It started as just another concert film, but as Katy Perry's marriage to comedian Russell Brand unraveled, her new documentary transformed into what she called a "warts and all" depiction the pop star is happy to show her fans.

Katy Perry: Part of Me, which debuts in 3D on Thursday, is anything but standard fare. Most performers wouldn't dare show fans what they look like first thing in the morning without makeup, or worse, doubled over bawling backstage in costume. But Perry insisted that everyone see.

"I'm OK with showing what's behind the curtain," Perry, 27, told Reuters in a recent interview. "I'm OK with showing that side of me because it helps people relate (to me) better and think of me as a human being."

On its face, the movie chronicles the singer on her first world tour in 2011, but as the year played out, Katy Perry: Part of Me chronicled the demise of her marriage to Brand, whom she wed in 2010. By December 2011, they had split and in February, they divorced.

The film shows Brand early on, happily visiting Perry backstage and picking her up in his car.

But soon he disappears from the story, and Perry suffers emotional breakdowns and fits of crying while her team of handlers seems helpless.

The movie humanizes Perry in a way that is rare in Hollywood. In fact, Perry's success has been based mostly on an almost cartoonish image of herself with over-the-top outfits featuring cupcakes and lollipops.

She sings pop songs such as "California Gurls", "Last Friday Night (T.G.I.F.)" and "Teenage Dream". Perry has sold 11 million albums worldwide.