There's an automatic desire to embrace "The Polar Express" as translated to film by Robert Zemeckis. It is, after all, a story that holds a magical place in readers' hearts. And, thankfully, every detail of the beloved children's classic is meticulously reconstructed in the film, with visuals that can only be described as wondrous. To not adore it is to feel like a scrooge.

Drat that Chris Van Allsburg for not writing a longer book.

Based on Van Allsburg's award-winning Christmas story, "The Polar Express" is the tale of a young boy who is confronting that most terrible of revelations: A friend has informed him that "there is no Santa," and now doubt plagues his once all-believing mind.

And so on Christmas Eve, as the boy listens anxiously for the reassuring sounds of Santa's arrival on his roof, he is instead greeted by the loud hiss of a steam engine. As he tiptoes outside in pajamas and robe, a kindly conductor appears and cries, "All aboard!" The train has come to take the boy, as well as several other Santa-skeptical children, on a journey to the North Pole, where they will be allowed to discover the truth for themselves.

The conductor -- and the boy -- are both played by Tom Hanks (who plays six roles in all, including that of Santa) thanks to a cutting-edge computer technology called "performance capture." Instead of the cartoonish figures that populate standard computer-animated movies, the characters in "Polar Express" were rendered using live humans acting out the story while covered in dozens of tiny sensors that digitally captured their movements, which were then translated to film. The process also allows adults to play the children's characters.

The result is not perfect. There is something about the deadness of the characters' eyes -- they couldn't attach sensors to the actors' eyeballs -- that proves a bit disconcerting. Overall, though, it works: The characters have a timeless, storybook look (as opposed to a cartoonlike one), and they are infused with just enough human warmth to give the film a lifelike feeling.

It's the backdrop, though, that truly enchants. Not only do Van Allsburg's darkly magical illustrations come to glorious life in the film; so, too, do his familiar words. The train "thunders" just as he wrote it; as it journeys "over peaks and through valleys like a car on a roller coaster," viewers can't help but feel as if they are on a roller-coaster ride of their own, breathlessly zipping up mountains and dipping down huge ravines. The familiar lean wolves gracefully roam through Van Allsburg's cold, dark forests. And when the train ascends one final, towering mountain, it truly does seem that its riders are about to "scrape the moon."

Van Allsburg's tale, though, is a mere 29 pages, half of which consist solely of illustrations. Therein lies the problem: Zemeckis needed not only to add new characters and scenes (some successful, some less so, but we'll get to that in a minute), he also had to stretch out the fabled journey to the North Pole in order to fill a movie-length period of time. At some points, it feels like the filmmakers hijack the simple narrative and head off into Action Movie land, the better to make it last longer.

To extend the narrative, the boy (never named in the book, he's "Hero Boy" in the film credits) makes three friends on his journey. There is the bright-eyed, empathetic "Hero Girl," played by Nona Gaye; the nasal-voiced, overly talkative "Know-It-All" (Eddie Deezen); and the impoverished "Lonely Boy" (played by Hanks's former "Bosom Buddies" buddy Peter Scolari), who is picked up from a house on the proverbial "other side of the tracks." Hero Boy also has encounters with a mysterious hobo (again, played by Hanks), who lives on the snow-topped roof of the train.

The hobo is distracting, and his scenes add a few semi-scary moments (a desperate race atop the train, a menacing marionette) to a tale that, originally, managed to telegraph of sense of apprehension without any real sense of fear.

Not so for the expanded role of the other children on the train, who mostly bring more sweetness to Van Allsburg's simple tale. Lonely Boy, in particular, helps add some much-needed emotional resonance, albeit at the expense of overshadowing the classic ending to the book. As someone who has been perennially disappointed on Christmas, with his eventual joy he captures all the childlike wonder the holiday is meant to evoke. Remember what it felt like to believe? Alas, that flutter comes after a very, very long journey; the film, for all its beauty, plays far more to the eyes than the heart.

The Polar Express (93 minutes, at area theaters) is rated G.

The train, brought to cinematic life from Chris Van Allsburg's book, takes skeptical children, and viewers, on a roller-coaster ride of visual delights to find Santa Claus. Tom Hanks as The Conductor, one of six roles he plays using motion-capture technology.Santa, Hero Boy and the Conductor are just three of the six characters voiced by Tom Hanks in "The Polar Express."