The rage virus continues in 28 Weeks Later, and Alain Bielik uncovers the gritty vfx work turned in by a host of vendors under the supervision of Sean Mathiesen.
Aerial photography, CG animation and miniatures were elements used in 28 Weeks Later. Courtesy of RSP. All images & © 2007 20th Centu
28 Weeks Later (opening May 11 from Fox Atomic) is the sequel to Danny Boyle's sleeper hit 28 Days Later (2002). Six months after a powerful rage virus ravaged the British Isles, the U.S. Army comes to the rescue and secures an area of London to be re-populated. But the refugees soon face another deadly outbreak of rage...
Even though director Juan Carlos Fresnadillo maintained the low-key approach of the original movie, 28 Weeks Later was realized on a much larger scale. The final cut includes some 404 visual effects shots, all supervised by Sean Mathiesen. "We split the work over 11 different vendors," he says. "We worked with Rising Sun Pictures and Animal Logic in Australia, Lip Sync, The Senate, The Mill, Rushes, Framestore CFC, DNA, Tim Walton, my own company Chocolate Lab in London (we did all the sniper vision and CCTV shots), Prime Focus in London and India and, finally, Rainmaker in London and Canada. We had a 10-week prep time and four months of post-production. The initial idea was that everything should look as if we were making a documentary. We wanted to make the footage look real, which included using hand-held cameras. One of the most interesting ideas was to keep a rough edge to the visual effects, to give them some style."
The signature effect of both movies is the eerie vision of characters wandering around in deserted city streets. This effect involved erasing all signs of life in London using elaborate matte paintings, often projected onto geometries, to replace the busy streets with empty lanes and sidewalks. To help reduce the amount of work, plates were shot in the early morning on Sundays, mostly in the Financial District.
Sean Mathiesen supervised some 404 visual effects shots, split among 11 different vendors over a 10-week prep time and four months of post-production. The initial concept was to make the footage look like a documentary.
Creating a Wall of Fire in 2D
In the key vfx sequence, the U.S. Air Force destroys the Isle of Dogs, a London landmark location, using napalm to burn the infected in an attempt to control the rage virus. The sequence combines aerial unit photography, day for night, CG animation, miniatures, blue and greenscreen drama plates and huge amounts of fire and explosion elements. When the studio requested that the post-production was accelerated, Mathiesen had no choice but to divide up the sequence between a large number of companies, each handing less than a handful of shots. This obviously created potential continuity issues. "It was perhaps the most difficult sequence for me to keep a consistent quality throughout," Mathiesen acknowledges. "The director had a very strong vision: he didn't want a wall of fire à la Independence Day. He wanted the fire to flow through the city like blood flowing through veins and vessels. The idea was that we would destroy what was outside in the streets, keeping the buildings mostly intact. In a sense, our napalm was closer to the water in The Day After Tomorrow than to the fire in Independence Day."
The first step consisted of previsualizing the sequence in Cinema 4D, and then, flying over London in a helicopter to find matching camera angles, and shooting drama based on the previsualization. Depending on the shots, Mathiesen used aerial plates, plates at street levels, and plates featuring fully detailed miniatures. These were built at 1/4 scale by special effects supervisor Richard Conway and set up at 90°. "The camera was positioned above the model," Mathiesen continues. "When we turned up the gas burners at the bottom of the set up, the fire naturally went up the vertical miniature street, simulating a wall of fire traveling along a street. This footage was then combined with bluescreen plates of stuntmen running towards camera, first in normal costume, and then in a burning costume." Most of the compositing for the movie was handled in Shake.
After previsualizing the sequence in Cinema 4D, the vfx team flew over London in a helicopter to find matching camera angles and shot drama based on the previsualization. Courtesy of RSP.
For another series of shots, Mathiesen filmed 50 extras running down a real street from a camera placed 20 feet in the air. Then, the crew built a -scale bluescreen environment that was encased in a box. This miniature environment replicated the rough geometry and position of the live-action buildings. Mathiesen elected to use a blue environment, as opposed to black, because he felt the color would give a nice transparency to the edges of the fire. Once again, pyro charges were ignited at the base of the box, pushing the flames up through the bluescreen geometries. The footage was then composited over the live-action plate, with the miniature fire realistically engulfing the full size buildings. The resulting images were subtly enhanced with CG animation to improve the way the fire was interacting with the main building.
Parallel to this effort, Richard Conway and his team rigged hundreds of explosions to help Sean Mathiesen build a library of varied fire elements, using napalm, gasoline, propane gas, etc. "I wanted the napalm sequence to rely on 2D effects for the most part," Mathiesen notes. "Fire being a very organic element, I felt that we should base the effect on real fire, not on fluid simulation. This explosion library was used for almost all the aerial shots. The compositors inserted the flame elements into the city plates, using complex articulated mattes to make the fire flow through the streets." The elements were later used by all the vendors to help keep consistency across the entire sequence.
Particles on Fire
In the end, only two shots were based on particle simulation. "In those shots, we see the whole Isle of Dogs peninsula being engulfed in fire," Mathiesen continues. "We first match-moved the helicopter plate, and then animated a geometry moving down the streets. It was just a tube being extruded along a spline, which we rendered and used to create an animated high contrast particle map. That was then used to generate the fire simulation spreading through the streets. The final render was created using sprites, and then the animation was enhanced with real fire and smoke elements to take the 3D curse off of the 3D generated particles. Depending on the vendor, 3D animation was created in Maya or XSI, with rendering being mainly handled in RenderMan. In many shots, simulation was also used to add exploding windows and shattering glass.
The aftermath of the napalm attack is revealed when the camera flies over the destroyed area. The London destruction was created by Rising Sun Pictures from a non-destroyed London shot by helicopter was provided by production. Maya and 3Delight were used for all the 3D work, and Shake was the compositing package. "For tracking, we used boujou and Shake as our primary tools," says RSP's visual effects supervisor John Dietz. "boujou allowed us to generate a true 3D track that we could import into Maya or XSI, and also into Shake's multiplane feature. With this information in Shake, we could adjust elements whilst being sympathetic to issues such as parallax and perspective with relative ease, which really helped sell the shots. We were also able to bring in matte paintings rendered on 3D animated cards with different volumes of smoke, which we could further animate in 2D to a degree. This enabled us to give the impression of the burning elements moving at different speeds depending on factors such as wind direction."
Unable to shoot inside Wembley, Millennium Stadium was digitally altered to show Wembley in disrepair, six months after the apocalypse, with the pitch seriously overgrown and covered in weeds. Courtesy of Rainmaker.
Using the 3D functions within Shake, the team painted the buildings to give the impression they had been damaged by the napalm bombs. This ranged from scattering debris to simulating structural damage. This proved really efficient when the crew was faced with the problems of different heights of the buildings being affected in different ways, and keeping it consistent throughout the sequence. In the 3D passes that were provided, artists modeled a rough sketch of the city and used this to place low lying animated smoke and vaporous chemical clouds between the structures. They provided the 2D department with accurate mattes to separate them and treat them for different lighting situations, such as dusk. They also offered the option to simulate volumetric lighting if needed for harsh light that would be associated with the mid day sun.
As the main characters run from the infected, they end up in Regents Park where they hope to be air lifted to safety. But as expected, something goes wrong. In a last ditch attempt to save them, the pilot plows his helicopter directly into a rushing crowd of 75 infected, slicing, dicing and mincing them into a grisly mess. Oddly similar to a climactic scene in Grindhouse, this sequence involved 3D motion-captured animation by Animal Logic, a 3D helicopter, CG doubles, live-action plates, matte paintings and lots of blood-filled mannequins being blown up in front of a bluescreen or on location.
Rainmaker took the specific plates shot at Millennium and altered them in Photoshop to look like Wembley. Courtesy of Rainmaker.
Altering a Key Location
At the end of the film, the characters reach Wembley Stadium where they get into a helicopter and fly to safety -- or do they? The script required a helicopter to be filmed inside the unfinished Wembley national stadium in London, but the crew was never able to actually film at that location. Rainmaker was asked to put the sequence together, with vfx Supervisor Paddy Eason and vfx producer Nick Drew overseeing the effort.
"Wembley Stadium is an iconic place in the British psyche," Eason observes. "And what's more, it's currently under reconstruction. So, this is the first time the new stadium will have been seen in a movie. We had to show it in disrepair, six months after the apocalypse, with the pitch seriously overgrown, covered in weeds, moss growing on the hoardings, etc. Perhaps understandably, the owners of the stadium weren't too keen on giving the production access -- either to shoot the scene, or even to shoot 360° stills panoramas..."
The solution was to shoot another new stadium -- the Millennium Stadium in Cardiff -- and digitally alter it to make it look like a weathered and overgrown Wembley. The shots included establishing shots filmed with the cast in Cardiff, and also background plates for blue screen shots that were filmed in an open field. Taking advantage of the fact that the sequence had a locked cut, matte painting supervisor Ingo Putze took a digital Canon 5D camera off on a day trip to Cardiff to shoot specific plates for each angle, with an appropriate focal length, so there was no need to cover the full 360°.
DNA also contributed vfx work to 28 Weeks Later. Courtesy of DNA.
"Back at Rainmaker, we took these stills into Photoshop and made the stadium look like Wembley, including adding the giant WEMBLEY lettering on the seats at one end, shifting the arrangement of the stands here and there, changing the seats from red, green and blue to all red, and finally adding a patina of dirt and decay," Eason explains. "These new background plates were then handed off to our compositing team for insertion into the shots, using Shake. At this stage, we patched together moving grass elements to make the pitch look very overgrown, and some other moving elements like hanging power cables and tattered banners to give the plates a bit of life.
"Perhaps surprisingly, we didn't use any 3D. Doing everything in 2D is kind of a lost art, but it can be surprisingly effective," he adds with an ironic smirk. "Actually, there was one shot in another scene that included some 3D and matchmove. It was an aerial shot of the city lights going out. Using LightWave and boujou, we build 3D geometries and tracked them to help turn out the lights, patch in dark buildings, etc. All in all, the Wembley scene was a great one to work on. There's something rather grand and intimidating about a large sports stadium. It was fascinating to see how, once the backgrounds had been created and added to the shots, the whole scene acquired a completely different atmosphere and intensity."
Mixing Practical Effects with CG
In a last ditch attempt to stop our heroes, the Air Force tries to destroy them using an Apache Helicopter as they drive past Whitehall (where the Prime Minister lives) in their escape vehicle. This sequence involved 3D CG cars and helicopters, drama and action plates, and many 2D explosion and bullet impact elements shot on bluescreen.
"All the companies did fantastic work, and each did something that added just that little bit more to make the film something unusual and interesting," Mathiesen concludes. "Also, nearly everyone worked on the napalm sequence, and I think that's the sequence the film will be remembered for in the long run."
Alain Bielik is the founder and editor of renowned effects magazine S.F.X, published in France since 1991. He also contributes to various French publications, both print and online, and occasionally to Cinefex. In 2004, he organized a major special effects exhibition at the Musée International de la Miniature in Lyon, France.
