Double Negative reproduced St. Peter's Square using proprietary photogrammetry software and satellite imagery © 2009 Columbia Pictures Industries, Inc. All Rights Reserved. Courtesy of Double Negative.

"It was Da Vinci Code on steroids," laughs Angus Bickerton, the overall visual effects supervisor of the follow-up, Angels & Demons (from Columbia Pictures), which pits Tom Hanks' professor Robert Langdon against the murderous Illuminatti, an ancient society that is preparing a large-scale disaster.

The script called for several key sequences to take place in Rome, in churches or cathedrals that the Roman Catholic Church denied the filmmakers access to shoot in. Thus, it was thus no easy task to gather photographic references of the various locations. The teams had literally to pose as tourists and shoot as many photographs as they could in the most genuine way. Clearly not the best process when one plans to rebuild the locations via photogrammetry…

The first artist to defy the Roman Catholic authorities was VFX DP Stefan Lange, who gathered a huge library of stills for the preproduction team to work with. "We used these as a resource -- creating QTVRs that could be virtually navigated -- for screenwriter Akiva Goldsman," Bickerton says. "We had less than six months to deliver an estimated 800 shot vfx count. VFX Producer Barrie Hemsley was the genius who shepherded the tallies and budget with consummate ease. We started working on shots immediately, even though this might mean some of these shots may ultimately be cut. It's always hard to tell a creative artist that their endeavors have just been excised from the film, but the benefit is that creative dialogue about sequences can start from day one of post. I think it's invaluable to block in vfx as soon as possible to help the editing process, and we had the whole film temp composited by an in-house unit two months into post. In the end, we worked on 1157 shots, but only 917 are in the final cut: DNEG did 359 shots, CIS Vancouver 240 shots, MPC 201 shots, The Senate 196 shots and our four-man in-house unit 161 shots."

One of the major concerns was how the team would track handheld shots as the cameras moved through the many crowd shots, often meaning that markers on greenscreens were completely hidden. In the process of investigating potential systems for on set mix and overlay of low-resolution set extensions, 2D3's system set up by for Sweeney Todd was reviewed. It used a small scientific analysis camera mounted on an arm above the camera. Coded markers were posted on the green screen and an initial survey using a digital stills camera was tracked in Boujou to establish positions. A realtime PC system connected to the camera then tracked the markers in realtime.

Bickerton found that the only disadvantage of the system was that a desktop PC had to be cabled to the camera, which didn't fit with [Director] Ron Howard's shooting style. "The new breed of AVCHD mini camcorders were the solution. Nine Canon HF10 cameras recording a very compressed 1920x1080 24P were purchased, along with Sony wide angle adaptors. They were then mounted on top of each 35 mm camera and Double Negative devised a marker system on the slates that would allow the HD camera's offset to be calculated. Whenever a longer lens was used or markers were hidden by foreground crowd, the HD cameras were used for tracking."

For lighting, it was decided to use RenderMan's point cloud baking tools to bake all the illumination into a series of point clouds. Courtesy of Double Negative.

Recreating an Architectural Wonder
Production Designer Allan Cameron built sections of St. Peter's Square and the Basilica at Hollywood Park, but due the massive size of the location, the sets were built at a smaller scale. "This meant that Double Negative had to build two Piazza environments, one was actual size for full background replacements and the other matched to our hybrid set," Bickerton notes.

Led by Visual Effects Supervisor Ryan Cook, VFX Producer Fay McConkey, CG Supervisor Graham Jack and 2D Supervisor Victor Wade, the team at Double Negative set out to reproduce the famed St. Peter's Square. Since LIDAR scanning of the set was impossible, the layout and dimensions of the location were created using proprietary photogrammetry software and satellite imagery. "St Peter's Square created new challenges compared to our previous environment work where we mostly had skyscrapers and office blocks," recalls Cook, "The Vatican is almost entirely intricate buildings, statues and delicate detailing. Because it was a daytime build, it was also particularly unforgiving. In additions, hundreds of props were modeled that could be used whenever required, such as dustbins, souvenir stands, flags, etc."

The lighting created a major challenge as the location was lit by a very complex lighting environment. After the team had added everything in, there were several hundred light sources in the scene, which, even when they had optimized, meant the shadow generation was taking far too long to calculate. It was decided, therefore, to use RenderMan's point cloud baking tools to bake all the illumination into a series of point clouds. Using additional proprietary tools, the team was able to combine all the point clouds for the different groups of lights together, so that they had one point cloud for each region. By splitting up the lighting in this way, they were able to use memory intensive techniques like ray tracing to get the best possible quality in the lighting.

They were also able to use the tools that Pixar had added to calculate ambient occlusion and color bleeding from the point clouds. These were then combined together in the renders, but could be overridden if the lighting had to change. Baking the lighting in meant that the lighting artists could build their scene, hit render, and immediately have a decent starting point for realistic lighting. It also allowed the team to do global illumination effects and produce light bouncing from building to building. "Without the baking technique, the complexity of the models would have been way beyond what we could have managed," adds Jack.