It wasn't supposed to take two and a half years or be this complicated, but in the end, after production snafus, cost-overruns and reshooting the entire third act, they finally got the zombies they wanted for World War Z. But there were a few casualties along the way over "creative differences," including Oscar-winning VFX supervisor John Nelson (Gladiator), who was replaced in post by Scott Farrar (The Transformers franchise), on loan from ILM.
"The whole movie had been shot when I came in and I just saw that director Marc [Forster] needed some simple things to help put his movie together," recalls Farrar. "We talked about what's working and what's not working. I said to him, 'Don't worry about how we're going to do it. It's not about technical stuff at all. If you have previs or postvis or any vis, let's only cut in the things you really like and if we're missing something, we'll make it. Let's do a rough edit."
What Farrar especially liked was the concept of the zombies as very fast predators who travel in hordes. He found this uniquely exciting. But it was only touched on in the footage. So Farrar went back and studied the artwork of Framestore VFX art director Kevin Jenkins and realized that some of his best ideas hadn't gotten into the film yet.
"Let's design the shots so we see the behavior," he continues. "If you're going to have an ant pile of zombies climb up a wall, let's see how it forms, let's see how they do it, let's explain that to the audience; let's plus it out."
Meanwhile, animation supervisor Andy Jones had already begun setting the rules of zombie behavior, where they not only run fast but also lead with their heads. They crawl all over each other and fall off buildings without a care in the world because they're impervious to pain. But this needed to be explored more in stages. Jones oversaw Mocap sessions with contortionist dancers and live actors and most of this was done by MPC, which was on the project from the beginning. So were Framestore and Cinesite.
"The goal was to be true the rule sets that we came up with," Farrar suggests. "It forces you to make changes in story points. Brad Pitt was supportive of all this. It gave him something to play against dramatically. He was concerned about being clear to the audience."
MPC, under the supervision of Jessica Norman, concentrated on the hordes of zombies in Jerusalem (shot in Malta) where they form pyramids and tentacle-like shapes, the suspenseful plane crash and the epilogue, which not only contains pyramids but also explosive action.
There was both close-up and crowd work, which was complex because of the various formations and actions. Some of the hardest shots were put on hold and completed later after the reshoots when Farrar came aboard.
"Marc was interested in the realistic side but when we see them en masse, we were interested in the pyramid shapes they would take so we looked at concept images and reference material of insects and schools of fish," Norman explains. "For Mocap editing we used MotionBuilder and crowd simulation was done using ALICE, our in-house crowd tool. We started out capturing a lot of Mocap, which we used in the crowd scenes and some for the hero performances with animated close-ups."
Part of the animation challenge was to match the movements of the live action performers and take them a step further. They would keep on running even when their limbs were broken.
"Typically, the workflow for these bigger crowds would be to first try and establish the shape and the speed," Norman continues. "The layers are so complex. Sometimes we would use animation to help design 3D volumes and then we would use those initial layers in our crowd system to populate the crowds. For the pyramids, we shot MoCap clips of guys climbing up on nets. And you'd get similar actions of what we needed and then ALICE would place them based on information and work out the interaction between them."
The larger pyramids typically included around 5,000 agents. Once the pyramids were populated, the detailing was worked on, adding animation vignettes with zombies interacting and falling as well as the various actions needed on the ground. For falling and landing zombies, they used Papi, the in-house rigid body dynamic solver based on the Havoc engine.
MPC's modeling team built unique humans and zombies using reference photography and scans gathered on set. There were 24 different body types: men women and children with different texture variations. Each character was built as human, and at three different levels of zombification. Level 1 consisted of zombies that had just been bitten, level 2 was half-way there and level 3 was complete zombification with missing hair, defined veins and wounds. In addition, each character was also built at four different levels of detail from close up to long distance.
Clothing was built to match the different zombification levels: dirty and torn for level three and clean for humans. Once built, 3,000 crowd variables were decided on but with flexibility for change in tops or trousers for any character. For the large crowds, MPC's asset team created an even bigger wardrobe.
The environment team created 2.5D matte paintings based on photography taken in Jerusalem. The team also built a 70-foot tall wall that was seen in many of the shots during the Jerusalem sequence. The wall was built using photographic references of small pieces of set wall as well as various other concrete build reference materials. Outside the wall MPC created a wasteland with derelict buildings. These were created using CG models, matte paintings and projection techniques.
Much of the plane sequence was shot inside a partial plane on a gimble rig. Aside from CG explosion, vapor and debris, there was enhancement of makeup on live action zombies, including the addition of veins and eye treatment.
"Andy and I wanted more people in makeup intermingled with CG zombies because one or the other by itself didn't look great," Farrar admits. "The strange thing was there are shots where the zombies looked too human, so we'd have to do these quirky movements to make sure the audience knows they're zombies.I want to create illusion and keep the audience guessing as to whether they were live actors or CG characters. A well executed illusion -- I'm in."
Bill Desowitz is former senior editor of AWN and VFXWorld and the owner of Immersed in Movies (www.billdesowitz.com). He's also a columnist for Thompson on Hollywood at Indiewire and contributing editor of Animation Scoop at Indiewire. Desowitz is additionally the author of James Bond Unmasked (www.jamesbondunmasked.com), which chronicles the 50-year evolution of 007 on screen, featuring interviews with all six actors.