Robert Luketic sheepishly says he thinks the South by Southwest film festival is taking a gamble on him by showing his Las Vegas thriller, “21,” on opening night.

“It’s an honor – it’s a big honor,” said the Australian director, whose first feature was the Reese Witherspoon hit “Legally Blonde.” “I’m not known for making movies that open film festivals. … We all took a risk with this one so it’s nice to have someone else like it.”

Based on the true story of a group of MIT students who won millions by counting cards at blackjack tables across Vegas, “21” will premiere on Friday night at the festival in Austin, Texas, before its March 28 theatrical release. The festival, now in its 15th year, runs through March 15.

Luketic probably doesn’t need to worry – his film is a perfect fit for the crowd of up-and-coming filmmakers and young audiences that tend to populate SXSW, says its producer, Matt Dentler. That was obvious last year when the Judd Apatow comedy “Knocked Up” played to a raucous reception three months before it hit theaters, helping create buzz not just for the film but for South by Southwest as a place where big Hollywood fare can thrive alongside smaller, independent offerings.

“We were really lucky with ‘Knocked Up,'” Dentler said. “We rolled the dice and said, ‘This is a film we think is really funny, let’s do something big with it,’ and it kind of blew up and got big out of the festival and that was really great. I think it helped us prove ourselves to Hollywood as a viable venue for a lot of these films, and by ‘these films’ I mean films that maybe appeal to a younger demographic.”

Along the same lines, South by Southwest will show the stoner sequel “Harold & Kumar Escape From Guantanamo Bay” from New Line Cinema; Paramount’s “Stop-Loss,” starring Ryan Phillippe as a soldier ordered back to duty in Iraq; and Universal’s “Forgetting Sarah Marshall,” another relationship comedy from the Apatow machine.

On the documentary side, there’s Martin Scorsese’s “Shine a Light” about the Rolling Stones; “Lou Reed’s Berlin” from Julian Schnabel, the Oscar-nominated director of “The Diving Bell and the Butterfly”; “Gonzo: The Life and Work of Dr. Hunter S. Thompson” from Alex Gibney, who just won a best-documentary Oscar for “Taxi to the Dark Side”; and “Where in the World is Osama bin Laden” from “Super Size Me” director Morgan Spurlock.

Also on the schedule are discussions with Helen Hunt, who will be at the festival with her directorial debut “Then She Found Me”; “Harold & Kumar” stars John Cho and Kal Penn; Billy Bob Thornton; and former Disney chief Michael Eisner, who will be interviewed by Dallas Mavericks owner Mark Cuban in what could be a riveting clash of the titans.

“At the same time, a lot of the other programming that’s not Hollywood stuff is further establishing us as a place where unique, innovative independent filmmaking can get a big boost,” Dentler added. “The documentaries and narrative features by young twentysomething filmmakers – there are a lot of films that have developed a real critical mass, especially within the blogosphere and the hipster-cred side of indie film.”

Several young filmmakers who took baby steps in this business at SXSW are returning with their first features. “The Pleasure of Being Robbed” comes from director Josh Safdie, who’d previously shown shorts there and who developed friendships that helped him in making his first feature-length film. With “Yeast,” the entire cast and crew consists of people who met at the festival.

“That’s what South by Southwest provides is that sense of community and collaboration. … For me, that’s so much more gratifying than late-night bidding wars and distribution deals,” Dentler said. “People come here and see each other’s work and they hit it off, get along, and four or five months later they’re making a movie together, and four or five months later they’re premiering the movie at South by Southwest.”

Luketic will be among them, making his first visit to Austin before jetting off to promote “21” at the annual ShoWest convention of theater owners in – where else? – Las Vegas.

Though he mainly has romantic comedies on his filmography – besides “Legally Blonde,” there’s “Win a Date With Tad Hamilton!” and “Monster-in-Law” – he says the “21” is truer to his artistic sensibilities. The movie stars Kevin Spacey, Jim Sturgess, Kate Bosworth and Laurence Fishburne.

“My second-year (student) film was about a serial killer in a trailer park on the southern tip of the Australian peninsula,” he said with a laugh.

And shooting in Las Vegas on the floor of the Planet Hollywood casino – during broad daylight, at peak hours – provided some thrills of its own. Luketic described it as “harrowing,” but it was crucial to telling this story the right way.

“I loved the fact that so many people get their (butts) kicked in Vegas, and this was finally a story where it’s the other way around. I myself have lost a lot of money in that town so I was fascinated by how they did it. We were very upfront about this in the movie: It does take a brilliant mind. They really were walking Pentium chips,” he said. “I was attracted to how these math nerds almost became rock stars. They inherited the keys to Sin City.”