World War Z

Cinesite VFX supervisor Matt Johnson was one of the first people involved in preproduction on ‘World War Z’ in April 2011, from preproduction throughout the shoot period. The story begins in Philadelphia, but the only photography actually captured there was undertaken by Matt & visual effects photographer Aviv Yaron during a comprehensive photo shoot. The action seen in Philadelphia was in fact shot in Glasgow, Scotl&.

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However, because discussions in pre-production had indicated the darker, moody 1970s thrillers as reference for the film’s looks, Cinesite’s work needed a naturalistic feel to fit into lớn that style, matching the DP’s handheld camera work. Therefore, an intensely real approach to lớn the environment became a major focus for the Cinesite team.

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Street Canyons

“We put a huge effort into lớn absolutely invisibly turning Glasgow inkhổng lồ Philadelphia,” Matt said. “Glasgow actually works very well for the first two stories, immediately surrounding the actors during the shoot. Historically the two cities’ architectural styles have a lot in comtháng, as their trade & finance developed in around the same era. But above sầu street cấp độ, the differences are more obvious. We needed to create those steel and glass ‘canyons’ that Philadelphia’s more recent architecture has created in its streets.”

When Matt & Aviv arrived in Philadelphia after the shoot in Glasgow, Matt had to lớn think ahead to lớn post production and devise a way of capturing shots that could be used lớn blend the locations together. He researched which buildings in Philadelphia were the most distinctive sầu, such as Comcast Tower, Union station and so on và incorporated these into lớn their Glasgow-Philly mash-up.

Views down the very tall canyon-lượt thích streets, showing cars stretching inlớn the distance, were carefully balanced - above sầu a certain height, even when cchiến bại lớn camera, the buildings were digital. “Our primary goal was to give the environment in each completed shot the same look as photography, not a CG render, in order to avoid attracting any undue attention away from the zombies & people. For the street level traffic jam, we found a good supply of American cars, taxis and ambulances in Glasgow, which we replicated và extended along the streets, plus digital people lớn fill out the ranks,” said Matt.

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Doing It for Real

“A lot depended on the thoroughness of our reference shoot. We went up on roofs và shot at all levels, across, sides & textures. Much earlier on we had considered a 3D build-out, but once we got to lớn Philadelphia I decided that as long as we were there, at the target location, we might as well capture everything in-camera and go for the ‘real’ approach, only relying on digital assets for the gaps, back-ups and blending.”

Tracking and match moving was an essential aspect of virtually every shot Cinesite worked on. Their decision lớn use real photography for environments demanded a precise fit in order lớn place it convincingly into the plate. “It’s one of those thankless tasks that never get noticed - until it’s been done wrong, of course, & then everyone sees it,” Matt remarked.

Thomas Dyg, environments supervisor, agreed that match moving và tracking the shots were critical for his team. “Not only did we need a precise line-up of photography khổng lồ the live action but we had khổng lồ carry the accuracy from the foreground into the background, using the full depth of the image,” he said. “In situations where you are tracking a character, for example, inkhổng lồ the foreground that you want the audience lớn watch, you focus all tracking effort at that depth, but here we were working very precisely straight through the images.”

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Photo lớn Mapping

Perfect photorealism based on the photography became their guiding light. Thomas explained, “We could base our two main environments, Philadelphia and New Jersey, on Matt và Aviv’s reference photos. The photos were all mapped onlớn simple geometry allowing them to lớn rotate & reposition the buildings, within reason, to lớn accommodate various camera angles while keeping the photorealism of the image itself.

“This was a huge benefit. While many environmental projects can be stylised to an extent in an effort lớn follow a story và the director’s ideas, this time the look had to lớn be realistic lớn the màn chơi of a documentary. You could say we were creating unreal events – zombie attacks – happening in a real world.” For example, in a sequence shot at a large square in Glasgow where a major confrontation occurs between zombies, traffic và people, the surrounding buildings the audience sees are images of actual, recognizable buildings và elements from Philadelphia, composited into lớn the plates to replace their Glasgow counterparts.

Thomas also said that traditionally, environment teams deconstruct photography & then re-build scenes with new textures, for example, or custom shaders and lighting rigs. “Instead, we could use the photographs virtually as they were, & spend our time on art direction and accuracy that would tư vấn the VFX, animation & CG teams’ zombie work,” he said.

A New Zombie

It would certainly be true that the crowds & actions of both humans and zombies are what so overwhelm the audience in nearly every sequence, starting in Philadelphia. As the street action gains momentum, the director did not want the audience khổng lồ be aware that they were watching a ‘zombie movie’, but khổng lồ remain unsure of what was causing the commotion – a riot perhaps, or civil unrest.

The four progressive sầu phases of zombie infection came into play at this point, as described by VFX supervisor Jessica Norman at MPC whose team defined the range of looks và behaviours <see Part 1 of this article>. Matt explained, “In Philadelphia the zombies were still in ‘phase one’, with a minimum cấp độ of physical deterioration. It gives viewers an awareness that the normal population were being chased by a different và dangerous group, và that feeling comes as much from their animation as their look. While the typical creatures of past zombie films slowly và relentlessly lumber along, these zombies have to be more immediately threatening và inescapable, rapidly advancing over large distances. Entirely new moves were called for, non-human, fast & lethal.

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Dance of Death

“In pre-production, experimental-style dancers were engaged và succeeded in giving us truly bizarre, other-worldly performances. They worked at length with the production lớn refine moves such as convulsions & flinging limbs. These were captured and used both as actual motion capture & as video reference for the animators, so that we could enhance our Massive sầu crowd simulations with incidental hand-animated actions & hero characters.

“The simulations we were generating for the crowd scenes could comprise combinations of both zombie & human characters, in which the zombies were given some subtle visual clues lượt thích darker colouring lớn mix them slightly apart. A matchmoving survey team travelled with Aviv and me on the photo shoots, accurately tracking ground planes và environmental obstacles to lớn allow the simulation crowds to run realistically through each scene.”

The way in which the zombies attack & bite became a particular focus both for Cinesite’s animation và CG teams. It was important khổng lồ get the look and moves right because their bite was their means of taking down và infecting their victims – & surviving. When seeking reference, the animators looked first at football & rugby tackles but noted that an unavoidable reflex makes people facing impact throw up their arms for protection, something a voracious, inhuman zombie would not bởi.

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Fearless

Realising that zombies need to lớn launch themselves teeth first inlớn an attaông xã, they found that the best reference were videos of some Israeli attachồng dogs that run and leap fearlessly, fangs bared. But they still had lớn transfer this action to lớn the human-based zombie animation. “Because it wasn’t feasible to expect any live performer to lớn do this, we had khổng lồ turn khổng lồ CG. This meant starting with shots of real stunt actors và then carrying out complete, full frame take-overs with a digital double for a few frames,” said Matt.

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“This wasn’t only a texturing, shading và lighting challenge but also involved cloth & hair simulations. Since zombies have sầu so much in common with people, viewers would quickly notice any inaccuracies during the multiple swaps between digital và real characters that some of these sequences needed. A cloth or hair sim might require numerous passes khổng lồ work with a character’s violent animations because hair & cloth had to lớn look very realistic but not obscure the critical part of the action that was telling the story.”

In some of the more violent zombie attachồng scenes out in the streets, digital human characters had khổng lồ be built as well, to run up in front of crashing vehicles, for example. Digital takeovers were often done with rotomation – that is, rotomating the live sầu action performance up lớn the point of handover to lớn a digital double - khổng lồ blover the two performances. Work on faces, such as partial replacements of zombie characteristics applied as digital makeup khổng lồ enhance the actors’ looks, were especially demanding. The eyes, jawline và other details would be rotomated lớn project baông xã onlớn the digital work for a perfect alignment.

Lighting and Rendering

CG Supervisor Anthony Zwartouw explained the influence of lighting & rendering on the effects in this film, & the efforts Cinesite made to tăng cấp their techniques. “Over the two year period we worked on the show, the pipeline team were making continuous improvements to lớn the skin, hair and cloth shaders we used for the anh hùng digital doubles và crowd characters,” he said.

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“Although Cinesite uses Renderman as its primary rendering package, the software is heavily modified khổng lồ integrate it into lớn the pipeline. For example, all Cinesite"s shaders are written from scratch by our own shader writing team. The lighting pipeline team - Alex Wilkie, Joe Gaffney & Ole Gulbrandsen - & I decided early on khổng lồ try lớn simplify our shaders to lớn make them more efficient & intuitive sầu for artists. We identified parameters that should be connected & merged them, which resulted in far leaner, easier lớn use shaders yielding better results in less time.”

Energy Conservation

They also developed co-shaders enabling the artist to plug in only the attributes that are specifically needed, rather than including all of them at once, which their previous monolithic shaders had required. Furthermore, the shaders were redesigned lớn mimic the real world more faithfully by adopting the principle of energy conservation. “As light – that is, energy - travels from its source and hits a surface,” Anthony explained, “it"s either absorbed, scattered as in diffuse or subsurface scenarios, or reflected. The sum of the reflected, scattered và the absorbed energy should equal the initial energy from the source.

“In previous shaders, it was possible khổng lồ have sầu an unrealistic situation where a material is reflecting, scattering và absorbing more energy than the light source is emitting, essentially creating energy out of thin air. A key benefit of this is the time the lighting TDs time can save when balancing shaders, producing more realistic results faster. The conservation of energy also led lớn more realistic behaviour in arbitrary lighting situations.”

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Fully Raytraced

Meanwhile, because the production extended over such a long period, not only was Cinesite making significant upgrades to lớn the lighting pipeline for other shows such as ‘Skyfall’, led by CG supervisor Axel Akesson, but numerous updates were also emerging for RenderMan’s software. “The biggest step was adopting a fully raytraced pipeline,” Anthony said. “The updated versions of RenderMan included a far more efficient & faster raytracer than before. In light of this, we in turn embraced an almost fully raytraced pipeline that allowed artists khổng lồ create more realistic images with accurate multiple bounce reflection và diffusion.

“Up until then, a lot of the passes such as indirect diffuse, subsurface scattering & ambient spherical harmonics were all calculated as pre-pass point caches. The caches were complicated, time consuming lớn phối up và often didn’t yield accurate results. A main quality slider control was adopted, which could be set between 0 and 1 lớn adjust the raytrace sampling in all areas, from shadows to reflections. It also culls certain computationally heavy features once the slider passes a certain point.”

The accumulation of these updates has led khổng lồ a more intuitive sầu environment for the team lớn light in. “An artist can import an asphối, add lights & achieve a far more realistic result straight away, without setting up cumbersome point cađậy pre-passes,” said Anthony.

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Invented Cityscape

A critical sequence takes place atop a housing project tenement building as the family of lead character Gerry Lane, pursued by violent zombies, rush desperately up a stairwell to meet a rescue helicopter that will airlift them out of the thành phố lớn safety. “The action was shot on a 360° green mix – a potential nightmare of a VFX scenario with only a small phối piece serving as the surface of the roof the actors stood on, completely surrounded by green screen. Every angle of every view you see, except the rescue helicopter craned in overhead, was digitally created,” Matt said.

Phokhổng lồ opportunities to lớn capture actual housing projects like this one were non-existent but, maintaining their aim khổng lồ avoid disruption of the environment inlớn the story, the team again chose khổng lồ invent this cityscape entirely from real elements. Consequently, after completing their shoot in Philadelphia, Matt và Aviv flew to lớn Thành Phố New York, shooting with the intention of gathering enough imagery to create the whole rooftop rescue sequence ‘for real’ – textures in particular.

Instead of recreating them in CG, they used the 3 chiều re-projection capabilities now available in Nuke. By working in this way, 3 chiều CG could be reserved for smaller objects but the bulk of the environmental work could still rely on photography. “The building the family stand on is based on buildings shot in Harlem, Thành Phố New York, while the immediately adjacent ones are from the Lower East Side of Manhatrã. In the distance, lớn keep our scene grounded in reality, we travelled lớn New Jersey and found a high rooftop that gave sầu us an effective view. From there, Aviv captured 360° or 180° panoramas using a rotating camera with a digitally tiling head,” Matt said.

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Over the edge

“As you can imagine, he & I spent a lot of time on the rooftops of America, shooting complete buildings at different heights lớn get the flat, side-on views for textures. In the end we had real, photographic components for the full environment, foreground through lớn the distant background, represented by the images from Harlem, Manhatrã and New Jersey.”

A key reason these environments had to lớn be as realistic as they were is that the action is not completely confined to the rooftop. The zombies shot in camera were joined by CG zombies, a number of which frantically run out of the stairwell & drop off the edge, attracting viewers’ eyes out inlớn the environment. One key shot is angled up, looking at zombies falling from the top of the building down towards the camera on the ground. This is an entirely digital shot, featuring a CG building façade, helicopter và animated digital zombies.

Safe Harbour

Towards the over of the film we see a flotilla of ships from the air, heading for a harbour. Matt shot the plates for the sequence from a helicopter flying off the coast of Cornwall. There was only one live action ship in these plates, a Royal Naval Reserve ship called the ‘Argus’ as it travelled from one port lớn Falmouth Harbour to be shot with actors on board as a part of the movie.

Once the Argus was moored in Falmouth Harbour, the action on deông chồng of about 100 real actors needed lớn be augmented with another 200 digital people. The existing harbour environment in the background had to be painted out, replaced và enhanced with numerous aircraft. In particular Cinesite’s team created a CG helicopter that landed và took off from the ship, a manoeuvre that would have sầu been too dangerous khổng lồ achieve with live sầu action due to the numbers of actors on mix.

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To build up a military encampment, created from a plate shot at Lulworth Cove and seen in one long shot as the camera passes overhead, still more military vehicles were needed, of course, plus many other environmental and CG refinements. Thomas Dyg described the work here. “The environment and CG teams combined forces again. The 3 chiều artists built some simple models for the buildings và vehicles, và textured and lit them in a generic way with lighting projections & shadows. Then our matte painters gave sầu them a weathered look and more detail,” he said.

“The camera passed over the buildings vehicles and people, then a small forest and then the cove sầu itself, constantly changing perspective sầu. Creating a scene like this, only seen once in this long shot in which the camera progressively changes its point of view, is very different to handling the đô thị and rooftop environments seen from multiple angles in multiple shots over time.”

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Stories Inside Stories

For the very wide shots showing aerial views of Philadelphia, the team removed the real traffic from the streets và motorways and replaced the cars with CG vehicles stuông chồng in a massive city-wide gridloông xã, adding smoke và explosions overhead. One such shot included not only the traffic jam but also hundreds of thousands of desperate people walking along the motorway in a mass exodus of humans.

Matt commented, “I wanted to create pockets of action to fill these shots with their own drama, và humanise the mass of people walking down motorways or across the bridge aước ao CG cars while explosions, fires & smoke rise over their heads. The audience could consider that while this movie follows the story of Brad’s family, meanwhile hundreds of other ‘movies’ are unfolding in every direction. Shots like this were what made ‘World War Z’ such a satisfying project. So much needed to lớn be digital, but remain in the background và enhance the story invisibly.” http://www.cinesite.com