How times have changed. When “Glitter,” a dreadful, and mercifully forgotten, vehicle for Mariah Carey, appeared shortly after 9/11, the fact that its NYC exteriors contained brief glimpses of the World Trade Center caused a considerable stir, with many arguing that showing the fallen towers was disrespectful. Now Robert Zemeckis has used all the CGI wizardry at his disposal—and that’s a lot—literally recreating the structures in Imax 3D, looking more impressive than ever. And people will undoubtedly respond with warmth at the vision of the magnificent structures, especially since the director uses them for a moment of almost prayerful reverence at the close.

Unfortunately, one can also use the towers to raise a cinematic question. Would they have been as impressive if they were 37 stories high rather than 110? One can introduce that question because “The Walk” is about one-third of a good movie. The last forty minutes are masterfully crafted and, for the most part, exhilarating. But the first eighty are, to be honest, pretty awful. How should one calculate its overall quality?

The film is, of course, an account of the 1974 feat of French wire-walker Philippe Petit, who—helped by a few co-conspirators—surreptitiously strung a cable between the nearly-completed towers and famously proceeded back and forth across it one fine August morning, defying the authorities but entrancing citizens on the sidewalk below and the millions worldwide who were later informed of the stunt by news media.

The story of Petit’s daredevil accomplishment has previously been told on screen, in James Marsh’s remarkable 2008 documentary “Man on Wire.” Without entirely ignoring the back story, Marsh presented the tale as essentially a caper movie, and succeeded in engendering an amazing amount of suspense from an event that was already in the public consciousness. By contrast Zemeckis and his co-writer Christopher Browne, using Petit’s memoir “To Reach the Clouds” as a basis, spend a good deal of time on the funambulist’s life in France prior to coming to New York—material that proves less than scintillating—and surprisingly don’t manage to extract nearly the same degree of tension from the actual walk, even with all the technical tools at their disposal, as Marsh did with his recreations, which depended more on suggestion.

The first two-thirds of “The Walk,” like much of the rest, is narrated by Joseph Gordon-Levitt, who as Petit tells the story in the man’s typically exuberant voice while perched atop the Statue of Liberty’s torch overlooking the towers. He goes back to his youth, explaining how as a boy he became entranced by circus wire-walking and undertook to teach himself the skill. His obsession led his frustrated father to toss him out of the house, and eventually took him to Papa Rudy (Ben Kingsley), a master of the art, to teach him the tricks of the trade. Going to Paris to work as a street performer, he met Annie (Charlotte Le Bon), a musician who became his girlfriend and prime helper, and after successfully managing a walk between the spires of Notre Dame Cathedral, fixated on the idea of his World Trade Center coup. Eventually he enlisted two other collaborators—photographer Jean-Louis (Clement Sibony) and Jean-Francois (aka Jeff) (Cesar Domboy), a mathematician whose English was poor and was acrophobic to boot, and the quartet was off to New York.

This portion of the film is frankly disappointing. Even those who have admired Gordon-Levitt’s work in the past are likely to find his strenuously puckish take on Petit, however true to life it might be, grating at best and insufferable at worst. His French-accented English is also an irritant (though not quite as much as Kingsley’s indecipherable one). But certainly the fact that he does a mime routine at one point takes things off the charts. For this fine young actor, “The Walk”—especially in its initial stages—represents an audacious choice but a career stumble.

That’s as much Zemeckis’ fault as Gordon-Levitt’s, of course: the director-writer, never noted for his subtlety, here goes overboard in striving for whimsy and elfin charm, and the prodding of his star in that direction has an unfortunate effect. The impact is almost as negative for Kingsley, though at least he’s helped by minimal screen time and lesser expectations. The rest of the cast handle themselves more pleasantly in the French section of the picture, with Le Bon, Sibony and Domboy all coming across agreeably.

Though Gordon-Levitt remains somewhat hamstrung by the character’s flamboyance even when the action moves to New York, the movie itself takes off. Some energetic new characters are added, most notably James Badge Dale as a fast-talking electronics clerk and Scott Valentine as an insurance agent with a convenient office high on one of the towers. But they’re secondary to the narrative arc, which takes all the conspirators into the tricky business of getting their equipment up to the tower roofs, eluding security personnel in the process, and then rigging it up for the walk. In truth, Marsh extracted more suspense from these machinations despite Zemeckis’ use of special effects to generate some big moments—especially those while Philippe and Jean-Francois are trapped on a girder in an elevator shaft—and the blaring score by Alan Silvestri, which sounds as though it was composed for a 1970s heist movie. Domboy, however, really comes into his own in these scenes, though how Jeff miraculously overcomes his extreme fear of heights at this crucial moment is never really explained.

But then the action moves to the walk itself, and it proves spectacular, with the cinematography by Dariusz Wolski employing every trick in the current CGI playbook to endow those twenty minutes or so with a real sense of wonder, especially in the big screen format with its smartly-used 3D possibilities. Gordon-Levitt finally breaks free of the stiflingly chipper requirements of the part and shows the genuine physical grace he’s capable of. Unfortunately, the near-incessant narration continues and the depiction of the cops trying to coax Petit back to the ledge is often crudely stereotypical, though Silvestri’s score calms down some. Whether you consider the post-1974 epilogue, with its virtual paean to the fallen towers, appropriate recognition of a national tragedy or an attempt to play on viewers’ emotions is an open question.

So the question is whether the outstanding 30% or so of “The Walk” is enough to salvage the rest, and the opinion from this quarter is, unfortunately, no. As “Man on Wire” demonstrated, this is a great story, but Zemeckis’ film proves an overly cute retelling of it, and except for the walk itself it’s more a cinematic misstep than a triumph.