Everyone warned Elizabeth Banks against filming the outdoor concert finale for “Pitch Perfect 2.” It was June in Baton Rouge, La. It was scorching hot, it was hurricane season, and they would have to build a full, functioning stage and recruit a small town of extras to make it believable.

But Banks knew what she wanted.

“I kept saying, ‘I don’t care, it’s going to look cool, we’ve got to do it’,” said the actress, producer, and now, feature director.

It took nearly a month to build the Glastonbury Festival-inspired stage. As for the extras, the production sent out an open invitation casting call to fans of “Pitch Perfect.”

More than 3,000 people showed up.

The massive undertaking required four all-night shoots, multiple cameras, elaborate performances and a tolerance for mysterious bug bites. Banks even took responsibility for the crowd’s waning energy.

“At one point, she went out on stage and started whipping them into a frenzy,” said Banks’ husband and producing partner, Max Handelman. But the crowd really lost it when she brought a few Bellas out, too.

“It was her connecting the fans with the girls and letting everyone know that this was a big deal,” Handelman said.

It’s no secret that “Pitch Perfect” has fans to spare. Universal Pictures’ modest 2012 comedy about a college a capella group (the Bellas) racked up $113 million worldwide and an additional $103 million in home video sales.

As plans for a sequel started to take shape, though, the first film’s director, Jason Moore, signed on to the Tina Fey-Amy Poehler comedy “Sisters,” and suddenly “Pitch Perfect 2” needed a director.

Banks, known for roles in “The 40-Year-Old Virgin” and “The Hunger Games,” had been thinking about directing for some time. She directed plays at the University of Pennsylvania, and had been taking on small projects over the past few years to learn as much as she could. Plus, as a producer and actor on the first film, Banks already knew the a cappella world and had the trust of returning cast like Anna Kendrick and Rebel Wilson.

“Right as I was raising my hand to do it, the studio said, ‘Why don’t you do it?’” she said.

The Bellas, this time, are trying to claw their way back to the top after a high-profile embarrassment.

“I certainly did not plan for my feature directorial debut to be a giant musical,” she laughed. But she dove in and endeavored to make everything — costumes, performances and stakes — bigger. There’s even a cameo by “Pitch Perfect” superfans the Green Bay Packers.

“I feel that I have more to offer this business and that I was being underused,” Banks said of directing and producing. “I knew it would probably change my life. I also knew that I had to say yes. Women just don’t get offered these opportunities.”

For the over four-months-long shoot, Banks relocated to Baton Rouge with her husband and two sons and “lived like a monk.” She put in her 12-hours on set, spent as much time with her children as possible, and slept.

“I’m a wonderful multitasker ... as are most moms that I know. That helps,” she said.

She also drew on the teachings of directors she’s worked with — how Judd Apatow gets improv coverage, how Francis Lawrence films dancers (include the hips) and how to stay calm on set. On “Catch Me If You Can,” Steven Spielberg was “so relaxed.”

“What you realize is that he has the best in the business on every department working for him. What’s he worried about?” she said, and made it her goal to do the same.

“She puts in the work. She’s extremely prepared. She takes it extremely seriously,” marveled Handelman. “There was not a single person asking ‘what does this first time director know? What does this actress know?’ She had 100 percent control of a crew that was like 90 percent men.”

Although Banks acknowledges that she likely exceeded everyone’s expectations, she’s also quick to put it in perspective.

“I wasn’t performing brain surgery. No one’s lives were in my hands ... particularly. I’m not dodging bullets in Afghanistan. We’re just making a fun movie. It should be fun. If it’s not fun, you’re making it harder than it needs to be,” she said.

Acting remains a priority for Banks, who laughed that as of the film’s May 15 release, she doesn’t have another job lined up. Discussions about a third “Pitch Perfect,” for Banks, will come later.

She’s also eager to direct again, even though the ideal conditions of “Pitch Perfect 2” would be hard to replicate.

“I wouldn’t be surprised if she’s a bit contrarian in her next choice,” said co-producer Paul Brooks. “She likes raising her own bar.”