Any indie filmmaker with talent who decides to direct a Cassavetes-style drama is hardly being unoriginal, for his was not a series of films so much as a philosophy of cinema. The challenge for a Cassavetes scholar isn't figuring out how to remake Shadows, but how to employ certain types of artifice (e.g. improvisation, unprofessional acting, and rule-breaking camerawork and editing) to create something more real. Chalk is the latest such exercise for director Rob Nilsson, whose Cannes-winner Northern Lights (1979) launched a career that's remained admirably uncompromising through coarse features like Signal 7 and Heat and Sunlight. The story of two pool-shark brothers (one shoots, the other hustles), Chalk was conceived through scripting and acting workshops with Nilsson's Tenderloin Action Group, comprised of volunteer filmmakers and homeless residents of inner-city San Francisco. The result is a compelling and unpredictable character study that, building very slowly to a climactic pool match, also satisfies the rules of the game--and it's all the more inspiring to independents for being a convincing work of cinema verite that was shot on video. Nilsson, named an "adopted Minnesotan" by U Film, will introduce the screening. Bell Auditorium, Saturday at 7 p.m.