Framestore built the digital environments and CG doubles for the sequence in which Batman glides from a Hong Kong rooftop.

Visualizing the Invisible
Meanwhile, across the English Channel, Buf Compagnie had been called in, once again, to create highly stylized visual effects. On Batman Begins, Pierre Buffin's company had produced all the hallucinatory effects. This time, the Parisian team was assigned an even more intriguing concept: the "Spy Vision." In the movie, Bruce Wayne develops a new technology that is able to detect the electromagnetic waves emitted by cell phones. By scanning the waves' behavior in space, the device basically allows Wayne to visualize in three dimensions any environment in which a cell phone is turned on.

Since nothing like this exists in the real world, it was up to Pierre Buffin, Visual Effects Supervisor Dominique Vidal and their team to figure out what this technology could look like. "We started with the concept of the sonar: a device generates a wave that reveals all the volumes around it," Vidal remarks. "Except that you can't see a sonar wave. So, we did tons and tons of tests. We tried waves, metaballs, smoke, particles, etc. This process, partly supervised by Xavier Bec's research and development team, lasted eight months. In comparison, the actual creation of the shots took four months…

"Chris Nolan wanted the waves to bounce back on obstacles, but also to partly travel through them. In addition, the device needed to feel harmless, and not look like X-Ray. "We tried so many things, like how fast should the wave go, how much of it should bounce back, how fast it should dissipate, how it would dissipate, etc.," Vidal continues. "In the end, we managed to find the right combination of wave frequency, speed and rhythm. It was basically a CG wave on which we added some noise. All our work on the movie was created using proprietary software."

Working with VFX Producer Alain Lalanne, Buffin, Vidal and Nicolas Chevalier also designed the environments in which the wave animation was going to take place. The Spy Vision plays a key role in the Prewitt building sequence, in which Batman uses it to locate hostages. The device is also featured in the Batcave monitor room, where dozens of monitors visualize different locations -- an environment reminiscent of the Architect Room that Buf had created for The Matrix Reloaded.

The first step was to build each environment. Most of the time, it meant modeling layers upon layers of geometries, as, in the Spy Vision, all volumes are translucent except when hit by a wave. "We had to see across the rooms all the way through, including the city in the background with traffic in the streets, etc." Vidal remarks. "It was amazingly complex. And we had to do it for each one of the Spy Vision scenes in the monitor room. It was a huge endeavor for something that was only meant to be part of the background. In order to get enough material, we filmed our families, our apartments, our offices, etc. using video capture technology to have references for the key frame animations. The amount of work that those monitor room shots required was somehow insane!"

Buf also created the Batman logo animation that opens the movie in spectacular fashion.

Pioneering IMAX VFX
Just like Double Negative and Framestore, Buf had to deal with the fact that some of its shots were going to be rendered at IMAX resolution. For the three vendors, this unique requirement added an enormous challenge to an already very challenging project. Visual effects are usually created at a 2K resolution, very rarely at 4K, but full IMAX resolution exceeds 8K x 6K, with a single uncompressed frame representing around 200 Mb of data…

Double Negative produced the largest number of IMAX shots. "Early in the project, we took our crew along to our local IMAX screen to see The Dark Knight bank heist prologue in order to give everyone an idea of just what IMAX footage looks like," recalls Double Negative 2D Supervisor Andy Lockley. "Most people had seen upscaled IMAX films, such as Harry Potter and the Order of the Phoenix, but few had seen actual sourced IMAX footage. And when the first shot came onto the screen, there was an audible intake of breath… and a few worried faces in the audience."

At Double Negative, Jeff Clifford and the R&D department compiled a 64-bit compositing system with a streamlined set of tools, which allowed the team to access the extra memory that Shake required to be able handle the much heavier frames. "The amount of detail in the IMAX scans was frightening," Lockley continues. "You could see everything! It was like working on nine 2K shots tiled together. Looking on a monitor, you could keep zooming in, and more and more detail would reveal itself, so we really had to make sure that we didn't miss anything in the composites. A little edge that might seem insignificant on the monitor could potentially end up being five meters long (18 feet) when projected on an IMAX screen! After a series of tests, we determined that for most of the shots, we could work at 5.6K and save the 8K for a few specific moments that would benefit from the extra resolution. At 5.6K, an average .exr file would have a size of 80 Mb per frame. It made the compositing scripts very heavy, sometimes working with 30 to 40 passes of CG all at 5.6K, but I think it was worth the extra pain."

Since there wasn't any facility to play back 5.6K frames in real time, each shot was split into 2K tiles to be checked with realtime playback on Double Negative's FilmLight system.