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in-depth features about how cutting-edge CG was created for various movies
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Artists Model and Groom Realisitic CG Wolves for the Thriller New Moon
Just as the Twilight book-turned-movie series has painted a romantic picture of vampires, it is now similarly redefining our notion of werewolves. For The Twilight Saga: New Moon, the second film based on the book from Stephenie Meyer, the audience is introduced to this additional group of supernatural characters. Yet, these are not the scary, bloodthirsty beasts from folklore; in the book, they are handsome young men of Native American decent who can morph into majestic large wolves. But it is CG magic performed at Tippett Studio that enables this transformation to take place on screen with the degree of realism needed to sell the scenes.
In the movie New Moon, actors shape-shift into realistic, albeit much larger than normal, CG
wolves. Tippett Studio performed the transformation, which occurs quickly, in a
matter of just a few frames.
According to Matt Jacobs, co-visual effects supervisor at Tippett, the group was asked to conjure up some initial designs for the beasts without knowing where on the wolf-to-monster dial the New Moon creatures would land. Director Chris Weitz later determined that they would fall more on the side of real wolves, with realistic proportions but much larger than a typical wolf. “His objective was to stay true to what the fans of the Twilight series expected after reading the books and what the author intended when she wrote the books, and that was not some man/wolf creature,” says Jacobs.
The Tippett team created five realistic CG wolves, each with a distinct look and representing one of five Native American youths in the film—including the main character Jacob—who shape-shift into the animals. In the movie, Jacob (Taylor Lautner) befriends and falls in love with Bella (Kristen Stewart), who still harbors deep feelings for the vampire Edward after he and his family move away when the desire for Bella’s blood became too great. At first, Bella sees Jacob only as a friend, but eventually grows to love him, too. But, just as Edward has a dark supernatural side, so, too, does Jacob. He is a werewolf, which forever has been the mortal enemy of vampires. Jacob and his pack proceed to patrol the forests to guard against a new vampire threat that leaves Bella more vulnerable than ever without Edward and his family to protect her.
To support the story line, the CG artists had to model and animate the digital animals for approximately 60 shots, making sure that their size—akin to small horses—comes through on screen, particularly when there is little object reference in the shots to
illustrate how large these animals are. “We tried to do little things with effects to help sell the mass of these characters in the animation performance, and spent a lot of time working on the effects,” says art director Nate Fredenburg, “the weight of the fur, the jiggle of muscle.”
However, the most complicated aspect was the fur. A real wolf’s fur has a lot of color variation along the length of the hair. Also, the type and thickness of the fur varies over a wolf’s body. “Tackling the multiple looks in one creature and making the fur blend together was definitely one of the more challenging aspects of the animals,” says Jacobs.
Animal Research
To get a handle on how wolves actually look, move, and react, leads from modeling, animation, painting, lighting, and so forth took a field trip to Wolf Mountain Sanctuary in California, where the team was able to observe, interact with, film, and document the animals. “I was surprised at just how big a real wolf is,” says Jacobs, who estimates the real animals at about 170 pounds.
Jacobs notes that the group learned a good deal about the wolves’ motions, what their fur looks like, and some of their subtle mannerisms, all of which the animators tried to incorporate into the performances of the digital animals. “The wolves we created weren’t supposed to be wild,” he explains. “They had to perform and do things maybe wild wolves wouldn’t do at times, but we still tried to draw on what we had learned and observed, to bring more realism to their performances.”
According to Tom Gibbons, animation zzzsupervisor, one of the big tasks for him and his team was to create wolves that represented the natural world but also had a touch of the human character as portrayed by the actor in that role. “The Jacob wolf would have a bit of the Jacob personality, the Paul wolf would have a bit of Paul, and the Sam wolf would reflect some of that character,” he says. “Where to finesse those lines was a big challenge for us. Those three characters were the most personality-driven in this story. We looked at the actors’ performances and sussed out how to put that into a naturalistic wolf and not break the illusion that it was a real wolf.”
Preparing the Pack
The modelers, lead by Jack Kim, used orthographic images collected from the field trip and from books and other sources as model references. They also purchased a taxidermy “blank” to obtain accurate information about the animal’s underlying structure beneath the thick coat—a reference that proved especially beneficial, says Jacobs.
Using Autodesk’s Maya, the artists built the surface model for the wolf, focusing on creating it to the accurate scale and proportion of a real wolf, and used Autodesk’s Mudbox for displacement sculpting. They then slightly altered the model for each subsequent wolf, such as the length of the snout and ears.
Next, Kim populated the model with approximately 4000 splines to achieve the overall shape and base length of the fur.
Afterward, the model was sent to the paint department, where the fur was styled and groomed using Tippett’s new in-house fur tool, Furator, which interpolates all the hairs on the character using the shape of nearby curves to influence the look of the in-between curves. With Furator’s node graph, the artist assigned to the project added secondary and tertiary details to the fur in terms of the length, scale, rotation, elevation, scraggle, clumping?…?all the features that give it “character.” (An accompanying story about the creation and capabilities of Furator can be found on www.cgw.com, under Web Exclusives.)
Key to generating the realistic fur was achieving various qualities and looks across the
animals’ bodies for instance, short hair on the muzzles and big, bushy fur on the tails. Also,
the painters had to incorporate color ticking down the length of each hair on all the wolves,
a process achieved using RenderMan shaders written in-house.
As Fredenburg explains, the painter had to give the fur different qualities literally from the nose to the tail. “We had to come up with a plan to integrate all the different types of hair and be able to deal with different look issues on various parts of the body,” he says. For instance, the muzzle was fairly straightforward, with short hair that the artists then mussed up so it would not be computer perfect. On the belly, the fur was clumped and long; on the back, medium length. On the tail, the fur was big and bushy; on the feet, short and velvety.
The biggest challenge was at the neck, where the velvety, short fur on the muzzle quickly becomes long and mane-like on the cheeks and the chops, those pointy tufts of fur that extend from the cheeks and give them their iconic wolf look. “We spent a lot of time, probably more than we wanted to, getting the shape,” says Fredenburg.
Achieving that recognizable attribute required a great deal of back and forth between paint and modeling, whereby the modelers would reshape the splines to refine the look, and the painter would break up the splines with clumping and scraggle. “The painter would rotate the hairs, elevate them, and clump them together on these animals, which have very dense fur coats that tend to get matted,” says Fredenburg.
Built by Mike Farnsworth and Andrew Gardner and used first for Cats & Dogs 2 (still in production), Furator enables artists to put together large sets of operations—for instance, loading the geometry and fur, interpolating the fur, applying a length modification, scraggle, and clump, merging fur, splitting fur—and store it as a project that, at runtime, generates the final look of the coat. The project exports as caches with huge amounts of fur in them; the caches are then rendered in Pixar’s RenderMan, though the tool is renderer agnostic.
Two other painters incorporated the color variations on each hair. This variation had to be carried out on all five of the wolves: Jacob, which was rust brown; Sam, black; Paul, gray; Jared, chocolate brown; and Embry, lighter gray.
“They had to work collaboratively. One complicated thing about wolves is they have very unique color ticking down the length of the hair that contributes to its patterning,” says Fredenburg. “We just couldn’t paint the regions of color; we had to build up the patterning by working the color down the length of each individual hair.”
RenderMan shaders created in-house enabled the painters to apply color to the root, the midsection, and tip of the hair. A map lets them control where the blend occurs between those areas. “The painters would basically paint three versions of the coloration of the wolf and blend them down the hair with these mix maps,” explains Fredenburg.
Tippett employed its new Furator grooming software to generate the fur on the digital animals.
Each wolf model contains approximately four million hairs.
To help sell the animals into the shots, the team used a function in Furator that runs a 3D noise field through the fur, making it appear as if a soft breeze was blowing through the animals’ hair. Dialing it up resulted in the fur getting blown about, as it does in one scene that was shot on a very windy day. “The animal felt a little dead without any fur motion,” says Jacobs.
Ahron Bourland, technical art director, wrote a shader for the fur that enabled it to stand up in two full-frame, close-up shots of the Jacob wolf’s eyes, in which Bella’s reflection can be seen. As for the eye itself, rather than model a physically accurate eye with minutia detail, the group focused the shot on the character reflection. “We did a bunch of focal depth blurring that helped us not get caught up and render detail that was unnecessary,” says Fredenburg. “It was not about seeing the veins in the corner of the eyes or the mucus looking just right. It was about the emotional moment of seeing Bella’s reflection.”
A texture reference from the actor was used for the wolf’s eyes, to support the book’s description of the wolves: that they had uncharacteristically human-like eyes.
In all, each wolf contains approximately four million hairs—more than Tippett has grown on any previous character. The studio has the technology in place to render more than 12 million, should the situation arise, contends Gardner. Furthermore, R&D is experimenting with a system for instancing geometry based on curves, which would be useful for objects such as feathers.
In Motion
Tippett, in fact, has crafted a number of CG animals for a number of films, from a rat (Charlotte’s Web), to a chipmunk (Enchanted), to goblins and trolls (The Spiderwick Chronicles). The studio even did wolves for The Golden Compass, but the big difference here was these wolves were main characters that had to act and perform.
Under the direction of Gibbons, the crew built the animation rig for the general wolf model, Jacob, within Maya, then propagated it out to the other characters. A number of plug-ins from the rigging department helped the animators achieve specific performances for the animals.
Unlike many furred characters of late, these wolves have no dialog, nor do they emote a wide range of expressions. “We couldn’t take the wolf out of wolf land. We had to walk a thin line in how far we could take the emotional moments,” says Gibbons. To this end, the group developed a detailed facial rig that focused on the animal’s snarl.
“We kind of loaded up controls in the snarl that we normally distribute through the face rig,” says Fredenburg. “I am not sure how many shapes we had, probably several hundred. We spent most of the time constructing the nose and muzzle. Wolves have this crazy ability when they snarl; it looks like they are peeling the skin off their face. It’s kind of creepy. We built that in and worked with the director to find the appropriate level for the characters because they couldn’t be too creepy or scary.”
In addition, the animators used a number of blendshapes, and on top of those, built a cluster rig whereby they could accentuate the blendshape results in order to get certain expressions. “We were going for something naturalistically real, so we didn’t exaggerate shapes like you would see in a more cartoonish character,” Gibbons says.
In the film, the animals are shown running, jumping, breathing heavily, and so forth. “The moments when the wolves are standing, breathing, those were the controls with which we worked the most on the rigging and animation sides, so that those particular moments would carry over realistically,” says Gibbons. “We couldn’t break the illusion of believability for the audience.”
The wolves were composited into the scenes using Apple’s Shake.
Despite all the experience the group has had with furry animals, even wolves, these animals presented a challenge unlike any other, contends Jacobs.
The key to the project’s success, notes Fredenburg, was keeping an eye on the final picture. “That is something Phil [Tippett] drums into our heads,” he says. “We were not trying to write a SIGGRAPH paper with this. We were looking at the final image and staying focused on the things we needed to address in order to get the final image looking just right. We could have easily have gotten into a large science experiment with the complexity of this fur, but we boiled it down to the essential elements and did a good job focusing on them.”
And that helped make this project a howling success.