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December 2014
Issue: June 1, 2010

COVER STORY: TWILIGHT ECLIPSE'S FURRY WOODLAND CREATURES

By: Ken McGorry
BERKELEY, CA — For New Moon, the second installment of the Twilight vampire series, director Chris Weitz tapped Phil Tippett’s studio to help introduce five menacing new characters —  wolfmen (and woman) who shape shift from humans to realistic wolves.
Tippett and company (www.tippett.com), including art director Nate Fredenburg, threw themselves into their lupine studies with characteristic intensity. The shop is well known for its early stop-motion work and its mastery of solid-body CG creatures such as the giant warrior insects seen in both Starship Trooper films.
But wolves are different. And they got different again for the latest Twilight film, Eclipse, directed by David Slade. For this third installment, Slade wanted more CG wolves (from five to eight), bigger wolves, and more physical interaction between the actors and the wolves. This includes everything from affectionate petting to fur pulling, fighting and biting, and a big wolf vs. vampire battle sequence.
Visual effects supervisor Eric Leven considers himself a long-term member of the Tippett VFX family — he spent two months on location in Canada with the company’s namesake and the Eclipse production crew. But he was new to CG wolves. Prior to delving onto the third movie the Tippett artists who worked on New Moon familiarized Leven (who shared VFX supervision with Matt Jacobs) with their CG wolf characters.
Slade also wanted a different look for his wolves. “We had to change some of the ‘groom style,’ the amount of fur, some of the colors of the wolves,” Leven says, “minimal changes but enough to make it interesting.”
In the beginning the production asked Leven and company to render more and more CG fur on the creatures. Fur is difficult and the Tippett staff needed to rethink their tools, workflow and memory management. However, “what they were really looking for was a different type of fur sheen,” Leven says. “You can have fur that looks soft or looks coarse and it doesn’t necessarily have to do with the amount of fur.” The Eclipse production team wanted their wolves’ coats to suggest a “softer, less clumpy feeling.” Ultimately Leven and company did increase the amount of fur significantly “but we also changed the style of the groom.”

INTERPOLATING FUR

To increase the volume and malleability of the fur, Tippett started with a set of “guide hairs” on a model’s surface which would serve to direct the action of the CG coat. Guide hairs determine the fur’s position on the model’s surface, and its “clumpiness” as well as many other characteristics. “We create them in two different ways to save memory.” Paint maps also describe the fur’s length, coarseness, width, color and more. Eclipse’s CG wolves sport a secondary layer of fur that, to save memory, does not follow the guide hairs; instead they are pure interpolation. “It was a new technique for us,” Leven says. “It allowed us to grow a lot more fur and get a really different look than we were able to get on the last show. RenderMan is optimized to grow millions of hairs, but you still have the limitations of the amount of memory you can deal with.”
The new fur system is more node-based than paint-map-based. “It actually works like a compositing package,” Leven says. “You can get a variety of looks really, really fast.” Tippett’s compositing supervisor was David Schnee.
The node-based system allowed the team to use “hardware preview” via the GPU, allowing them to review a shot and get feedback much faster, although without all the nuances of lighting and shading.
Leven says Eclipse features “a lot of long shots with eight wolves hanging out for six, seven, eight seconds at a time. It’s safe to say that if we had not come up with [the node-based] technique, we would not have been able to render the show.” In some sequences, like when they’re observing a foe, the wolves hold still. In such static shots the fur’s verisimilitude is of great importance because the audience can focus on it.
Tippett used Maya for animation, Shake for compositing, as well as Nuke, and its custom-built fur system was newly overhauled. CG supervisor on Eclipse was Aharon Bourland and CG character supervisor was Stephen Unterfranz. VFX producer was Ken Kokka.

INTERACTION

There are dramatic fight sequences in Eclipse and here again the Tippett interpolation technique helped the team add realism with virtual snow.
Tippett Studio had to come up with techniques to depict female lead Kirsten Stewart running her fingers through a wolf’s CG hair. “We had a particle-based technique where, if an actor’s hand is brushing through the fur, we could emit particles from the hand to the fur and those particles could drive different attributes [in the fur], like lay down, stand up or get more or less clumpy.”
Eclipse’s wolves are bigger — roughly six feet tall at the shoulder, yet they otherwise resemble regular timber wolves. For fight scenes actors would wrestle on camera with a big stuffed gray bag that stood in for an attacking wolf. (One rolling-and-tumbling fight sequence uses a digital double for the human character.)
The wolves in Eclipse, as per David Slade, are more animalistic and less empathetic than the wolves in the previous film. For both movies the Tippett animation crew studied the behavior and movements of real wolves and took hundreds of hours of video and thousands of photographs at a wolf preserve. “But from there we dealt with what the needs of the shot were.”
Animators would take their favorite movements by real wolves they studied and incorporate them as elements in the scripted movements of the CG moves. Animation supervisor was Tom Gibbons and lead animator was Randy D. Link. The Tippett crew numbered around 60 and they completed about 90 shots for Eclipse.
“There’s a great battle scene where all eight wolves are onscreen taking care of the evil vampires,” Leven says. “There’s some great interaction with Riley, one of the great evil vampires.”

HDRI

“We had some new techniques like our HDRI pipeline that we never used before. High dynamic range imaging is all the rage these days. You go out, take a bunch of pictures of sets including all the environment, the color of the sky, the ground and all the lights, you come back and [use that imaging] to get a perfectly lit CG creature.” That’s not the reality, Leven says, but “we were able to get much further much faster with the HDRI stuff.”
Solid objects are much easier to ray trace with than furry creatures which would require millions of calculations. The improvements brought by the HDRI pipeline made lighting easier. But, given the Twilight series’ vampire-friendly setting — the often rainy, cloudy environs around Seattle — natural lighting was flat and the DP, Javier Aguirresarobe, did not light specific areas of a frame in a woodland setting to accommodate CG wolves that were not there yet.
“Lighting became really important because the wolves really needed to fit the plate,” Leven says, adding that director Slade is a stickler for detail. Leven says lead lighter Marie-Laure Nguyen had to strike an exact balance to show off the Tippett wolves without allowing the shot to look artificial. In each shot the CG lighters had to blend just the right amount of fill light and the indirect lighting derived from HDRI in the film’s naturally low-contrast environments. 
The next big release for Tippett is Cats and Dogs 2. There will be plenty of fur flying in that CG-driven comedy but, Leven says, “The big deal was a hairless cat. That was an amazing set of challenges!”