Effervescent and freewheeling, Francois Truffaut’s “Jules and Jim” (1962) still crackles with life, a pure bolt of lightning from the arthouse pantheon. Now that it’s been unveiled in a new print for a weeklong run at Film Forum, the eternal love triangle — set in Paris and Germany before and after World War I, suspended between idyll and apocalypse — seems scarcely to have aged.

“Jules and Jim,” a landmark of the French nouvelle vague, was, of course, a prime artifact of the 1960s emergence of “the cinema” made by the former film critic whose previous “The 400 Blows” was a line in the sand for the French film industry. Along with his sidekick Jean-Luc Godard (“Breathless”), among others, Truffaut changed the rules of the game. He reinvented the reel.

What’s appealing is how “Jules” still resonates with that improvisatory zeal. It defies translation into some inevitable, fusty museum piece. Perhaps considered a tad risqué at its time, it was adapted by Truffaut from Henri-Pierre Roché’s memoir-like novel, which he had discovered as a 21-year-old perusing the bargain bin at a flea market. Spare change and providence can never be underrated. The 75-year-old author’s fictionalized memories of youthful indiscretions were lent renewed vigor by the filmmaker, who offered the story of two dandies — the Frenchman Jim (Henri Serre) and the Austrian Jules (Oskar Werner) — in love with the luminous and liberated Catherine (Jeanne Moreau).

Though the movie’s title would become a kind of code for “ménage a trois” during the soon-to-be-swinging ’60s, and is continually referenced in other movies, the film itself is nearly chaste: more philosophy than bedroom. And, yet, oh so arousing.

The role of Catherine was a signature one for the now legendary Ms. Moreau, around and about whom the camera flutters and stutters like a racing heartbeat, then breaks into elegant stride, keeping pace not only with the kinetic Catherine as she races ahead of her swains along the Seine, but also chasing the perfect moment, a little delirious, a lot in love.

A good part of the film’s charisma is due to Ms. Moreau, whose Mona Lisa smile incarnates for her lovers an actual goddess, one whose bohemian restlessness makes her easy to obtain but hard to hold. And it is even more difficult, for the film’s idealistic Renaissance men, to uncover her as somehow fully mortal, so caught up as they are in the sublime airs of romance. Catherine’s gamine playfulness can yield quickly to bridge-leaping dramatics, as Jules and Jim — art-addicted café mongers at heart — argue over Baudelaire’s notion of woman as untamable vixen, and scamper fecklessly in her wake. Truffaut could not have picked a better actress to vex the weaker vessel that is man, yet the film’s greatest pleasure is in watching how the director so completely realizes his vision.

The movie is packed with technique, as if Truffaut intended to show off the full range of his rapidly growing mastery, like a childhood runt who had become a muscleman and could not wait to get to the beach. It had not even been three years since “The 400 Blows” (1959) and its documentary simplicity, and here its director was all but doing handsprings with the camera (actually managed by cinematographer Raoul Coutard): voice-overs, subtitles, superimpositions, wipes, freeze-frames, collages, gliding crane shots, leisurely tracking shots, jump-cuts, and giddy 360-degree spins.

The circular shots, so blissfully unbound, are one of the most notable aspects. Early on, when a café tart named Thérèse accompanies Jules home, she woos him with her “choo choo,”inverting a cigarette in her mouth and blowing smoke like a locomotive as she chugs around the bedroom. Not much later, the same girl abandons Jules at a bar, luring a new lover with the same schtick as the camera whirls again to find Jules sharing a table with Jim, sketching a woman’s face on its round surface.

It’s a charming motif that has spawned scholarly essays, and it’s symbolic of the film’s embracing good will: “Jules and Jim” may be the friendliest tragedy in the history of movies.

Through December 21 (209 W. Houston St., between Sixth Avenue and Varick Street, 212-727-8110).