Issue link: https://digital.copcomm.com/i/398245
22 CGW S E P T E M B E R . O C T O B E R 2 0 1 4 V I S U A L E F F E C T S CREATURE SIMULATION Creature Supervisor James Jacobs moved from New Zea- land back to his home country to develop a system at Meth- od that would help make the Grievers believable. "It's an elastic body simula- tor," Jacobs says, noting that it's based on a kind of physics solving known as nite- element analysis, which has been a generic approach to simulations since the 1950s. At Weta Digital, he, Simon Clutterbuck, and Richard Dorling had received a Scien- ti c and Engineering Award in 2013 for Weta's so ware system called "Tissue," a physically based character simulation framework. Jacobs also received a VES nomina- tion that year for his work on the Goblin King in The Hobbit. Originally from Toronto, Jacobs moved his family back and forth between North America and New Zealand while he worked on Avatar at Weta, then Thor at Digital Do- main, and then again at Weta for Tintin. "When I went back to Weta, my wife and kids stayed here, so when the opportunity at Method in Vancouver pre- sented itself, I took it," Jacobs says. "Also, I wanted to do something at a higher level." Once he arrived in Vancou- ver, Jacobs began looking for people who could help him develop a new creature sim- ulation system. "I'm a visual e ects guy, not a hardcore so ware developer," he says. "I needed someone who could implement a core so - ware library. We needed to get something into produc- tion quickly." Jacobs found John Lloyd at the University of British Columbia, who had written a biomechanics simulator in the Electrical Engineering department for speech pa- thology. Lloyd wrote the core so ware library; Jacobs wrote the Autodesk Maya plug-ins. The result is a nite-ele- ment simulation using invert- ible elastic elements. "The linear elastic bit provides an approximation of a material," Jacobs says. "It's good to describe materials that don't undergo massive transformation, so the model works well for visual e ects. It's a simple material model, easy to get your head around. The invertible part makes it more robust." Jacobs explains that before this method was available, when a tetrahedron – the pyr- amid-shaped bit of geometry used in meshes – is inverted, the solver, that is, the simu- lation engine, doesn't know how to deal with mesh, so the volume described by the mesh becomes corrupt. "If the top of that pyramid shape gets squished into a at plane, or becomes at, the volume becomes negative or attened," Jacobs says. "Take a character's arm. If you have tetrahedra in a certain size and the arm moves fast, it might invert. In older approaches, when elements deform in a linear elastic fashion and the movement is more than a certain amount, the element – the arm – could become degenerate. Our solv- er allows things to become inverted and correct them- THE FEARSOME GRIEVER HAS A SLUG-LIKE BODY AND MECHANICAL LIMBS.