To think it might take an animated film, with her playing a fiesty redheaded teenager, for the world to discover the wonders of Kelly Macdonald.

The Scottish Macdonald, 36, is already on HBO’s “Boardwalk Empire,” and already known to discriminating film fans thanks to “Trainspotting,” and “No Country for Old Men,” and to kids from her work in “Nanny McPhee.” But the animated “Brave” brings with it Pixar fame, and Disney princess immortality.

Macdonald was a “Snow White” fan as a child, and remembers a cherished “Sleeping Beauty” coloring book, but Merida, her character in “Brave,” “is quite a change from the other Disney princesses, from what I can tell. She knows her mind, knows what she wants and she isn’t interested in finding a prince and singing a song about it.”

The Glasgow native joined her fellow Scots Billy Connolly and Craig Ferguson for “Brave,” and Oscar winner Emma Thompson, “who’s half Scottish,” Macdonald adds, plays the mother of Merida, an archer-princess who isn’t sitting still for her mother’s lectures about duty, and how she must marry a chosen member of one of the other Highlands clans to keep the peace.

“I was a disgruntled teenage girl, so I certainly have that in common with her, as will any girl,” Macdonald says of Merida. “Merida may be Scottish, but she could be from anywhere a girl can speak her own mind and determine her own destiny.”

And for the first time in her career, Macdonald, a mother herself, gets to play a genuine big screen role model.

“Merida’s an awesome role model,” she says. “She learns all her lessons by herself. She doesn’t need someone to lecture her, to tell her what to do. She makes some bad choices, but then she makes things better by correcting those choices. And all this learning she does makes her come out the other end stronger and more self-confident. She’s a great character.”

Macdonald first made her mark in “Trainspotting,” “where she brushes off [fellow Scot] Ewan McGregor with an almost lyrical delivery,” notes Reed Martin, author of the indie film production guide “The Reel Truth.” “She’s confident, self-reliant, unflappable, and adorable which gives her a strong and wide-ranging appeal. “

The Irish actor Cillian Murphy, an old friend, former London neighbor (Macdonald moved back to Glasgow after getting married) and her co-star in 2003’s “Intermission,” says “Kelly is the most honest of performers. It never feels like acting with her. She just ‘is.’She’s just luminous on screen. But there’s a warmth and vulnerability to her that you can see in her face and sense in her voice”

Macdonald is more modest about her range, referring to Merida in “Brave” as “probably tougher than any character I’ve ever played. More vibrant and vital and adventurous. She’s so physical that I never would have been cast if they’d shot this live action. They’d never think of me that way.”

But she’s still happy to have had the chance to play the tough teen, to star in a movie about a girl who fights to choose her own fate.

“I had my ‘choose your own destiny’ moment. I left home at 17 to become an actress. But I never had big arguments about that with my mom. She was always very supportive, determined to let me make my own decisions.

“I haven’t gone out of my way to avoid being typecast, but it’s just sort of happened. But being Scottish, it’s nice to play a redhead, every now and then. And if you’re doing it in a movie for Pixar and Disney, you know that’s how people are going to really remember you.”