Jay Davis was the lead animator on the signature "Golden Army" sequence in Hellboy II, which contains complex animation and stunning visuals. All images © Universal.

Writer/director Guillermo del Toro is known for imagining eye-catching characters in Hellboy and Pan's Labyrinth, and he lives up to that reputation with his regiments of battling robots in Universal Pictures' Hellboy II: The Golden Army. Jay Davis was the lead animator on the signature "Golden Army" sequence that features those robots, moving from L.A. to London for a year to work at Double Negative on this film.

"The Golden Army sequence is chock full of complex animation and some pretty stunning visual craziness," says Davis. "I don't want to spoil anything," he adds, choosing his words carefully so as not to reveal plot points. "These robots are 12-feet-tall and made out of metal and have mandibles like an insect but no facial features, so all the character work had to be pantomime. They also had glowing cogs inside -- small bits of nanotechnology -- that were their inner workings. They were hard characters to animate because of that."

While the robot army includes thousands of individuals, Davis notes that low-res behaviors for the epic 'cast of thousands' were animated on cards. The primary focus for his computer animation team was on the roughly 30 hero robots that interact with Hellboy (Ron Perlman). Fortunately, Davis was brought onto the project early enough by DNeg Animation Supervisor Eamonn Butler so that he could witness the shooting of the Golden Army sequence plate photography in Budapest. (Davis, who spent 12 years as a Disney animator on such films as Meet the Robinsons and Hunchback of Notre Dame, had previously worked with Butler on Disney's Dinosaur.)

Davis was happy to have watched del Toro on set directing the action in which DNeg's CG robots would be integrated. "On set we had cardboard cutouts so the actors could see how big these robots were. There were no animatronics, so it was really important to have those cutouts on set. Some of the shots were over-the-shoulder of a robot looking down at Hellboy, or Hellboy looking up at a robot. We had to get the eyelines correct."

"There were also guys in green suits and scaffolding for the stunt guys to jump onto," Davis continues. "Hellboy jumps from robot to robot and smashes them or shoots them in the head. It was tricky because the scaffolding was static. We had to animate the robots so they didn't look static, so that Hellboy looked like he was standing on them. There's a scene where Hellboy lifts up the chin of a robot and shoots down its neck. On set there was a practical prop, roughly the size and shape of the head, painted green. Hellboy lifts it up and shoots down it, so the matchmoving had to be really tight."

But the challenge of integrating robots into plate photography only accounted for about half of DNeg's animation assignment. "There are some really long all-CG shots," says Davis. "The shots with plates were actually easier." To choreograph their shots, DNeg animators did three rounds of Maya 3D previs that included digital doubles of the main actors in the sequence, as well as the robots. "While Guillermo was shooting in Budapest, Eamonn was working with the animators doing previs. Guillermo shot the film in sequence, which was a slow way to do it, but that insured that the continuity worked. He had in his head what he wanted to do, and he did it. He also ended up using a lot of the previs stuff that we had done."