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Ron's Empire

May 15, 2009 12:00 PM, By Michael Goldman

Ron Howard builds his own Vatican.

Explosion

While CIS handled much of the environmental work among the close to 1,000 digital-effects shots in the movie, Bickerton involved three other facilities in the project, with several crucial sequences going to Double Negative in London. London's Moving Picture Company and The Senate were the other two facilities involved.

All the wide shots of Saint Peter's Square in the movie, plus the crucial antimatter explosion that takes place in the skies over the square, were handled by Double Negative, and Bickerton says they were some of the movie's most complex shots. The shots required extending a 400'x400' set of the square—which was built at Hollywood Park in Los Angeles—filling it with digital crowds, and then having the crowds and architecture react to a massive explosion that takes place in a helicopter over the square.

"It's an explosion in which matter and antimatter collide and create a huge event in the sky," Bickerton says. "We started with the idea that it would look nuclear, and we studied DVDs of early nuclear explosions. But Ron Howard said he wasn't sure that was the way to go. He suggested we go more in the direction of a supernova, as we've seen from images through the Hubble telescope. [Double Negative] did tests for us to simulate clouds being blasted apart and this idea of expanding matter, and as the matter expands, a shockwave parts the clouds and also hits the assembled throng on the ground [in Saint Peter's Square], throwing them around like dolls. And then you see the atmosphere charged up and the blast creating an aurora across the skies."

Much of this effect was created in CG at Double Negative, but in addition to those elements, other lighting elements were created practically on set at Hollywood Park. For the bright light from the explosion that illuminates the square, filmmakers used old carbon lights on rods, touching the rods together to create a unique light flash.

"We wanted to do a little bit of the explosion light in camera," Totino says. "It's the way Hollywood used to create lightning effects, where you create a little electrical short and hold a huge spark in place. Modern lights create lightning that is quick and does not have a lasting effect, so we tested carbon scissor arc lights. With the right safety precautions, we achieved that Frankenstein-type lighting."

The explosion also required sophisticated crowd work as people in the packed square interact in response to the blast's energy wave. Bickerton says typical crowd movement in the square throughout the film was accomplished using a standard sprite technique (mapping images to controlled, moving particles), but when crowd members are knocked about during the explosion, Double Negative largely relied on motion capture.

"We used motion capture, along with [Side Effects Software] Houdini to manage the crowd elements," Bickerton says. "This is a combination that they developed internally at Double Negative to give them better control, and it let us more realistically throw people around."

Bickerton spent a great deal of time pondering the best way to obtain tracking information for elements going into visual-effects plates without slowing down production.

"Ron doesn't shoot lock-offs—his camera is always moving," Bickerton says. "So the key thing was to go there prepared as possible for the greenscreens, and that meant looking into a variety of methods to make sure we could track the shots. We mulled over the idea early on of some sort of mix and overlay, meaning some realtime tracking of the camera to preview the overlay of set extensions onto the actual set. The problem with that was that I knew we would be shooting with as many as five cameras at a time. Normally, you would prep the system for the main camera. But we couldn't always dictate which camera would be the 'A' camera, and anyway, Ron and Salvatore wanted to keep turning and shooting as they saw fit and leave some of that decision-making to post."

"So that meant no on-set overlay. However, there were several interesting systems around to get the data in real time for tracking purposes only. We looked into optical motion capture of the camera itself. The downside to that was you have limited volume—you usually need eight or nine cameras to cover a 60'x60' area, and we had a set that was 400'x400' at Hollywood Park. You could never mocap that entire area, and to do it in units, or volumes, would just be too cumbersome.

"We therefore went to a system created by 2d3 [creator of Boujou tracking software) for the film [Sweeney Todd: The Demon Barber of Fleet Street]. That involved mounting a little videocamera on top of the film camera—a 1K-resolution Motion Analysis-type camera. They put barcoded markers on the greenscreen, called 'fiducials.' They then took multiple digital stills of the markers and, using Boujou software, worked out where the markers were by doing a track of those stills. Knowing that information, they can take the live feed from the videocamera and get a realtime track.

"It's an interesting approach, but the downside is you have to be tethered to a desktop PC capturing data and imagery. Therefore, I thought about not doing it live on set—just putting the camera on there, recording the pictures separately, and tracking it later. We did tests that were promising, first with a mini HD handheld camera from Sanyo. We tried mounting it with a bracket on top of the film camera with a wide-angle adapter on it to see if we could possibly track off a wide-angle view on that camera and translate it to the film lens just a few inches below."

Bickerton calls those tests "extremely promising," but before implementing the system, he switched to a then-new Canon Vixia HF10 AVCHD (1920x1080) camcorder, which is capable of shooting 24p.

"That camera was small enough and discreet enough, so we bought nine of them and mounted them on every camera body that might possibly be used in the production," Bickerton says. "We put a wide-angle adapter on it and shot the equivalent of a 22mm lens in terms of field of view. It's fair to say that over 50 percent of the shots were tracked using video from that camera and then transposed to the film camera.

"Double Negative also added a nice slating technique, putting little LED markers on the slate. Whenever we shot a timecode slate, when the clapper clapped the slate, he held it in front of the film lens and then twisted it 45 degrees. From seeing the slate from those two positions—facing the camera and 45 degrees to the camera—we could work out the spatial offset of our little HD camera. That meant we could shoot handheld and our little camera nested on top of the film camera. And because it shot 24p, I didn't have to synchronize the camera up, and knew I could be a half-frame accurate in terms of the video. It's massively compressed HD, of course, but it was shooting wide enough and seeing enough of the set that you could easily get around compression artifacts."

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