rated R

Is it possible for a vampire movie to fly too close to the sun? “Daybreakers” does just that—it’s a stylish, ambitious melding of sci-fi and horror. When it succeeds, it does so gracefully, but when it stumbles, it nearly collapses.

“Daybreakers” promises so much: visceral vampire action, clever world building, and a thoughtful tweak on the vampire mythos, all wrapped in an allegory about dwindling natural resources. Brothers Peter and Michael Spierig, who wrote and directed “Daybreakers,” deliver on a handful of these promises and make half-hearted attempts at the rest. It’s not a complete failure, but it’s more than a bit disappointing.

In the world of “Daybreakers,” it is 2019, and 10 years earlier, a plague turned most humans into vampires. Some turned willingly, lured by the promise of immortality. Others turned because they had no choice, and a handful became vampires against their will. Among that last group is Edward Dalton (Ethan Hawke), a hematologist working on creating a synthetic blood substitute. After a decade of farming blood from humans (and hunting down the few remaining human survivors), the blood supply is running out—think of it as Peak Blood. Dalton is under pressure from his boss, Charles Bromley (Sam Neill), who controls the largest blood supply in America, to produce results. But Dalton, self-loathing vampire that he is, wants to find a cure for vampirism instead. Enter Elvis (Willem Dafoe), a former vampire who accidentally cured himself after crashing his badass muscle car on a sunny afternoon. Elvis and a band of human survivors ask Dalton to help them produce a cure. Meanwhile, vampire society deteriorates under the specter of total starvation.

The plague not only turned everyone into a vampire but made everyone super stylish, as well. “Daybreakers” has a great future-noir look to it—sharp-dressed vampires zip around in electric cars and sip from cups of coffee mixed with blood. The subways have been augmented with “subwalks,” underground tunnels where vampires can walk safely during daylight hours. Most cars are equipped with a daytime driving mode, with sun-shields over the windows and cameras mounted on top of the vehicle. Vampires deprived of blood devolve into snarling, bat-like creatures. The Spierigs’ careful attention to detail throughout most the film results in some first-rate world building. The vampire society is fleshed out and real, and that helps sell the film’s ambitious premise.

If only the characters were so detailed. The Spierigs’ previous film, 2003’s “Undead,” was a low-budget zombie/sci-fi comedy anchored by its cast of charming, kooky survivors.  But in “Daybreakers,” Dalton and Elvis are little more than bare sketches. This isn’t so bad for an actor like Dafoe—he hams it up nicely as a redneck gear head who likes to quote the King. But Hawke seems adrift. His character isn’t as cool as Dafoe’s or as evil as Neill’s capitalist bloodsucker. Hawke’s motivations are weak and his moral conflicts are vague. As a hero, he’s difficult to care about. Without strong characters, all the fantastic efforts at world building are for naught—a strong foundation means nothing when it’s topped with flimsy characters.

The climax of “Daybreakers” proves to be just as disposable. The cure sought by Hawke and Dafoe is goofy and nonsensical, and the massive blood riots and vampire mutations promised at the outset amount to a fracas at a coffee stand and the roundup of maybe a dozen devolved vamps. The stakes feel high at the outset of “Daybreakers,” but by the end, the decline and fall of vampire civilization isn’t worth more than a shrug.

There’s one area where the Spierigs follow through, and that’s in the visual effects department. The brothers teamed with Peter Jackson’s Weta Workshop for the effects, and “Daybreakers” boasts a seamless blend of computer-generated and practical effects. The devolved vampires (dubbed “subsiders” by the vampire media) especially look great, and it’s a testament to the limits of CGI when it comes to monster making (“Avatar” notwithstanding). As the vampires grow more ravenous, limbs fly and blood spurts all over the screen, and the Spierigs mostly deliver on their promise of monster mayhem.

Unfortunately, “Daybreakers” is a victim of its own high expectations. Because it excels in so many places, its failings are all the more glaring and disappointing. Even then, “Daybreakers” is still entertaining, and a welcome departure from the bloodless vampires of “Twilight” and its ilk. “Daybreakers” burns out on its own premise instead of fading away gracefully. Vampire civilization may be doomed, but “Daybreakers” promises that, flaws and all, vampire flicks still have some life in them.