The Clash meant so much to so many people for so long that it's almost impossible to imagine how the group must have looked from the inside. They were a punk band with passion, politics, and - it seemed like a paradox at first - dignity; consequently, the usual tell-alls and reunions have never been their style.

So director Julien Temple has done it for them - or more specifically, the group's late figurehead and leader - in the bighearted generational bear hug of a movie "Joe Strummer: The Future is Unwritten." Suffused with clear-eyed affection for its subject and times, this is not your little brother's punk documentary, patiently explaining who did what when. Rather, it's a gathering of the tribe to memorialize one of their own who was also one of our best.

The "gathering" is literal. Late in his life, Strummer was given to organizing impromptu campfires, utopian meetings of the mind to disseminate music and political thought. Temple honors that by filming most of his interviews around midnight campfires in New York, Los Angeles, and London. At first it feels like a filmmaker's annoying affectation (especially since none of the talking heads are ever identified), but the gimmick takes hold, and by the time we get to Bono, hair whipping in the wind and sparks as he speaks of how the Clash completely reoriented his teenage years, we've entered a very special place.

Temple was documenting the punk scene as early as 1976, and he has access to an astounding trove of material both public and personal. The result is that "Joe Strummer" plays like a time-capsule collage, constantly tossing up audiovisual surprises and new ways of looking at things. Because the director interviewed him so often over the years, Strummer's voice is constantly in the mix as well. At times you get the eerie sense of a dead man narrating his own life story.

The throughline is chronological, starting with the youth of a boy born John Graham Mellor - a diplomat's son whose early years hopscotched from one international posting to the next (already he was more cosmopolitan than most of his safety-pinned peers). Playful home movies give way to clips from "Animal Farm" and Lindsay Anderson's "If . . ." to illustrate the brute realities of British public schools.

Along the way, Mellor discovered Woody Guthrie, British ska, world music records (via his father's diplomatic pouch), the Rolling Stones, and US proto-punk acts like the MC5; he joined up with bands called the Vultures and the 101'ers and changed his name, Dylan-style, to reflect his lack of guitar-picking skills. By the time the Clash formed, so had Joe Strummer, and so had his mission: "Authority was something to be avoided and, if possible, attacked."