Computer Graphics World

March / April 2015

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22 cgw m a r c h . a p r i l 2 0 1 5 that would be a damage state that would pull the correct textures for the shot." The Scouts were identical; however, they, too, had wear and tear. "We mainly changed their numbers and textures," Poon says. In 450 of the shots, Chappie, which has become part of a gang, wears gold chains made of 5,000 individual links, each depending on a full rigid-body simulation to bounce and jiggle as Chappie moves. "The chains interact with one another, and people interact with the chains," Harvey says. "And that was only a tiny aspect of Chappie. It was a massive undertaking." The effects team pre-set the simulations in Side Effects' Houdini so that a first pass from animation could run automat- ically. Aer shot review, the effects artists could tweak the simulation as necessary. "It was a slick process," Poon says. "The chains had default settings, so the animators would run a pre-roll on the animation to go from static to the first frame, and then the chain simulation would run. The cool part was that the effects artists didn't have to get involved until the first anima- tion pass was done. It was a big investment up front to set up the system, but it was successful." The effects team also sim- ulated the hoses hanging off Moose, but Chappie's hoses moved via the rigging system. R O B O T S O N S E T During filming, Copley per- formed Chappie. A stunt actor played Chappie when he was still a Scout and performed Copley's stunts. And other stunt actors played the stiffer, more robotic Scouts. "Sharlto [Copley] played Chappie loose," Harvey says. For the more tank-like robot Moose, a member of the Image Engine crew walked around with a tennis ball on a pole. "We intended to have him in the shots only for rehearsals," Harvey says. "But, the actors wanted him in the shots. So we had to paint our own guy out of the shots. We tried to be as smart as we could. We didn't start roto paint until we had the first pass of animation. That way we could paint away only the part that needed to be removed." Although Copley and the stunt actors were on set, the crew decided not to motion- capture them. "We did a lot of tests and decided we could better spend the money elsewhere," Harvey says. "If we had 10 or 30 characters in a scene, it would have been prohibitive to animate them by hand, but we had one main character. The amount of time needed to clean up motion-capture data isn't that much different than animating by hand, so there was no efficiency gain in terms of money. We could do the an- imation by hand as easily. And, the visual effects crew on set could be more streamlined and less intrusive. We didn't have to calibrate an array of cameras; we didn't slow anyone down. Neill shoots very, very fast." Copley wore a gray suit on set, but that was for lighting reference, not motion capture. Rather than motion capture, animators did rotomation. "We had him in the back plate, and animators animated on top by hand to mimic his CHAPPIE HAD 16 STAGES AND 12 SUB-STAGES OF DAMAGE AND DESTRUCTION.

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