So why should anyone who’s not a design buff rush to this movie (opening this week in New York and Philadelphia) instead of, say, the new “Matrix”? Because the backstory of Louis Kahn is as powerful, messy and heartbreaking as any screenwriter could devise. The film opens with Kahn’s obituary–he died alone, bankrupt, in the men’s room of Penn Station, New York, on the way back from a trip to India. His body lay unclaimed for three days. Though he had a wife and daughter back home in Philadelphia, he led a clandestine life–working all hours, often sleeping in his office–and, unbeknownst to most of his circle, he had two children out of wedlock, by two colleagues. Kahn’s magisterial buildings (such as the Kimbell museum in Ft. Worth) have the power of ancient monuments, and the undercurrents of his private life are as old as time. In this moving, surprisingly sympathetic portrait, his son weaves the public and the personal together as gracefully as a skater gliding toward infinity.