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Visual Effects n n n n In addition to Aang’s animals, the animators had to move the huge creatures that the Fire Nation warriors ride into battle. Te creatures look hybrid between a rhinoceros and a Komo- do dragon. “Te thing about Komodo dragons is that they have a goofy way of walking,” Har- rington says. “Tey lead with their elbows and drag their knuckles. It looked odd when we put that movement on a giant creature, so we made the creature move more like a bulldog.” In one shot, the creature scales an ice wall, digging into the wall with its claws, moving purposefully and steadily given the size of the beast. “You have to show the effort it takes for something that heavy to climb a wall,” Har- rington says. “If you rush it, it looks fake.” Skin and muscle simulation applied after ani- mation helped add believability, as well. Te fourth creature, a spirit dragon, is the least visible and the most complicated. “Night’s concept was to have an abstract coil of snake in a cave, and each time you see him, we reveal a little more,” Harrington says. “You see a close- up of his eye and notice a third eyelid. Ten, the next time, you see his whole face. Finally, at the end, he leaves the cave and you get a glimpse of how giant and majestic he is. He opens his wings, and he’s amazing and beauti- ful. But, as soon as you take in his beauty and majesty, we obscure him in smoke, and you don’t see him anymore. He is a complicated creature utilized effectively.” Digital Double Although Noah Ringer, the young actor who plays Aang, is a skilled martial artist, many of the shots were too dangerous for the child actor. One shot in which he’s fighting several warriors all at once, for example, continues for 5000 frames. “We knew we would do some flying and gliding shots that the stuntperson couldn’t do, but as the show progressed, we took on more challenging digital-double stunt work,” Harrington says. Ringer’s stunt double was a woman about his size, so ILM replaced her head in the footage with Ringer’s head. “We decided to do something a little dif- ferent this time,” Helman says. “Before, we’d capture the actor in a rest pose and then build a library of shapes based on photographs. But what happens is that when you transition to shapes, it doesn’t always look like the actor again because we all have a specific way to go from smiling to not smiling, for example. So we decided to capture the in-betweens.” To do that, they had Ringer sit in the middle of a stage surrounded by six monitors. Te shot with the stunt double played on those monitors so he could mimic the action as he watched and moved around. While he acted, ILM captured his face—textures and performance—with six HD cameras plus one positioned in front of his face. Te studio’s “clone cam” technique helped the team build a CG model from the footage and texture it. Tey also used the captured foot- age to move the model. “Tim [Harrington] could look at the captured performances and pick the ones he wanted for the shot, and then we decoded the information,” Helman explains. “So instead of being driven by keyframe shapes, the actor drove the perfor- mance of the CG face.” Animators could edit the performance in much the same way they’d edit motion-capture data applied to a facial rig. “Ten, on top of that, we did a final tech- nique to have a one-to-one match,” Har- rington says. “Te R&D department came up with a process called the Mardi solver.” While Ringer performed, he wore a tracking device that helped the team stabilize his head and iso- late his facial performance. Ten, using Mardi, rather than placing an elaborate temple in a viewer’s face for other shots, they hid much of it behind trees in a park. “Te environments are difficult work be- cause the project is geared toward getting things to look real,” Helman says. “So, my push was that if we’re doing geography, we should shoot something, even if we’re going to replace it. Tat way, the camera move would be correct, the physical timing would be cor- rect. And that’s something Night appreciates.” And that gave the digital matte painters a starting point for many shots. Ten, they pored through Flickr images looking for vacation photos that showed environments with an Asian influence. “It was all about capturing the vibe of a real place,” says digital matte painter Barry Williams. “With CG, it’s easy to get off track. I needed to know how it would look if I shot something with this environment at this time of day. Night wanted fantasy with a realistic edge.” Behind Aang is a computer-generated environment, one of many created for the film by ILM’s digital matte-painting department. they snapped that geometry with the animated character. “Te gross movement has to come from the stuntwoman, so we needed to apply Ringer’s performance to a non-moving head and then put that head into the plate,” Har- rington says. “Te cool thing about the digi- tal-double work is that we had a small enough number of shots that we could try out this in- novative new technique.” Building a (Non-magical) World To create a world in which element bending might take place, ILM’s digital matte-painting department built air temples for the Fire Na- tion, carved buildings out of huge ice cliffs for the Northern Water Tribe, and created other digital locations. When the painters built air temples for the Fire Nation, they added in- dustrial-looking bridges to reach them. And, And, for that style, the director picked the perfect visual effects supervisor. “I think that’s what I like doing best, effects that are part of the story,” Helman says. “I think this film is fresh in that the effects are not the star. In other movies, you have effects with explosions and incredible camera moves that are not real, and if you take them out, the story is still what it is. In this film, if it weren’t for the effects, the story would be different. Te effects had to be part of the narrative, especially with the director.” And because of that, once again, ILM pushed the state of the art of effects, particu- larly fire simulation and digital-double work, forward once again. n Barbara Robertson is an award-winning writer and a contributing editor for Computer Graphics World. She can be reached at BarbaraRR@comcast.net. July 2010 31