FXguide: Zombie Warfare

World War Z begins in Philadelphia where former United Nations worker Gerry Lane (Brad Pitt) is stuck in heavy traffic. Suddenly a large garbage truck takes out a police motorcyclist and the many cars around him. Gerry catches a glimpse of strange behavior as hordes of people escape what seem to be other crazed humans – soon revealed as zombies whose bites pass on these same characteristics. Escaping to a New Jersey rooftop, Gerry and his family are dramatically rescued by helicopter and taken to a flotilla of vessels off the coast, as cities burn and many more people are attacked and become zombies. Gerry then begins a worldwide journey, starting in Korea, to look for the source of the zombie outbreak. Cinesite handled effects for these sequences.

Scenes set in Philadelphia were filmed in Glasgow, Scotland. For the garbage truck shot, which is seen from inside Gerry’s Volvo and follows the truck as it ploughs through the cars, multiple plates came together to complete the startling scene. “Simon Crane, the second unit director, wanted to do both the stunts and shoot the plates at the same time,” says Cinesite visual effects supervisor Matt Johnson. “So what we had to do was work out a way to make this possible, because normally when you do plates like this you have a tracking vehicle and use say camera arrays. We couldn’t do this on this show because we had to shoot the plates the same time we were shooting the vehicle.”

To make it possible, Johnson and second unit DOP Igor Meglic devised a way to fit four different static cameras inside Gerry’s Volvo to cover the field of view. “Those had to be wedged within the driving vehicle itself and then blacked out to be able to shoot through the glass,” explains Johnson. “So we had four overlapping cameras that, when stitched together, would make that field of view. We never actually pan in real life, the pan is a creation of the blending of the four plates together.”

So the final shot was made up a greenscreen plate of Brad Pitt, four plates combined for the garbage truck (with a CG replacement for its front section that has been shot with a ‘cattle catcher’), a policeman element, a dummy/mannequin element, background buildings, and a windscreen raindrop element “because I got obsessed with raindrops on windows,” admits Johnson.

Zombies in Philly

As Gerry and his family retreat to the street, they see the zombies begin to attack others, and for the effects of their bite to take only seconds. Zombie actors were utilized on set in Glasgow and then highly supplemented with digital counterparts. Cinesite looked to reference from videos of attack dogs that would go straight fro the throat, and also sporting events such as rugby and NFL players for how humans leap.

“The interesting thing about when humans leap is,” notes Johnson, “there’s always some element of self-preservation however hard they’re going in – a tendency to go in with your arms or protect your head. We thought zombies wouldn’t care about that – they’d basically care about getting the bite in. But then we realized – if a stunt person does that, they’ll be dead. So that ended up becoming something we did in CG.”

Halon served as one of the main previs providers for World War Z, under the supervision of Previs Director Daniel Gregoire and supervisor Bradley Alexander. The team used a portable V CAM System on set to imagine scenes, also relying on mocap, virtual camera, MotionBuilder and Maya for previs and postvis work.

For digital zombies (and several humans), Cinesite developed a pipeline based on scans of actors on the set. “We had a system where I was given cards,” says Johnson, “and if I wanted somebody to be scanned or photographed I would tick this little box and I would hand the person this card which they would show to an AD and they would be taken off to this magical world of texture photography and scanning.”

Cinesite based their digital creations on concurrent work being done by MPC for the Israel sequences (see below), with the studio relying on a Maya/RenderMan pipeline, nCloth for cloth sims and Yeti from Peregrine Labs for hair. “We built 30 odd characters that were the human and the first stage of the zombies,” says CG supervisor Anthony Zwartouw. “We did a lot of internal work on our pipeline to push our cloth and our hair and also generally our lighting pipeline to achieve these characters. They had to serve as both crowd characters in their thousands but also close up. We also developed an interesting tool where we could take characters we’d sim’d in Massive and then upgrade them to do cloth sims and hair sims on top of it.”

Significant environment work to turn Glasgow into Philadelphia was also required. “It’s not quite as mad as it sounds,” jokes Johnson. “There are similarities between the cities, but we did a lot of building work, adding height to the Glasgow buildings and making geographical sense of the layout. Also, the film is very handheld and zoomy which became a huge tracking challenge. We mounted zoom encoders onto every camera – ARRI Alexas – and we also hard-mounted a fixed wide angle lense camera on everything to give us extra tracking information.”

The rooftop escape

With his UN connections, Gerry secures a chopper pick-up from atop a New Jersey apartment building. He and his family manage to just evade several zombies as the helicopter takes off and flies from the city to the flotilla of ships.

Plates for the rooftop were filmed on a soundstage in essentially a fully enclosed greenscreen box. Reference stills from Philadelphia and New York were then used to create backgrounds. “We basically made a virtual set and then photographed it with cameras within Nuke,” explains Johnson. “They shot also with a helicopter buck and then we added in the rotor blades. We’d make the puddles in the water wobble a bit and add in prop wash and venting of exhaust gases to make it feel as real as we possibly could, adding in things like chromatic aberrations and real lens flares.”

In the sequence, the zombies have no hesitation in launching themselves at the moving helicopter, even if it means falling several stories to the ground. Cinesite employed both live action and mocap’d zombie actors for these shots. “They actually went a little outside the box and had performance artists and ballet dancers and experimental dancers do some of the real and mocap performances,” says Johnson. “They can do the most freakishly weird things with their bodies. And then if they’re running towards the edge of a building – some of them are real and some are CG. And hopefully unless you see one plunging 500 feet below you won’t realize which one is which.”