Computer Graphics World

March / April 2015

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m a r c h . a p r i l 2 0 1 5 c g w 2 1 not motion-capture Copley for Chappie's performance. B U I L D I N G T H E R O B O T Work on Chappie's body began at Image Engine during the months before production as the crew turned concept art from Weta Workshop into a 3D model of a generic Scout. That digital model would travel to Weta Workshop for printing and assembly into a full-scale, poseable prop that would be occasionally used on set. Although the Scouts – and Chappie before his rebirth – would have robotic motion, Chappie would need to have Copley's full range of motion, and yet be plausible as a robot made of metal. "We knew that Sharlto [Co- pley] would perform Chappie," Harvey says. "It was important that Chappie could move well. So, we spent a huge amount of time on joint articulation. And, every piece had to be manu- factureable." For reference, the crew looked at prostheses, gearbox- es, engines, motorcycles, hard drives, and real robots. "It was important to Neill [Blomkamp] that everything we did was based on something," says Barry Poon, asset manager at Image Engine. "The concept art from Weta Workshop didn't go into fine detail, so we had to work out the internal parts in the 3D model." Five modelers worked in Auto desk's Maya for four months to build the basic, generic Scout model that Weta Workshop would send to 3D printers, that Image Engine would augment to create the damaged Scout which becomes Chappie, and that Image Engine would duplicate to create the 100 police robots in the film. The final model sent to Weta Workshop was made with 2,740 objects. "Realistically, he's more than that," Poon says (see "The Many Parts of Chappie (And Moose)," page 24.) "Our 3D model of the palm of his hand is made of 20 pieces, because of all the mechanics we needed to move the fingers around, but Weta could print fewer. The external case for our hard drive on the [digital] robots would have to come apart, but they could print it as one piece." To print the model, Weta Workshop needed to thicken some of the parts, which they sent back to Image Engine to match. "Anytime the Scouts were inactive, they wanted to film practical assets, so we wanted to match them as closely as possible," Poon says. D A M A G E A N D O T H E R S T A T E S The crew at Image Engine, mean- while, turned the generic sculpt of the Scout into the CG robots that would appear in the film. "You never see the CG version in a pristine state," Poon says. "The robots all needed to look like they were in service for a year or two. When we gave the model to Weta, we included our thoughts on what materials to use per object. They did prints and paints on the practical ro- bot. Then we took photo refer- ence and created our materials to match, but pushed them a little more, trying to follow the practical lead as much as possible. We start with physical- ly accurate materials and then art-direct as needed." Because the CG characters' physical appearances change through the film, the artists cre- ated 16 versions of Chappie and eight of Moose. There is also a third robot in the movie, a spoiler. "We see it in only three shots, but it's really important," Poon says. "It's pristine. It was really important to Neill that the audi- ence knows who it is." The third robot doesn't change during the three shots, but Chappie goes through nu- merous changes in his 1,000. He takes an RPG to the chest, he has graffiti painted on him, he's damaged in other ways, and in some shots he wears chains. "We had one asset for Chap- pie with all the different damage states built in, so it was a lot of work to manage," Poon says. "He had multiple legs, arms, and panels, and we had to track what was damaged, where, and when. We charted it out, but then animators would make a change. At one point, Neill has Chappie splash through a pud- dle. So, it was a lot of work for us to manage. We knew it would be difficult, though." The studio used Shotgun's soware for tracking, and within that tool, they tagged appropriate assets per shot so that lighters, for example, would know which version of Chappie and Moose to use. To help Shotgun and Maya communicate so that Maya would load the correct model and textures, the studio wrote proprietary soware. "Some damage states are driven by geometry and textures at the same time," Poon says. "Some by texture only. If there is blood on Chappie or Moose, THE 5,000 LINKS IN THE CHAINS GANGSTA CHAPPIE WEARS MOVE WITH RIGID-BODY DYNAMICS.

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