Patchi (voiced by Justin Long), left, is much smaller than his brother, Scowler (Skyler Stone), in “ Walking With Dinosaurs 3D.” ( 20th Century Fox)

Like an elaborately decorated wedding cake, the kid-friendly “ Walking With Dinosaurs 3D” may leave you wondering how something so stunning could end up being so bland. Aesthetic attention to detail, even when it’s painstaking, goes only so far when the content is mediocre.

The movie begins with a fleeting, modern-day framing device about an archaeologist (Karl Urban) on a dig with his niece and nephew, and then goes back to prehistoric times to follow a young pachyrhinosaurus, Patchi (voiced by Justin Long), and his best friend and co-narrator, a colorful bird named Alex (John Leguizamo).

Patchi is the runt among his siblings, and a run-in with a larger dino leaves him with a distinctive hole in the frill projecting above his head. And, yet, this underdog has plenty of spirit and more smarts than his burlier brethren.
The movie aims to show the harshness of the dinosaur-eat- dinosaur world and it doesn’t shy from killing off parental figures, Disney style. Yet a bit of comedy and a little love (Patchi falls for Juniper, a pachyrhinosaurus from another herd) softens the reality. Nevertheless, the plot feels haphazard and repetitive, with frequent scenes depicting the dangers as the herd travels north and south depending on the season. And curiously, as new characters appear, the action pauses while a child’s voice states the type of dinosaur, the meaning of its name and whether it’s a carnivore, omnivore or herbivore. This might help the audience understand whether that creature will be a danger to Patchi, but the information could have been conveyed within the plot.

Such is one of the problems with the ad­ven­ture, which is based on a documentary television series of the same name (minus the 3-D).

“ Walking With Dinosaurs 3D” seems to have an identity crisis. Does it want to be edutainment or a feature film? Its reported $85 million budget lands it closer to a blockbuster than to “The Voyage of the Mimi,” but it doesn’t feel adequate in either category.

An interview with Barry Cook, who directed the movie with Neil Nightingale, sheds some light on the varied tones. At first, “ Walking With Dinosaurs” wasn’t going to have dialogue; viewers could figure out the story for themselves. The voices were added later, and it’s obvious. The characters who speak English, which is a small group, appear to be communicating telepathically, talking to each other without moving their mouths. It’s oddly distracting, and, with one very funny exception, the banter doesn’t go much beyond scatological humor and banal exchanges.
It’s interesting to consider what the movie would have been like without the voices. The images are impressive and intense. The movie’s scenery was shot in New Zealand and Alaska, and the backdrops make an ideal canvas for the computer-generated creatures. The migrating herds look amazingly naturalistic.

Of course, the vocals help keep the little ones interested and open up the movie’s potential appeal beyond museum screens. It just seems that any film with so much talent poured into its visuals could have assembled an equally worthy script.