Computer Graphics World

May/June 2014

Issue link:

Contents of this Issue


Page 9 of 35

VISUAL EFFECTS 8 ■ CGW M ay / Ju n e 2 014 poses. But he wasn't just hitting those poses gratuitously. He doesn't just show off. There's a reason behind each pose, which is dictated by the action, and each naturally flows into the next." To help animate Spider-Man in an extreme, purposeful, and yet natural way, the team considered how physics in the real world would affect the superhero's moves. "I call Dave Schaub 'Dr. Physics,'" Chen says. "Physics was very important in the way he directed his animators." In fact, to bring animators up to speed on the principles, Schaub teaches a "Physics for Animators" class at Image- works that is geared toward the challenges animators face. But how does physics apply to a superhero? "We ask, 'OK, what is Spider-Man's superhero ability?'" Schaub says. "The answer is that he can swing through the city using his web without being torn to shreds by the g-forces. That's his superhero ability. But, it doesn't mean he can break every other law of nature. There are also specific rules that apply to the natural accelerations while swinging. If he releases the web, he isn't flying. He's falling, and gravity should impose its natural effect. When he plummets, he holds out until the last second – that's his finesse – and catches the web at a nice moment. Sometimes when he does that, he gets whiplash and it looks like it hurts." As is typical for live-action films, Imageworks animators started with previs supplied by the production unit that described the basic action from a particular camera view for the shots. "Sometimes Marc [Webb] was sold on the previs and wanted to use it as a gold standard," Schaub says. "In other cases, it was a starting point. We were always trying to find different methods for Spider-Man's swinging." They labeled one new method the "overhand scramble." "The path of Spider-Man's swing is a pendulum," Schaub says. "His arc swings into a trough before he swings back up. So, to keep him continually moving upward, he goes hand over hand up the web. That gives him the ability to accelerate upward, which is important in a chase scene." To nail a good virtual camera angle for the all-CG shots, the crew often used a similar system to the one they devised for the animated feature Surf's Up. "Once the layout was approved, we used a [real] handheld camera with a camera operator behind it to frame the shots," Schaub explains. "It's like putting a camera operator into the CG scene." The animators captured a more casual filmmaking technique from the real world, as well: They would sometimes strap a virtual camera to Spider-Man's torso. "It was like the GoPro shots you see on YouTube," Schaub says. In-house tools helped the animators by checking the integ- rity of the animation according to the laws of physics. Techni- cal Animation Supervisor Dan Sheerin explains: "Every time Spider-Man leaps from a rooftop or transitions from swing to swing, gravity takes over and we have to remember Spidey is falling, not flying. Our tools make sure his acceleration is accurate. They work out the forces that exist, like gravity, and calculate the motion that would result." With the proprietary jump tool, for example, the height, du- ration, and path of a character traveling through the air changes as an animator adjusts the anticipation phase. The tools even apply physically correct motion to the character's muscles. "Our muscle system reverse engineers the forces acting on a character's body mass given the overall animation At The Moving Picture Company, a crew of approximately 170 worked on 350 shots for The Amazing Spider-Man 2. Artists in London and Bangalore supported the work done mainly in Vancouver. The shots included a sequence in which Max (Jamie Foxx) becomes Electro after falling into a tank filled with electric eels, another that follows Peter Parker's girlfriend Gwen's 90-story ride inside a glass elevator, sent planes through volumetric clouds, and created a digital Manhattan in several shots. The filmmakers shot Foxx on set "dry for wet." MPC artists added the water, approximately 30 eels in various sizes, and the electrical effects. "We cyber-scanned Jamie Foxx and rigged him for roto animation for the whole sequence," says Pete Dionne, digital effects supervisor. "So, we had the luxury of creating specific interactions with the eels wrap- ping around his appendages and his head. It was all hand- animated; the blocking was very specific." Inspired by the Electro skin effects created at Image- works, CG Supervisor Stephane Paris designed a shader- based bioluminescence quality for the eels in Pixar's Ren- derMan. Compositors working in The Foundry's Nuke drove the timing and position of electrical flashes and shimmer using maps. "As the eels wrap around Max, they started flashing and arcing electricity," Dionne says. "The more excited they got, the more we exaggerated the electricity on their bodies, the subsurface electricity, and the flashing in the eels." The arcs of electricity from the eels to Max were particle- based simulations with a fluid-based plasma effect layered over time. For the water effects within the tank and at the climax when the tank explodes, the crew used Scanline's Flowline fluid-simulation software. "They filmed a practical explosion, but for the most part, we only used it as reference," Dionne says. "Our explosion dwarfed the practical elements and made them difficult to integrate." –Barbara Robertson Electric Eels ARTICLE: Go to "Extras" in the May/June 2014 issue box for more on MPC's work .com .com

Articles in this issue

Archives of this issue

view archives of Computer Graphics World - May/June 2014