Computer Graphics World

August 2009 15 Visual Effects n n n n as the studio has done in the past, for this scene the artists had to reproduce the set, as well. "We remodeled the entire room from two camera views," Robinson says. "We re built the tables, cups, plates … everything in 3D using digital stills for textures." After consulting with Jose Granell, Cine site's model unit supervisor, the team de cided to create 100 different explosion events as the detonation moves down the great hall, to mimic how Granell would rig a series of practical explosions to create a dense effect. "We staggered the explosions and previs'd it with Tim Burke to get the timing," Middle ton says. For the sequential explosions, Voss used Blast Code software to shatter the stained glass, animate the plates moving off the tables, smash the cups, and manage the interaction with the environment. " e dynamics were rigidbody simula tions with Blast Code," Middleton says, "but with Holger [Voss's] careful choreog raphy." Lastly, Robinson's team compos ited dust and debris passes rendered with Pixar's RenderMan into the explosion us ing Apple's Shake. MPC: Quidditch Now that the contestants are teenagers, Yates and Burke wanted to give the Quid ditch matches a little edge. "Even though it's still kids on magical brooms, we tried to make the sport more of a sport," says Nicolas Aithadi, visual effects supervisor at MPC. "We decided to create more credi bility by giving the camera more of a televi sion feel. So, we looked at everything hav ing to do with aerial shows and Formula 1 races." ey created the broadcastsports feeling and dynamism they wanted by us ing the virtual equivalent of 500mm lenses to flatten the perspective and by having the cameras catch up with the action. During Half-Blood Prince, we see a try out and a final match. For both, although the crew shot the actors on wires on a bluescreen stage, in 90 percent of the final shots, the competitors are CG. "We want ed something more controllable than what we could shoot on set," Aithadi says, "and more extreme." Knowing the digital athletes would be close to camera, MPC decided to use video grammetry to create the photoreal charac ters. "It's like photogrammetry, but with moving images," Aithadi says. To capture the moving image, they positioned four cameras around an actor wearing 80 track ing markers on his or her face and sitting in a chair. Two cameras were in front, high a nd low, and two were at 45degree angles on each side. "e idea was to use that data to animate the CG face, and at the same time, acquire the textures," Aithadi says. "We'd have mov ing geometry and moving textures, and the texture would match the geometry exactly." e first test took a week and a half and had promising enough results that the crew decided to go ahead and capture all Mystery Train During a particular shot, created with help from The Moving Picture Company (MPC), the camera focuses on students Ginny, Luna, and Dean Thomas, who are riding in a train. The camera pulls out of the window, a dining car rolls past, and then, the camera goes inside the window of a third car to focus on Harry, Ron, and Hermione. But there was no train—only the in- side of one train car on set, configured and then reconfigured to simulate the three train cars, and filmed with a mo- tion-control camera. MPC created the rest and put the jigsaw puzzle together. "It was insane," says Nicolas Aithadi, visual effects supervisor. "We had one person working on the shot for six months, creating everything that didn't exist on set—the train walls, the track, everything outside the windows—dealing with all the motion-control elements, and keeping all the motion-control and CG ele- ments in sync. At one point, I thought, 'Enough already. We'll do it all in 3D. I'll pay for it.' But, it would have been a long process in 3D as well, and the real characters help sell the shot. It has a nice feel to it, and the way it fits into the story is quite cool." –BR MPC created a digital stadium for the extreme Quidditch sport and used videogrammetry to put real faces on digital athletes that star in 90 percent of the shots.

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