Writer/director Ron Krauss ran through more than a few Hollywood starlets in trying to cast the homeless pregnant teen, Apple, in his debut feature film — "Gimme Shelter." He'd spent more than a year getting to know such women and those who ran the Several Sources Shelters in New Jersey, the project had become a cause to him and he had to get this casting right.

"Finally, I sent a video link to some girls staying in a shelter and they looked at several auditions," Krauss recalls. "They didn't know the young women auditioning. The girls didn't know 'High School Musical.' And they picked Vanessa Hudgens."

Hudgens, the former Disney Channel sweetheart, might have seemed an odd choice for the frumpy, pierced and pregnant runaway in search of a father she never knew. "Hollywood people I told went, 'That Disney girl? Are you crazy?' " Krauss says. But Hudgens, at 25, has been putting those Disney years far behind her with films as gritty, edgy and R-rated as "Sucker Punch," "Spring Breakers" and "The Frozen Ground."

"There's nothing cooler than looking into a mirror and not seeing yourself," Hudgens says. "The scripts that you get are always similar to the last project somebody saw me in. But that just means that I want nothing to do with it. I like variety. I don't like being stagnant, sticking with the same thing."

She won't come right out and say it, but after a few years of "sweet girl" roles after the wildly popular "High School Musical" ended, movies such as "Beastly" and "Bandslam," Hudgens has set her mind to doing more adult roles in films that demolish that old image.

"Sucker Punch" saw her as an inmate in a mental institution whose escape is envisioning herself (and her fellow inmates) as scantily clad hookers avenging themselves on the evil men in their lives. "Spring Breakers" put her in another ensemble of young women behaving badly. "The Frozen Ground" showcased Hudgens as a teen prostitute who survives a serial killer attack.

For "Gimme Shelter," Hudgens whacked off her hair, gained weight, wore piercings and "lived in a shelter for three weeks," Krauss marvels. "I never thought a Hollywood actress could play this role, that the movie star would show through. But she had swagger to her, she can hide her beauty. She was showing a part of herself she's never shown before."

"Gimme Shelter," which is based on a true story and uses real shelters and girls staying in them as its backdrop, offered the actress the chance to work with James Earl Jones (as a priest) and Ann Dowd as the firm but compassionate operator of the shelter Apple winds up in. It's the sort of indie film where "You get to push yourself out of your comfort zone," Hudgens says. "It's work, but it's work that's fun. It's the sort of thing you look for in order to grow."

"Gimme Shelter," which opened last weekend, comes out at a time when poverty is back in the national conversation. It's being embraced as a faith-based film, as the shelters it is set in are Catholic sponsored and abortion is never a seriously considered option for a pregnant teen with no home, no job and few prospects. Hudgens says she embraces the messages of the movie, "a script that had a lot of courage about it, I think. You've got abortion and child abandonment and homelessness and abuse. Tough subjects."

But after this latest walk on the dark side, Hudgens was ready to mix things up again for her next picture. She knows she may lose her longtime fans, alienating some as she tries to reach that broader audience that leads to career longevity. Her next film, "Kitchen Sink," is about a time "when zombies and vampires and humans are trying to coexist in peace," Hudgens says, laughing.