By now, you no doubt have an opinion of THE TWILIGHT SAGA, the inescapable movie adaptations of Stephenie Meyer’s novels. The latest entry, ECLIPSE, has been declared the best in the series, likely due to the more straightforward conflict and clearer stakes of its plot. While ECLIPSE is unlikely to convert non-fans, the FX are inarguably better than in the previous entries, especially the computer-generated wolves created by Tippett Studio.

When introduced in NEW MOON, these canines stayed on the leash outside of a few scuffles and bared fangs. ECLIPSE features a wilder wolf pack whose increased feral tendencies emphasize the differences between Bella’s suitors—and did we mention that the movie climaxes with snarling werewolves savagely attacking bloodthirsty newborn vampires?

The company responsible for the CG lycanthropes is Tippett Studio, founded by FX pioneer Phil Tippett, famous for stop-motion classics like the AT-AT walkers in THE EMPIRE STRIKES BACK and the lumbering ED-209 in ROBOCOP. In the CGI age, Tippett Studio has created everything from the giant bugs in Paul Verhoeven’s STARSHIP TROOPERS to the talking pets in this summer’s CATS AND DOGS: THE REVENGE OF KITTY GALORE. For ECLIPSE, Eric Leven served as the company’s visual FX supervisor, bringing the wolves to ferocious life.

Unlike some cinematic wolfmen, TWILIGHT’s pack are quadrupeds very similar to real wolves, albeit enormous by comparison. After arriving late to NEW MOON’s FX, Leven observed director Chris Weitz putting an emphasis on anthropomorphizing the otherwise physically accurate animals. “Chris wanted the audience to understand everything the wolves were feeling,” Leven notes.

Before NEW MOON, the Tippett Studio team logged time at a nature preserve in Los Angeles, observing real, fully grown wolves first-hand. That homework proved handy when ECLIPSE director David Slade requested a more menacing brood. “The work on NEW MOON dovetailed into ECLIPSE, and David came in and made it clear we were going to get away from humanizing the wolves,” Leven recalls. “We were going to make them animals again.” Such choices were informed by ECLIPSE’s story (scripted by Melissa Rosenberg), in which the tension between lycanthropes and vampires is more overt and expanded from NEW MOON. “In the second movie, they were played more like sentries,” Leven notes. “In this one, they’re wilder. You don’t know whether they’re going to jump on you or not.” Despite that, the creatures of ECLIPSE are capable of acting nuances; witness the moment in which the alpha wolf watches the Cullen vampire clan sparring with each other. While the wolf attempts to keep his threatening posture, his body language will be familiar to anybody who has ordered their dog to sit out on a fun activity.

The freedom to add character touches like this led to Leven’s personal favorite effect in ECLIPSE, when Bella (Kristen Stewart) runs her hand over Jacob-wolf in full view of Edward (Robert Pattinson). It’s a challenging effect, requiring Stewart to physically interact with the CG animal, as well as an emotionally loaded story moment, as Edward observes the connection between Bella and Jacob for himself. The end result is as striking a visual as the series has to offer, with uncanny texture on the digital fur. “That was another mandate from the director,” Leven says. “He saw the first pass and said, ‘I need more fur!’ Fur is notoriously difficult in CGI. We added to the total number of hairs, and it turned out that wasn’t the issue. It was really the style of the fur, the sheen of the fur, what happened when the light hit it.

“Sometimes it’s difficult for a director to communicate what they want,” Leven points out, “because they’re not speaking in the kinds of technical terms we use. The effects team has to establish a language with every new filmmaker. It can be pretty rough at first.”

Those differences at the helm are the most obvious within an otherwise cohesive series. “We worked with much of the same production crew as NEW MOON, but every movie with a new director is like a fresh relationship,” Leven says. “Each one wants to put his or her personal stamp on the material. David Slade has an action-oriented style and specific ideas about what he wants to see. We always want to be pushed to do our best work. Everybody here is the kind of person who wants to see vampires and werewolves tearing into each other.” Distinctions in directing style contributed specifically to Tippett Studio’s workload, which included practical stand-ins for the hairy beasts. “Chris Weitz had nothing there to represent the wolves, just a tennis ball for the eyeline,” Leven reveals. “David introduced these giant grey beanbags to put into the shots and give the actors a sense of size and weight for them.”

Despite the TWILIGHT series’ high profile, Leven is quick to point out that ECLIPSE is “still a relatively low-budget film.” According to the artist, that didn’t inhibit the quality of the FX so much as tighten the schedule, since “we didn’t get a lot of time for retakes. On a big-budget movie, they’ll tweak everything right up until the very end.” ECLIPSE is saturated with special FX, from the Cullens’ amber eyes to the much-improved-upon, relatively subtle sparkling of Edward’s skin in the sunlight. Missing such details would raise the ire of TWILIGHT’s fan base, but Leven is quick to point out that their praise is often earned the simple way: by going back to the source. “Some fans will thank us for a scene or a moment, saying, ‘That looked just like the way I imagined it from the book!’ Well, that’s because we’re using the book,” Leven says with a chuckle. “In one instance we had a new character, Quil, and we were trying to decide what color to make his fur. Ultimately, all we had to do was open the book and read what color his fur was.”

Perceptive viewers will find something familiar in the low brow and dark irises of Jacob-wolf’s eyes. “Those are based on [actor] Taylor [Lautner]’s eyes,” says Leven. “We had given the wolves human eyes in NEW MOON, to help convey their emotions. With the idea of making the wolves more animalistic in ECLIPSE, we thought about how distinctive a real wolf’s eyes are. So the wolves in ECLIPSE all had yellow wolf eyes at first, and David Slade loved it—everybody loved it. They stayed that way until very close to the end, when Stephenie Meyer came in and said, ‘Are the yellow eyes on the wolves too similar to the vampires’ eyes?’ So we went back to human eyes on the wolves.”

Regarding the ambivalent attitude of many horror fans to the TWILIGHT series, Leven refers to the potential influence of ECLIPSE’s opening-weekend gross. “Hollywood pays attention to numbers,” he says. “The second sequel to a movie about vampires and werewolves made over $150 million in five days. The success of the TWILIGHT series means we’re going to get a lot more monsters in movies.”