“Being a father.” That was director Matt Ross’s biggest influence in bringing Captain Fantastic to the screen. Best known as an actor who plays steely types such as tech exec Gavin Belson on HBO’s Silicon Valley and corrupt Mormon sect leader Alby Grant on Big Love, Ross was at the Sundance Film Festival with his sophomore directorial effort, this one about a counterculture dad of six who wrestles with returning to everyday society following his wife’s suicide. Viggo Mortensen, who knows a thing or two about playing dads in perplexing circumstances after A History of Violence and The Road, plays the title character here. In this clip from Deadline’s Sundance hub at the Samsung Studio, both Ross and Mortensen reflect on how fatherhood shaped the film. eOne acquired Captain Fantastic‘s U.K., Canada and Australia/New Zealand territories back in August. Bleecker Street will release the film this summer in the U.S. Today is the final day of the Sundance Film Festival.