Computer Graphics World

September 2009 28 n n n n CG Creatures When the look dev team began work- ing on the characters, they could reference HDR images taken on set, but didn't have test images that showed what the final look of the film would be. "We went outside to the Image Engine parking lot and took im- ages, and that's what we started with to do light and dark setups," Stewart says. "We tried to light in a neutral environment and then test it in the extreme." Getting correct colors for the aliens was particularly difficult. "Neill wanted Chris- topher and little CJ to look green and the rest of the characters to have realistic insect colors," Stewart says. "You wouldn't believe the shaders we didn't use." e lighters discovered, for example, that while iridescence looks great on little bugs, it looks like gasoline on six-foot-eight aliens. If they used rim light, it pulled the audience's attention from the story points. Plus, they needed to cover the creatures with mud and paint. "e director wanted the characters to resemble what Soweto actually is," Stew- art says. "He didn't have an art director on set or a visual effects supervisor. It was just us, so we were able to get into his head. We put artifacts everywhere, added tribal war paint, and he'd get more and more on- board. It was great to be part of that artistic decision-making process." Fitting In e compositors also often altered the look of the characters in e Foundry's Nuke after rendering. "We'd add semi-3D dings and other effects," Kaufman says. "One tool that the R&D department came up with let us add a shiny, wet look in the composite. Making sure the aliens would hold up and be photoreal was so impor- tant. ey're in the real world, an alternate world, but it should be completely normal where nothing stands out except there are giant aliens walking around." Special tools in Nuke also helped the paint and compositing teams create back- grounds hidden by Cope while in a gray suit on location. Even though the com- positors replaced Cope with an alien, be- cause the alien was a different size and the performance sometimes changed, the two didn't match. To remove the actor, the roto depart- ment used Silhouette Roto from Silhou- ette FX. en, the compositors worked with a clean plate shot without Cope to fix the background. "We had a tool that al- lowed us to quickly track the shots, bring the 3D camera into Nuke, and project the clean plate onto proxy geometry when we removed the actor," Walsh says. "at was a key part of the show." Of all the shots, Nichols ranks one of the starving, sick aliens in the mother ship early in the film as the most difficult. "It was a 100-alien shot, then a 1000-alien shot, then a million-alien shot," he says. "But the cool thing was that every animator contributed to it because they all had finished their oth- er shots." To create the aliens, the anima- tors generated motion cycles of aliens acting sick, coughing, rolling on the ground, and so forth, which the team placed on cards to create 2.5D shots. Spaceships Although Image Engine created the first designs for the mother ship, Weta Digital created the final three-mile-wide ship that hovers over Johannesburg during the film. Weta also worked on two sequences with a drop ship, and created the heads-up display for a robotic exo-suit. Matt Aitken led the visual effects team at Weta that worked on the 92 shots. "We were originally approached to do the lion's share of the VFX work on the show," Aitken says. "We did previz for the big fight sequence, and a hero model for the exo-suit the main character wears in the sequence, and we would have loved to have done the entire show, but with everything else [we had here] in-house, we had to politely decline. So, the main production work went off to Image Engine." Toward the end of production, however, District 9's producer and Weta owner, Peter Jackson, helped the studio find time in its schedule to help out with the ships and the suit. e challenge with the mother ship was in giving the gigantic spaceship a sense of scale, which the modelers, texture painters, and effects artists accomplished by adding details to the model and atmospheric ef- fects and haze to the sky between Johan- nesburg and the ship. For the heads-up display in the exo-suit, the trick was to create a cloud of informa- tion that Van De Merwe, who is wearing the suit, couldn't possibly understand. "at was Neill's overriding direction," Ait- Weta Digital created the complex computer-generated mother ship and the drop ship (not shown) that rises from underground.

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