After his recent success with MONSTER HOUSE, director Gil Kenan put his talents to work on this adaptation of the Jeanne DuPrau novel, CITY OF EMBER
. Together with Production Designer Martin Laing, the team set out to create a world where light is the lifeblood and a failing generator is the faintly beating heart of a dying race.
Luma was the lead vfx provider on the film, contributing more than 100 visual effects shots that run the gamut from full CG sets of amazing complexity to raging rapids and water simulations as well as a 9-foot mole that terrorizes the film's young cast.
Luma has grown significantly since its first steps into vfx with UNDERWORLD and THE HUMAN STAIN and has built a robust and powerful pipeline capable of handling the most complex and challenging shots in the film. "Nothing in this package is 'assembly line,'" noted Luma Pictures Visual Effects Supervisor Vincent Cirelli. "Every shot is customized. Every department was fully engaged in the project and they had to communicate at a very high level to make all the pieces fit."
CITY OF EMBER is set in a subterranean world that appears to be coming apart at the seams, and the tale turns on the effort of two kids to save the city. At the heart of the city is an enormous water powered generator that has been in operation for 200 years and has fallen into disrepair, its gears binding and oil spewing from its leaking joints.
For the production, a small section base of the generator room was built practically, but the bulk of it, stretching some five stories into the air and extending for hundreds of feet along the main waterway, is CG. "Often you can get away with building only what you need for the camera, but in this case the cameras went everywhere," Cirelli noted. "In addition, there were a number of completely CG shots in the machine room, where the moving pipes and pistons of the generator are located, with the only practical element being a ladder for the actors to climb."
The concept design was the primarily the work of production designer Martin Laing, but it fell to Luma to flesh out the finer details of the behemoth, a task it undertook with characteristic zeal. "We have a fantastic lead environment artist in house, Chris Sage, who came to Luma from an architectural background, and that was essential to creating something like this," Cirelli said. "This isn't about creating images, it's more like creating an actual functioning machine. Every detail of the plant has a purpose and a function."
"All of the CG objects have a history," explained Luma VFX Supervising Producer Steven Swanson. "We imagined what would happen to it through nearly 200 years of oil, grease and corrosion. And it's not just part of the design... it's also evident in the animation. The gears wobble, the cables are no longer locked down. Steam is pushing out and oil is oozing."
Equally impressive in scope are Luma's water simulations. The film's heroes make their escape from the city in a crude canoe that barrels down a tunnel on the back of a raging torrent of water. The water-every drop of it-is CG. Water is something that sets Luma apart from other studios, according to Cirelli. "Over the course of several projects that required CG water, we have refined a skill set that allows us to handle a large number of shots where water is one of the lead characters"
Cirelli noted that "most CG water effects fall into one of two categories: large bodies of water that convey volume and general motion, but obscure smaller details and small water systems with details down to the droplets of water and spray coming from turbulence. CITY OF EMBER required both."
Simulating a river full of rapids requires a level of detail that demands intense computing power and planning. "In order to create such imagery, we needed to create a processes and proprietary tools that would allow us to sculpt the simulation. Because simulations are based on physics, they generally do not cooperate when trying to attain very specific art direction."
Because of the enormous computing resources required for the simulations, Luma broke the task into a number of component parts. It first created low resolution versions of each shot in order to determine the proper volume and velocity and later rendered the scenes out in full detail (occupying several terabytes of data, some shots took several weeks to simulate and render). To add additional realism, a team of FX animators worked solely on foam, spray and interactive splash elements.
Additionally, Luma devised a unique system for rendering only those aspects of the simulation it needed. "One technique was called the 'frustum clipper' which allowed us to cut off details not visible to the camera," Cirelli said. "If we didn't need to see the simulation that was around a corner, we didn't calculate it. We'd wait until we got there. It was a modular approach."
Integrating the live talent into the CG tunnel sequence required some ingenuity. The actors were shot against green screen and Luma devised a way to apply motion data from animation onto a gimbal rig that controlled the motion of the real boat.
"This motion data along with animatics of the actual film set helped articulate the physical camera's relationship to the stationary boat and ultimately recreate the dynamic spirit of the previz," Swanson explained. "We then tightly match-moved the actors' in order to generate three dimensional shading. This in turn allowed us to composite the live action plates into the mottled light and shadow of the tunnel."
Among the most memorable features of the film is a giant mole that bursts through floors and walls in a ravenous search for anything to eat including the stories main characters. Based on a real-world animal called a star nose mole, the design considers what might happen to this tiny creature if it were left with no natural enemies for centuries. The result is a massive lumbering beast crowned with pink, finger-like nose tentacles that squirm and thrash about with creepy effect.
"The director, Gil Kenan wanted the nose to tell the story," recalled Raphael Pimentel, Animation Supervisor. "The creature uses it to sniff the air and it's the thing that telegraphs information to the rest of the body. The nose moves, then the body follows."
Luma made use of a variety of real world references in designing the look and action of the creature. Its lurching motion, for example, is modeled after a sea lion. Its claws provide the ripping force necessary to tunnel through dirt and rock. "It needed to have enough speed and agility to keep up with the kids, but at the same time had to express its girth and weight. We didn't want the body to move in a rigid way, but it also couldn't roll or bunch. We needed it to move like a pillow sack filled with lard." Pimentel observed. "The end result is a heavy and desperate motion that makes for a very interesting creature"
Making the mole look realistic at its larger size was also a challenge, added Cirelli, "Details in the skin of an animal are proportional to its scale and you have to take that into account when they become gigantic. You can't just make everything larger, you have to take into account what the larger animal is interacting with in its environment and how that might affect the skin and fur."
Although Luma has had previous experience with effects similar to all those employed in CITY OF EMBER the combination and larger scale made the project unique, noted Cirelli. "Over the years we have taken on projects that have allowed us to not only to expand the capabilities of our pipeline but improve the skills of our staff as well. We are continually impressed with the ability of our team to rise to any challenge that we put in front of them, they are a great group to work with and we are always proud of their achievements."
Credits for Luma Pictures go to Payam Shohadai, Exec Visual Effects Supervisor; Vincent Cirelli, Visual Effects Supervisor; Steven Swanson, VFX Supervising Producer; Justin Johnson, Digital Effects Supervisor; Pavel Pranevsky, CG Supervisor; Chris Sage, Lead Environment Artist and Raphael Pimentel, Animation Supervisor.
Luma Pictures served as lead visual effects provider on multiple Academy Award winner NO COUNTRY FOR OLD MEN (Paramount Vantage), as well as recent releases such as HANCOCK (Columbia Pictures) and PIRATES OF THE CARIBBEAN: AT WORLDS END (Walt Disney Pictures) . Some of the studio's other credits include APOCALYPTO (Buena Vista/Icon) and UNDERWORLD: EVOLUTION (ScreenGems/Lakeshore).