This summary does an injustice to the originality and the sophistication of Tregenza’s way with narrative form. Unlike many intricate stories, there’s nothing puzzle-like about the complex drama of “Fast”: there’s nothing snippety or cut-to-fit about its expansive and extensive scenes. No scene has more than a half-dozen actors, most have one or two, and Tregenza films their interactions—including long solo walks—in near-constant motion. Tregenza, now seventy-five, has developed his extraordinary technique through the course of his long but grievously intermittent career, which started, in 1988, with “Talking to Strangers.” Tregenza worked for many years as a film professor, and, since 2007, has been at Virginia Commonwealth University, in Richmond, in and near where “Fast” was filmed.