkward, especially since JT and Cam's four-year relationship, which spanned from 2003 through 2007, was very public, as were their PDAs and their not-so-nice split, which found him rebounding with Jessica Biel on the quick.

Kasdan said that discomfort aside, the former couple are still fond of one another. "I guess the real truth is that they're good friends … They're buddies," he said.

Diaz and Timberlake are not only buddies. They're professionals. "They got in there and started doing it," said Kasdan. "And it was so funny, we just couldn't stop shooting it. And we were doing it almost the whole day. And really crying, laughing at the [video] monitors."

Diaz, 38, agreed about the weirdness of shooting the scene, saying, "Yes, yes. It was just [an] absurdity, a form of hilarity for all of us involved. We went to work that day and said, 'What time do we start being ridiculous? … Eight o'clock? Perfect."

Kasdan didn't have to go to extreme measures or sweeten the pot to get JT, 30, to commit to a film with his A-list ex. He revealed, "I'd say, 'Cam, what do you think of this?' And she said, 'It's a great idea.' And then we went and said, 'Justin, come do this,' and he said, 'Yeah, let’s go.'"

Watch the Trailer For 'Bad Teacher'