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j u ly . a u g u s t 2 0 1 4 c g w 2 1 D I G I T A L C H A R A C T E R S evolutions from those built by the studio for Abraham Lincoln: Vampire Hunter. "We created the horses in partnership with Massey University's equine research department in Wellington," Win- quist says. "We did MRI scans for the musculature and lots of motion studies on treadmills. For this fi lm, we took that work to the next level with our latest muscle-based technology for creatures and our tissue solves. From a fur computation standpoint, horses were trickier than the apes. Maurice has 900,000 hairs. A horse has 3.2 million. And we ran fur simula- tions on their manes and tails. We worked with the shader de- partment to make sure we had BRDFs (bi-directional refl ec- tance distribution functions) that approximated body fur so we wouldn't have to render fur on horses far from camera." As for the animation, Bar- rett's team had to modify the motion of riders captured on horseback in saddles with stir- rups to create believable apes riding bareback. "The saddles and stirrups change the way the bodies move, so we had to iron that out," he says. "And as soon as they stood up, it was all over for us. We had to move the weight to the rear and have the apes grip with their feet and ankles." In addition to the hero apes, the animators had thousands of individual apes to control. "One of the TDs told me there were 20,000 individual apes," Barrett says. "Those were instances and we used Massive for big crowds. The motion-cap- ture team did a huge amount of crowd work. But when we had 100 or 200 apes, the directors wanted more specifi c motions – less Massive brains, more human brains. So we captured animators for those." C L U M P S O F F U R All the apes had fur that needed to be grown, groomed, and ren- dered, but the hero apes who performed in the rain presented particular problems. "We did wet fur for King Kong," Lemmon says. "But, we're at a whole diff erent level now. Making the fur look wet, matted, and mangy was important because so much happens in the rain. We had rebuilt our hair and fur system for The Hobbit, but for this fi lm, the grooming tools had to talk to simulation tools. They had to work together to drive the pooling of water and the clumping of fur. We hadn't put a water simulation through fur and onto the skin before." To help link hair dressing to simulation, researchers grew Wig, a new dynamic rod-based system, from the studio's Barbershop. "When fur gets wet and starts to clump, it goes through diff erent phases," Lemmon ex- plains. "The water beads on top in some cases, and in others, it wicks down and gets sucked into the clump. We had to be able to model wet fur and set it in diff erent types of clumps. Then, we could pre-saturate areas with water based on that clumping and drive additional water though it in that state. Drips enter the simulation, causing pools to get larger. They break free and fall on skin and other bits of fur. We tried to be effi cient by simulating only the part of the ape visible to cam- era, but it was still gigabytes of data being pushed around." As this happens, shaders send light into the fur and cause dual scattering. "We had to be very smart about shading the wet fur," Winquist says. "It was Apes in Stereo "Matt [Reeves, director] was ambivalent about shooting the fi lm in native stereo," says Erik Winquist, VFX supervisor at Weta Digital. "He liked an anamor- phic, '70s/'80s look. But, the studio wanted it to be in 3D. By the end of produc- tion, though, Matt was very excited about the 3D aspect and thrilled by the extra dimension it brought into the fi lm. And that was great. So much of the scenes takes place in the rain, in the woods, with fi ddly plants and ferns, it would have been a worst-case scenario for a post-conversion house. I can't imagine how painful it would have been to post-convert practical rain in the foreground. And we would have had to work with them on that." Having native stereo didn't mean there was no pain, however, especially for the shots created with live-action horses and CG apes. "It was a huge matchmove challenge," says Dan Barrett, animation supervisor. "The artists had to paint out the rider and put the ape on the horse. It had to register correctly in screen space and not dri when someone put on the 3D glasses." – Barbara Robertson A GOOD DEAL OF THE FEATURE FILM TAKES PLACE IN WET WEATHER, SO COMPUTER GRAPHICS SCIENTISTS AT WETA DIGITAL REBUILT THE HAIR AND FUR SYSTEM TO WORK WELL WITH WATER - SIMULATION TOOLS.