It took extensive coordination among several vendors to pull off Live Free or Die Hard, and Alain Bielik reports on the results.
Live Free or Die Hard (opening June 27 from Twentieth Century Fox) is the fourth installment of the popular Die Hard franchise. In this new adventure, Detective John McClane (Bruce Willis) confronts a group of cyber terrorists attempting to destroy the computer infrastructure of the U.S. When director Len Wiseman (Underworld) started working on the project, he decided to emphasize practical stunts and special effects, and to maintain a low profile on the visual effects. In a summer season filled with CG extravaganzas, he thought that a realistic approach would pay off, just like it did for Casino Royale, which jumpstarted the James Bond franchise with record box office success. And, like the latest 007 installment, he still ended up with several hundred visual effects shots in his final cut.
Overall visual effects supervisor Pat McClung coordinated the effort, dispatching shots and sequences between several facilities, including lead vendors The Orphanage and Digital Dimension, additional vendors R!ot, Pixel Magic, Amalgamated Pixels and miniature effects facilities Cinema Production Services and New Deal Studios.
At The Orphanage, vfx supervisor Matthew Hendershot and vfx producer Joel Mendias faced the tightest schedule of their careers. "We worked on two key sequences: the fight in the elevator shaft, and the climactic battle between McClane and a F-35 fighter jet," Hendershot explains. "The end sequence was completely revamped very late in production. We actually received the plates in late March and early April for a May delivery! Not only did we get the plates much later than expected, but also the new ending required much more ambitious visual effects, including full 3D environments. So, we had to do a lot more within a shorter deadline..."
The end sequence involves a F-35 jet trying to take down a semi-truck driven by McClane on a freeeway. The airplane was built as a CG model, a nine-foot practical miniature, and a full size prop mounted on a motion base. At The Orphanage, CG artists started building the model in November 2006, but ongoing design changes on the full-size prop kept the modeling team busy until February 2007. The digital F-35 was built, rigged and animated in Maya. Textures were derived from photographic references, and global illumination was used to obtain highly realistic renders in mental ray. A combination of bump and displacement maps was employed to create surface irregularities.
"Ideally, one of the three models should have driven the other two in terms of look and texture, but the schedule didn't allow for it," Hendershot notes. "As we were finishing our model and textures, there would be changes happening to the design of the full size and miniature jets that we would need to address. Ultimately, the three units had to work simultaneously, each making adjustments as changes were made elsewhere, according to our client's direction. We even found ourselves in the situation where we had to deliver trailer shots with the F-35 while they were still finalizing the full size model!"
In several shots, the jet showcases its hovering abilities. The eerie flight maneuver required the development of a specific vertical heat ripple. A particle animation was created in Maya to displace and blur the background in the composite. Although a lot of time and effort had been invested in developing a realistic look, the director ultimately preferred to see much less of it. In the end, the effect was toned down to the point where it is now noticeable in a handful of shots only.
Wreaking Havoc on a Freeway
The chase climaxes when McClane reaches a multi-level freeway interchange -- a sequence that was added very late in production. The Orphanage was asked in December 2006 to create the fictitious interchange and its environment digitally. The only real section was a 1,000-foot long spiral ramp that was built as a full-size set in front of a giant bluescreen. There again, in order to be ready when the first plates would be delivered in late March, modelers had to start building the location while the set was still under construction...
The environment was created using 3D matte paintings. "Our matte artists painted key views of the environment, and camera-projected them onto relatively light geometry in Maya, although the size and scope of the environment still made for a pretty heavy model," Hendershot observes. "Once the projection cameras and their associated images were set up, the projections themselves could be rendered in comp for each shot. Live Free or Die Hard was the first project at The Orphanage to use Nuke for compositing. Its powerful 3D capabilities were a true asset to our show, and allowed us to simplify the process. Instead of having a technical director project and render every environment painting, the paintings could be passed directly to the compositor -- along with a projection camera and the matchmove camera. By turning over images and cameras from painters to compositors, we were able to remove one person from the process. Ultimately, the size of the paintings and geometry became too cumbersome to keep all live all the time. Compositors frequently had to pre-render their own projections from Nuke to ease the process. Still, I think it was very helpful to use this approach."
Combining 3D Packages
Two different 3D pipelines were employed to create the overpass sequence. Shots featuring the freeway in its regular condition were created within Maya and mental ray, using global illumination and final gather. Whenever the structure had to explode or collapse, the team used Houdini associated with Mantra. "Initially, we did many tests with rigid body dynamics to animate the destructions," Hendershot explains. "We obtained very nice results, but in the end, we found that this approach took too long. Instead, we opted to employ keyframe animation, using the rigid body dynamics tests as a reference to animate the main chunks of concrete.
"First, we broke the freeway geometry in Houdini, using cracking tools that were developed to create detailed broken geometry. Then, the geometry was rigged and hand-animated in Maya, mainly because our artists are more familiar with this package. Once the key animation was approved, we brought it back in Houdini to create secondary animation. We generated data that would indicate when two pieces of concrete would separate, when another piece would hit the ground -- basically, any kind of interaction between the hero elements. Houdini allowed us to use this huge amount of data to trigger many dust and debris explosions, and local changes to textures, all procedurally. For this type of work, we found that procedural techniques are much easier to employ in Houdini than they are in Maya. Houdini allows the artist to easily manipulate geometry directly in ways that most packages reserve for their particle tools." CG supervisor Dong Yeop Shin oversaw the development of most of the Houdini fx animation.
Led by lead CG artists Steve Cho, Josh Cole, Steve DeLuca and Kyle McCulloch, the compositing team faced tricky challenges with this sequence. Practical explosions and bullet impacts generated huge clouds of dust that had to be extracted from the plate, and brought back onto the CG environment. In many cases, the blue-screen didn't reach the top of the frame, which obliged the compositors to deal with dust clouds moving over a line separating the blue screen from a clear bright sky... The most complex collapsing freeway shots comprised of more than 100 layers.
Compared to the climax, the elevator sequence was more straightforward. During the course of action, two characters and their SUV crash into an elevator shaft. The sequence was shot in a five-story high set that was extended downward to create a sense of vertigo. Working from The Orphanage's Vancouver studio, CG supervisor Richard Sur and his team used Maya and mental ray to build a seamless extension. In addition, large rigs were removed from the SUV and the actors, and dangling elevator cables were extended. In some cases, original cables were entirely replaced with an animated CG cable.
A Shared Effort
Meanwhile, at Digital Dimension, a team led by compositing supervisor Erik Bruhwiler and 3D supervisor Andrew Roberts was just as busy crafting almost 200 shots. Digital Fusion was used for compositing and wire/rig removal, while the bulk of the 3D work was completed in 3ds Max.
In a major but low key visual effects sequence, a huge crowd is seen evacuating Washington D.C. "Given the restrictions of shooting at well-known government buildings, the production opted for a CG crowd," Roberts says. "We shot front, back and side photos of extras on set, and used those images to texture our Massive agents. Textures were cleaned up in PhotoShop and applied to a library of businessmen and women. Then, using SynthEyes, we 3D tracked the cameras for a number of crowd shots, creating low poly geometry matching the buildings, ground plane, stairs, and any obstacles seen in the plate. This geometry was brought into Massive and served as the terrain over which the crowd would move. To give our compositors full control to finesse our renders, we provided a number of passes and mattes. In some of the shots, we have close to 1,000 CG people moving through the scene!"
CG artists then turned their attention to cars and vehicles with a dramatic sequence in which every traffic light turns green... Wiseman wanted to depict car crashes from a variety of vantage points -- from car hood level hero crashes to overhead views with multi-intersection pileups. To create the sequence, Digital Dimension used a variety of techniques, including rigid-body dynamics and key frame animation. "We rigged the vehicles so that any animator could easily create realistic suspension behavior, taking into account the center of gravity, ground friction, etc." Roberts notes. "We used image based lighting (which had been acquired on location during principal photography), and selectively modeled portions of the scenes for the cars to more accurately reflect their surroundings, as dictated by proximity to buildings or other obstacles."
No Way Out
In the most spectacular sequence tackled by Digital Dimension, McClane and another character are trapped in a car tunnel, trying to evade a sniper in a helicopter. The plates were shot in an underpass that was normally used for deliveries. "Whenever the camera pointed deeper into the tunnel in our shots, we tracked in a CG tunnel rendered image, or an animation where the camera traveled down the tunnel," Bruhwiler explains. "Some of the tunnel extensions had to be accomplished through a cracked windshield, with flickering light as the car races down the tunnel, and with crashed cars, flashing lights and smoke zipping by. Very challenging! Extensive and challenging wire and rig removal was required for all of the stunt action."
The 3D team worked from blueprints and reference photos to create a 250-foot tunnel section. The CG environment was specifically designed to be tiled many times to reach any desired length. The final renders proved so seamless that, in addition to using the tunnel for set extensions, it was also employed as a hero environment for some shots. Depending on the type of camera move, the team would either 3D track the shot and render the tunnel through the moving camera, or for gentler moves, render a still frame for compositors to track in Digital Fusion.
Enhancing Practical Stunts
At one point in the sequence, the two lead characters are nearly crushed by a car that flips over in their direction and miraculously lands on two vehicles that drive past them. Interestingly enough, the car flip was realized as a practical stunt, not via CG animation. The two cars on either side of the characters were pulled along by a cable pulley system. The car flipping through the air was suspended by a cable that was passed through a gap in the roof of the tunnel location, attached to a large crane. All three cars were filmed simultaneously in camera for the hero element.
After the rig and cable removal was complete, the actors were integrated into the shot. "They had been filmed in a separate pass, and needed to be rotoscoped out and then tracked into the background plate," notes lead compositor Ryan Smolarek. "To really immerse the characters in the scene, additional CG debris was added. Because the roof of the location was not actually fully enclosed, the scene was treated to hide areas exposed to the sky and to remove as much light as possible, as to sell the idea that it was really a tunnel."
In the most publicized shot of the movie, McClane finally manages to launch his car at the helicopter and to destroy it. The remarkable stunt was completely captured in camera. The car was propelled into the air by two powerful nitrogen ratchets, and impacted the helicopter that was dangling from a 100-foot crane. Digital Dimension was then asked to paint out the rigs and crewmembers, to add a CG rotor, and to create a split composite with a stunt man jumping from the helicopter at the last second.
Playing with Models
In the film's most shocking moment, the Capitol building gets destroyed. The landmark construction was a practical miniature element that was composited into a plate of the real Capitol building. Two different takes of the model explosions were combined to create the massive blast. The effect was then enhanced with CG smoke elements, practical tree models reacting to the explosion, and matting to keep the debris near the building.
A practical model was also used for a scene in which a power plant is destroyed, but this time, the explosion only required minor enhancements. "To help depict tons of concrete falling from the roof of the collapsing power plant, as seen from the inside, we developed a debris system which included controls for debris speed, direction, rotation and debris content," says Roberts. "This enabled our artists to dial in the right proportion of concrete, wood and pipes to the director's satisfaction. In particular, he wanted to see hero slabs of concrete to tie the shots in closely with live action props seen later in the sequence. These debris elements were meticulously modeled and textured with procedural displacement shaders to ensure they held up close to camera."
A Coordination Feat
At The Orphanage, Hendershot will definitely remember Live Free or Die Hard as a dramatic race against time. "The production team really made a massive effort to make it happen. It took such extensive coordination to allow so many things to happen in parallel, just to get the shots done in time."
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.