Alien Achievement
Issue: Volume: 32 Issue: 9 (Sep. 2009)

Alien Achievement

The word “Oscar” buzzed around the surprise sci-fi hit District 9 within days of its opening. Filmed in South Africa with postproduction in New Zealand and British Columbia, the low-budget TriStar feature flew to number one at the box office on opening weekend. Critics loved it, too, giving it an average 88 percent approval rating at the Rotten Tomatoes Web site, a rarity for a film starring aliens. The consensus: “technically brilliant and emotionally wrenching.”

David Edelstein of New York Magazine stated, “To call this the best shrimp-from-outer-space South African apartheid allegory ever made does not begin to do it justice. But it’s a start.”

AO Scott of The New York Times wrote, “In the midst of it all, you almost take for granted the carefully rendered details of the setting, the tightness of the editing, and the inventiveness of the special effects.”

An MNU officer holds a computer-generated alien, created at Image Engine, at gunpoint.

Steven Rea, critic with the Philadelphia Inquirer, agreed: “What is absolutely impressive are the visual effects: the hordes of aliens, the mother ship, the seamless blending of the real with the fantastic.”

High praise for any visual effects film. Outstanding for one made with a $30 million budget. Remarkable for a low-budget movie starring three CG characters and hundreds of CG secondary characters.

The CG characters are the aliens, disgusting creatures that look like a cross between a seven-foot-tall grasshopper and a lobster. They speak alienese, clicks and clacks that the South Africans understand and that the audience sees translated into subtitles. The hero aliens are a father and son, Christopher Johnson and little CJ, and Christopher’s friend Paul.

Image Engine, a relatively small visual effects studio in Vancouver, British Columbia, created all the aliens, which are always CG. The Embassy, also in Vancouver, created an exo-suit that plays a big role in the film’s climax. Weta Digital in Wellington, New Zealand, created the spaceships.

Based on writer/director Neill Blomkamp’s short film “Alive in Joburg,” District 9 is the first feature the 29-year-old had directed. Blomkamp, an award-winning visual effects supervisor, was raised in South Africa and graduated from the Vancouver Film School’s 3D Animation and Visual Effects program in 1998. He created District 9 using a blend of invented documentary, corporate video, television news coverage, and live-action footage shot as if by a camera operator on the run. Image Engine inserted its CG aliens into it all.

The film begins as a mockumentary, with talking heads analyzing and video footage documenting the arrival of an alien spaceship 28 years prior. We learn that when the ship arrived, it hovered over Johannesburg because it ran out of gas. When the South Africans became brave enough to pry open a door, they discovered thousands of starving, sick, half-dead aliens. They segregated them into 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 loitering.” The 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 under control. MNU has decided to evict the aliens from their shantytown homes and relocate them to a concentration camp in the middle of nowhere. The company puts Van De Merwe in charge.

While Van De Merwe organizes his troops, we meet the aliens Paul, Christopher 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 arrives to evict them, discovers the biofuel, and accidentally splashes some on his face. The alien DNA begins taking over his body, which makes him especially valuable 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, documentary-style camera, which keeps the audience transfixed in the moment.

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.

Alien Motion
This quick, handheld shooting style affected 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 Nichols, 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 witness cameras and on-set motion tracking,” says Dan Kaufman, visual effects supervisor. “But, the documentary-style filmmaking made it too difficult to put our cameras in good locations for triangulation. The cameras were in frame all the time.”

Thus, the animators instead started with rotomation, that is, copying Cope’s action from the filmed plate onto the CG aliens. This 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. “This 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 performances exactly, but the aliens looked too human. “It didn’t work for these massive bugs,” Nichols says.

To compensate for the size, the animators 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 sometimes 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 keyframing to add the physicality Blomkamp wanted for the skeletal creatures. Special rigs helped. “When we maneuvered the data into [Autodesk’s] Maya,” Kaufman says, “we corrected for the difference in how the joints in the legs fit together, and added more movement to the lowest joints.”

Once they achieved the overall performances, the animators gave the aliens little tics and other non-human behaviors that complemented their look. “We added insect jitters,” Nichols says, “fast, razor-sharp, hyper-real movements. The aliens have the physicality of humans but with extra twitches and fast motions that humans couldn’t do.”

Only a Mother Could Love

Initially, Image Engine scanned a maquette created by Weta Workshop, and created the 3D hero alien model from that. But during postproduction, Blomkamp asked the modelers to make the characters more insect-like, particularly the faces, and the aliens evolved into the grotesque grasshopper/lobster creatures that the humans in the film called “Prawns.”

“The original concept was a prosthetic outfit an actor would use on set,” Kaufman explains. “But the costume was bulky, and Neill wanted thin limbs, like an insect, skin-like cartilage, and so forth. But the biggest change, and one of the last things we did was make the face more insect-like yet capable of showing emotions and expressions we could recognize.”

Animators at Image Engine gave the alien Christopher Johnson emotional facial expressions by moving the plates that make up his face. Procedural animation helped move the tentacles.

James Stewart, creature supervisor, sculpted the new alien face to have small, interlocking plates that move to form expressions, and he led a modeling team that worked in Maya and Pixologic’s ZBrush to create the creatures in 3D. “I tried to have people focus on the construction, the lines of the polygons, to make sure they would deform correctly,” Stewart relays. “In modeling today, people sometimes create turntables without considering that the things have to move, articulate, talk, emote.”

Take, for example, laugh lines. For the face, modelers created what Stewart calls “subtle linear shapes.” “We animate faces muscle by muscle using linear shapes that can combine, but the root is simple,” he says. “For a laugh line, if you don’t build a shape with a crease down the middle, you can’t blend that shape into a realistic fold. On the other hand, if you make it too complicated, as you increase the deformation, it becomes tough to figure out which fold is what. So, we add shapes in an almost road map way—this area is that polygon.”

In addition, a proprietary tool called Mayhem handled the constantly moving tentacles and mandibles on the front of the aliens’ faces. “It does rigid-body dynamics,” says Shawn Walsh, executive producer. “But we used it to simulate these soft-body tentacles, so we could tailor the simulation and have control over close-up shots. We use this idea of jangling rigid-body objects against each other to drive a simulation in a number of ways.”

Image Engine also used Side Effects’ Houdini for volume rendering, footfalls, and dust hits, Next Limit’s RealFlow for fluids—spittle, vomiting, urine, and so forth—that helped make the aliens believable, and Maya’s nCloth, Houdini, and the rigid-body simulation for clothing and other soft bodies. A new project management tracking system, called Jabuka and developed by Image Engine’s R&D department, managed the hundreds of assets needed to create aliens with individual looks for the secondary characters, and provided shot continuity.

“We tried to create a diverse textural palette of aliens living in a Soweto-like place,” Walsh says, referring to Johannesburg’s infamous shanty-town. “Neill [Blomkamp] asked what we could do to bring them into the environment, and we started riffing on that idea.” They gave some aliens torn T-shirts and wrapped stuff around others’ arms; they imagined each alien would choose stuff it liked or needed. Some chose garbage bags. Some had splashes of paint and graffiti on their bodies. Others pasted skateboard stickers on their shells and wore hats.

“We had a number of hats in the asset management system and 12 different stickers,” Walsh says. “We could publish a set of assets with each character; it was literally like building a wardrobe that we could save on a shot-by-shot basis. This alien dressed like this exists in these three shots.”

On the Surface
Painted texture maps created in Adobe’s Photoshop and Maxon’s BodyPaint 3D combined to create varying patterns of color and displacement, as well as to provide lighting information for 3Delight, a RenderMan-compatible renderer from DNA Research. A “behemoth” shader provided controls for specular, wet specular, and so forth. “[The aliens’] necks had a wet, slug-like feel,” Stewart says. “To get that feeling and at the same time have the aliens look dirty without killing render times was a challenge.”

When the look dev team began working 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 images, 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 Christopher 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.”

The 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.

“The director wanted the characters to resemble what Soweto actually is,” Stewart 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 onboard. It was great to be part of that artistic decision-making process.”

Weta Digital created the complex computer-generated mother ship and the drop ship (not shown) that rises from underground.

Fitting In
The compositors also often altered the look of the characters in The 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 important. They’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 backgrounds hidden by Cope while in a gray suit on location. Even though the compositors replaced Cope with an alien, because the alien was a different size and the performance sometimes changed, the two didn’t match.

To remove the actor, the roto department used Silhouette Roto from Silhouette FX. Then, the compositors worked with a clean plate shot without Cope to fix the background. “We had a tool that allowed 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. “That 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 other shots.” To create the aliens, the animators 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.

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.

The 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 effects and haze to the sky between Johannesburg and the ship.

For the heads-up display in the exo-suit, the trick was to create a cloud of information that Van De Merwe, who is wearing the suit, couldn’t possibly understand. “That was Neill’s overriding direction,” Aitken says, “to make it not at all clear what the display is telling him, so that was fun.”

The drop-ship shots, on the other hand, were the most technically challenging. “There’s quite a long shot where the camera pulls back, the ground underneath a shack bulges, and the ship blasts up out of the ground,” Aitken describes. “Neill had brought a clip from Iraq of some troops driving along and an IED goes off. The IED was buried too deeply to damage the vehicle; it just created a spherical mound of earth. It was great reference for us.”

To re-create that effect and then have the ship break through, the crew started by animating the ship lifting up, and used that to determine how much dirt it would displace. Although simulation software moved the dirt, keyframe animation provided control over the timing.

“We used rigid-body simulation to crack a concrete layer into slabs, and those slabs effectively set off particle simulations for the dirt layers beneath,” Aitken says. “We do all this in stages, approving each stage as we go, and then building a new layer on top. There’s a high shot from a helicopter when we see the ship for the first time, and multiple dirt simulations as the ship shakes off all the dirt. And then we see the crater.”

Because the complex, multi-layered approach worked so well, Aitken decided not to add dust, even though the action happens in the middle of the day and in broad daylight. “There’s a tendency to obscure these big events with lots of dust, which tells you something big is happening,” he says. “But, it’s hard for the audience to see the details. So we decided to avoid that sleight of hand. We got great detailed behavior out of the layered approach to simulation.”

Battle Station
Ironically, while The Embassy provided Weta with a first pass at modeling the drop ship, Weta gave The Embassy an exo-suit model used in the final battle. “Originally, the exo-suit was like alien skin, but that changed, and it went toward a metallic creature,” says Winston Helgason, who supervised The Embassy’s work on location, while VFX supervisor Robert Habros oversaw the postproduction work at the studio.

The model, which the studio created using Auto­desk’s Softimage software, has panels that unfold so Van De Merwe can climb inside, and a complex system of guns and other moving pieces on the arms and legs. “We needed a detailed rig to move everything,” Helgason says. “Neill wanted us to convey the idea that Wikus [Van De Merwe] didn’t have full control and is awkward in the beginning.”

For texturing, the crew used Luxology’s Modo to lay out the UV maps and as a bridge between software programs, and ZBrush and Photoshop to create the textures. “Modo is great for prepping for painting,” Helgason says. Animators worked in Softimage, compositors in Apple’s Shake, and TDs sent files to Mental Images’ Mental Ray for rendering.

In addition to the exo-suit, The Embassy also created gun effects, bullet hits, and explosions, largely by adding elements in compositing. “We had tried to automate bullet hits for Iron Man,” Helgason says. “But, they didn’t look right. So we used real elements that we tracked into the right orientation to the camera, so each shot adds a couple days in compositing.”

Weta made the heads-up display inside the alien exo-suit confusing on purpose.

Similarly, the compositors added other elements shot on location to help give the film its R rating. “They shot squibs against a black background,” recalls Stephen Pepper, compositor. “When the exo-suit is firing its assault gun, we added muzzle flashes, and when it shoots a soldier, we added blood and guts. They filmed the soldier first, and then filmed a body bag filled with blood and guts that they exploded.”

Image Engine created a battle shot, as well, a bloody scene in which aliens rip apart a bad guy. “We set up a motion-capture rig to have the actors tear pieces off a body, and then the animators massaged that captured motion,” Nichols says. The result is a bloody, horrible shot.

“I love monster movies,” Nichols adds, “and this one definitely has a grisly gore factor that I don’t normally get to work on, something visceral that I haven’t experienced before. CG characters bleed, throw up, urinate, explode.”

Sci-fi Success
When Neill Blomkamp first approached Image Engine, the script had the studio simply inserting little insect-like characters into the scenes. “As it evolved, Peter Jackson and Neill pushed each other, and it became more of a character-driven piece,” Nichols says. “Neill’s wish was to have the film be about characters that happen to be aliens.”

Blomkamp got that wish, and much more, thanks to his creativity and with help from Image Engine, Weta, and The Embassy. In doing so, the District 9 teams created a unique movie that will go down in film history.

Barbara Robertson is an award-winning writer and a contributing editor for Computer Graphics World. She can be reached at