Riding Giants was directed by Stacy Peralta, who attended the screening

Redford, founder of the independent film festival, was among those at the screening of Riding Giants, from director Stacy Peralta.

"We're here because we love what we do, and it's the thrill of doing what we do that gives us such pleasure," he said.

The festival, which runs until 25 January, is showing 255 films including Redford's new thriller The Clearing.

This year marks the 20th anniversary of the festival.

It is featuring a raft of other long-awaited films. Friends actress Courteney Cox-Arquette stars in November as a photographer who struggles to cope after her boyfriend is shot dead.

Other entries include We Don't Live Here Anymore, starring Mark Ruffalo and Laura Dern in the story of a man's affair with his best friend's wife.

Introspective films

Kevin Bacon and his wife, Kyra Sedgwick, play alongside hip-hop artist Mos Def in The Woodsman, about a convicted child molester trying to rebuild his life.

Thirteen of the 16 entries in the dramatic section are directors' debuts, according to US website Variety.com.

Festival director Geoffrey Gilmore said many of the films made since the 11 September attacks on the US were more introspective, and featured characters unsure of their identity.

"The audience is not sure what the characters' search is really for, but all of those are outward searches and not inward. It's about trying to find one's place in the world and not one's self," he said.

Mario Van Peebles' Baadasssss! will be shown at the festival

The Sundance list includes several films made by African-American directors, including Vondie Curtis Hall's Redemption, the true story of a gang member giving up violence.

Mario Van Peebles' Baadasssss! tells the story of his father Melvin's 1971 film, Sweet Sweetback's Baadasssss Song.

Organisers said they were expecting a busy year after the success of the 2003 event.

"Of the major acquisition festivals of 2003, including Cannes and Toronto, Sundance was by far the busiest," said Tom Ortenberg, head of film releasing for distributor Lions Gate Entertainment.

Musical acts holding concerts in Park City during the festival include hip hop star Nelly, soul diva Macy Gray and singer-songwriter Jason Mraz.