Step By Step: Van Helsing
Hybrid” is a word that's used often in this era of mix-and-match visual effects, but it's an especially apt description of Industiral Light + Magic's work in Universal Pictures' Van Helsing. Director Stephen Sommers, who brought some difficult effects assignments to ILM for his two Mummy films, presented an even harder challenge with Van Helsing — to bring several of Universal's famous monsters to life.
Among them were Dracula's flying vampire brides, which had live-action heads on CG bodies. Because these brides often flew close to the camera and delivered lines, the marriage of elements had to be seamless. This was especially tricky to achieve in a scene where the brides attack a village, diving down and snatching victims from the ground. Sommers wanted to shift dramatically between the brides themselves and their aerial POVs. In shooting the village plate photography, DP Allen Daviau employed a Cablecam rig high above the full-scale set and — using a remotely operated camera — had captured very dynamic aerial shots. ILM's task was to create CG and live brides that would inter-cut convincingly with the dynamism of those shots.
ILM CG supervisor Doug Smythe brought some experience to the “hybrid character” challenge, having previously won an Oscar for the digital “twisted head” in Death Becomes Her. But in Van Helsing, he says, “The motion of these characters is much more complex than anything we've done before. We had to modernize our approach.”
That entailed doing successive versions of increasingly detailed animations. The process began with video game-quality animatics done at Sommers' production company. “Those were used to plan the sequence, and generally guided the shooting of the background plates,” Smythe recalls. “Once the plates were shot, ILM blocked out animation using a new proprietary system called Poseur. This animation didn't have facial expressions or hair simulation but it used high-res geometry and full textures with all the seaming done. It was good enough to check the continuity of the action. We also did some CG lighting to get continuity of lighting direction.”
ILM's matchmove department had the task of reconstructing Daviau's camerawork. “We used our MARS camera motion recovery software rather than trying to get any actual camera position information from the camera rig itself,” Smythe explains. The approach essentially involved creating a low-res reconstruction of the village. Because ILM had measured the relative placement of all the buildings on the set, they could recreate the village in 3D virtual space.
Armed with Sommers' rough cut of the sequence, the ILM team approached the bluescreen shoot of the actresses with a new idea in mind — they would do motion capture of the actresses on the flying rigs while they filmed the performances. “I don't think that's been done before,” says Smythe.
What made this possible was ILM's new infrared mo-cap suit. “On each actress' suit we had over 40 of the brightest infrared LEDs we could find,” Smythe explains. “The light source had to be infrared so it wouldn't light up the actresses' makeup and hair.” These battery-powered markers would flash for the Vicon motion-capture system and be undetected by other cameras. “The lighting on any stage is going to have a strong infrared component. So these suits couldn't be overly reflective in the infrared band of the spectrum,” he says.
ILM's method allowed Daviau to light the bluescreen as he pleased. And Sommers got two essential elements at the same time — the acting performances that he wanted, and the mo-cap data that ILM would need to animate the CG bodies on which the actresses' heads would be placed. Assisting everyone in this process was a videotape that showed a live composite of the actresses over ILM's previz animation.
“We had a pretty clear idea of how it could be,” says Smythe. “But when you're shooting actresses on wires, they won't be able to get exactly the performances of your CG characters. We later re-did our animation to fit the actual live performances.” The ILM team placed side-view witness cameras on the bluescreen stage, so that when the mo-cap data was processed they could view everything from the camera view and side views to double check accuracy.
The final animation of the flying bodies was done in Softimage, and the vibrating wings were simulated in ILM's proprietary software Cari. The live-action heads meshed well with the CG bodies because they'd been filmed along with the mo-cap. Most of the actresses' swirling hair was live-action, blown about by fans on the bluescreen stage.
In cases where CG hair was added, ILM used new simulation software developed on this show. “The brides have long, curly hair, and during a typical simulation, CG hair often loses its curl,” Smythe says. “We came up with an approach that allows us to simulate the general motion of the hair and keep the micro-motion of the curls as a separate piece of information. Curls follow the motion of the general shape of the hair, but keeps the horror movie ‘bride hair’ that you'd expect to see.”
Rendering was done with the latest versions of RenderMan and Mental Ray, to take advantage of the latest ray-tracing capabilities. As fantastical as these flying brides appear to be, they do have human faces and audiences expect them to exhibit believable motion. “Audiences are more sophisticated now,” Smythe says. “We had to pay attention to the interaction between the CG and live-action parts. By taking pieces of mo cap, modifying that with keyframe animation, and having certain things dynamically simulated, we could fit the pieces together into something that's better than any one would have been by itself. That's the fun of having a well-stocked toy box!”
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