Computer Graphics World

September 2009 26 n n n n CG Creatures a refugee camp. Two decades later, millions of aliens live and scavenge for food in what has become a harsh, garbage-strewn, dusty slum. Street signs read "No nonhuman loi- tering." e alien mother ship still hovers. When the mockumentary switches to present-day interviews, we meet Wikus Van De Merwe (actor Sharlto Copley), a spineless but eager corporate lackey who works for Multi-National United (MNU), the company hired to keep the aliens un- der control. MNU has decided to evict the aliens from their shantytown homes and relocate them to a concentration camp in the middle of nowhere. e company puts Van De Merwe in charge. While Van De Merwe organizes his troops, we meet the aliens Paul, Christo- pher Johnson, and little CJ, and learn that after 28 years, Christopher has created enough biofuel in his secret lab to power the mother ship. But, Van De Merwe ar- rives to evict them, discovers the biofuel, and accidentally splashes some on his face. e alien DNA begins taking over his body, which makes him especially valu- able to MNU: He is the only human (now, part-human) who can operate the aliens' bioweapons. When Van De Merwe escapes from the evil corporation's biolab, his only refuge is the aliens' camp. Chases ensue. Characters interact. Battles take place. All seen through the news footage, documen- tary-style camera, which keeps the audi- ence transfixed in the moment. Alien Motion is quick, handheld shooting style af- fected Image Engine's animation process in two ways. "Neill [Blomkamp] didn't want the aliens to move like guys in suits because they look different physically, but he also wanted their motion to be realistic to fit into the genre of the film," says Steve Nich- ols, animation supervisor. "We drained the BBC motion library for reference." To capture that realism, actor Jason Cope (who also played Grey Bradnam, UKNR chief correspondent) performed the parts of the adult hero aliens during filming while wearing a gray suit decorated with patterns. "Our idea was to have wit- ness cameras and on-set motion tracking," says Dan Kaufman, visual effects supervi- sor. "But, the documentary-style filmmak- ing made it too difficult to put our cameras in good locations for triangulation. e cameras were in frame all the time." us, the animators instead started with rotomation, that is, copying Cope's action from the filmed plate onto the CG aliens. is provided the believable interaction between hero aliens and actors on set that the animators and Blomkamp wanted. For aliens moving in the background, the animators used motion data captured from Cope and stunt actors. "is movie is so different from other sci-fi films in which aliens roar, run, attack," Nichols says. "We wanted to show what it's like to live in a slum. So we have wounded and hurt aliens sitting down, lying on a wall, acting aggressively, dying, and rummaging through the trash." Data captured from a child helped the animators perform little CJ. "It took lots of reference to nail a six-year-old and not caricature him," Nichols says. "But, we still had to make him a bug." At first, the animators matched the rotoscoped and motion-captured perfor- mances exactly, but the aliens looked too human. "It didn't work for these massive bugs," Nichols says. To compensate for the size, the anima- tors tried having Cope wear stilts at one point to lift him to Christopher Johnson's six-foot-eight-inch height, but exactly matching that motion produced an alien that looked like it was walking on stilts, which didn't work. "We wanted them to be completely unpredictable," Kaufman says. "Most of the time, they're on two legs, but some- times they're on all fours, scrambling like chimpanzees. Sometimes they act all wild. And, their legs are like dog legs. So it was better to scale up the motion than to have stilts." Ultimately, the animators used key- framing to add the physicality Blom- kamp wanted for the skeletal creatures. Special rigs helped. "When we maneu- vered the data into [Autodesk's] Maya," Kaufman says, "we corrected for the dif- ference in how the joints in the legs fit together, and added more movement to the lowest joints." Once they achieved the overall perfor- mances, the animators gave the aliens little tics and other non-human behaviors that complemented their look. "We added in- Alien technology powers the robotic CG exo-suit created at The Embassy, which the protagonist Wikus Van De Merwe (Sharlto Copley) climbs into for the final battle.

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