Vanessa Hudgens' hair nightmare

Vanessa Hudgens is still coming to terms with her shorn look after cutting off her long locks to play a homeless mum-to-be.

The High School Musical star ditched her glamorous look to play a dishevelled, pregnant tomboy with piercings in new film Gimme Shelter - and she admits the make-under was tough to take.

The 22 year old says, "It's really intense. I'm still getting used to it. I play this girl who's, like, homeless and she doesn't really care about her look... I kind of look like a boy throughout the whole movie.

"In the beginning my character cuts her hair and we were cutting it and it didn't look like I was cutting it myself, so I grabbed the scissors and started cutting my actual hair.

"I miss it (hair)... My sister is, like, my best friend and she naturally has, like, the longest hair, so whenever I'm around her I'm giving her the evil eye."

But that wasn't the toughest part of the filming process - Hudgens also had to give herself a pregnancy test on camera, and her character's labour was on film.

She adds, "There was no shame... I had to do a pregnancy test strip on film, which it was kind of awkward with the whole pulling the pants on and the stick... I didn't actually pee in front of an entire crew. I would not be OK with that... It was really interesting."