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November 2016

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TROLLS 34 POST NOVEMBER 2016 has pale pink hair, rosy cheeks and a disarming, charming overbite. "Craig Kellman designed the Bergens," Cronkhite says. "We refer- enced the late '60s and early '70s, when the troll dolls were popular. The trolls are like the hippies of the '70s, and the Bergens are more the subur- banites. They're kind of the monsters in our movie. We don't like them. They represent the worst of the '70s — polyester, plastic. They litter and pollute. Their food is monochromatic fast food." The Bergens have leathery skin, greasy hair and they drool. Each Bergen had its own design and model. "We tried to match different bodies with different heads, but the neck was a problem because of the design differences," says visual effects supervisor Philippe Denis. "However, even though the characters were so different, when we put them together to make a crowd, they really felt like they were in the same world because of the design language." For the fuzzy trolls, which look more similar from one to another, modelers worked with generic male and female models, plus what the crew calls a "snack pack" of heroes, which were Poppy's friends. "When I looked at Kendal's concept art, I got very excited because the visuals were so different from anything we had done before, but right away I saw lots of hair — huge hair — the fuzz, the clothing, the texture on the ground," Denis recalls. HAIR-RAISING EFFECTS For the most part, a troll's hair stays upright, but it can stretch a great distance and bend into unusual and useful shapes. It's more like wool than human hair; silky, but diffuse rather than shiny. The trolls can use their hair as a tool or even a weapon. The effects crew spent nearly a month of trial and error before they were satisfied with the way the hair reacted as the trolls moved through shots. They started with Poppy's hair in her candlewick design. "It was important to get the simula- tion right," Denis says. "At first the hair was either too stiff or moving too much and distracting. So we stopped trying to work with the stylized hair and began running simulations on ge- neric hair to get the feel of what troll hair can do. It needed to spread when shaken, but not too wide. There had to be a lightness to the feel, lighter than if it were string." When the hair becomes a ribbon, it's driven by animation rather than simulation. "Animators could stretch and place guide curves," Denis says. "Then the character effects team de- fined the motion and overall shape of the hair. The guide hairs are driven by character effects, and the in-between hairs are driven by geometry." When the trolls, and for that mat- ter, the Bergens, move, the simulation engine moved their clothes with them. "We had to scale the clothes for the little guys, so they're pretty rigid because of the thickness of the felt," Denis says. "The Bergens are more human-sized." To give the trolls — and the envi- ronment around them — the fuzzy, felted, fabric-art texture designed by the artists, the effects team used displacement and fur. "The trolls are like gummy bears with fur," Denis says. "It was a chal- lenge. When we started production, we created a beautiful image. Then, we had to make sure the detail could render for the length of the film. There is lots of fuzziness in the film — the trolls, the other creatures, the world around them." Level of detail helped manage the rendering requirements. DreamWorks uses a proprietary scan-line render- er. "When the trolls are away from camera and small, we use displace- ment," Denis says. "When they're close enough to see the fuzz, we use a fur shader." The crew handled elements in the environment similarly. Trees, for example, might be geometry with fur shaders or displacement. "When the camera pulls back, the texture becomes just displacement," Denis explains. "But the shader had to respond to the light, so the trees still seemed like felt, not plastic. Every time I did surfacing rounds, I knew we were in good shape when I wanted to touch the fuzzy thing. It became a checkpoint." SETTING THE TONE The biggest challenge for the effects crew, though, was the number of sets. There's the troll village, Bergen town and many environments in between. "The challenge and the fun was that our effects needed to fit into this kind of handmade world. Almost like a stop-motion world," Denis says. "Our grass was felt. Our fire looks like hair. Our hair looks like fire. For dust, we use a little piece of fuzz. And we made the tree roots from a sheet of gauze-like fabric. It isn't stop-motion. There's blur. But there is a little feel of that." Throughout the film, the crew used shallow depth of field, matte paintings Bergens each have their own unique design. Hair is driven through animation rather than simulation.

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