Issue link: https://digital.copcomm.com/i/147928
software and extended to manage the multiple species of monsters in this film. Northrup also developed tools within Presto that the layout artists could use to populate the crowds, place them, and see a lightweight representation for the first time. "When you have crowds, they are basically like a set piece," Bakshi says. "The goal was to have the layout shot composition persist through the pipeline. When these procedural characters got too close to camera or needed to react to something specific, we could parse them into a project for hero crowd animation. But, we always strived to use as much of the crowd animation as we could. Seeing the crowds and having them consistent at every stage in the pipeline really helped Dan [Scanlon] and the creative leads." Ubiquitous Simulation All those characters – some furry, some with costumes – presented simulation challenges, as well. "We have simulation in 89 percent of the shots," says Christine Waggoner, simulation supervisor. "Simulation is now ubiquitous. We had hair, cloth, grass, trees, ropes, paper, books, stuffed animals, newspapers, banners, bushes, backpacks, zipper tabs on backpacks, keychain on a backpack, skateboards, ■ RIGID-BODY dynamics moved the grass underfoot; FizT moved Sully's hair. in 1988 titled "Spacetime Constraints," in which they described animating a Luxo lamp using physics rather than keyframes. Witkin and Baraff began working on cloth simulation at Carnegie Mellon University in 1992, and while there, developed Maya Cloth for Alias|Wavefront. All three scientists would join Pixar. At Pixar, Kass developed a cloth-simulation system for Pixar's Oscar-winning short film "Geri's Game" (1997), and that was the launching point for new technology developed by Witkin and Baraff. They began working on the code base for the new simulator in 1998. The result was FizT, which solved a historic problem with cloth intersections. The three scientists received Scientific & Engineering Academy Awards in 2006, and Pixar patented the technology. For Monsters, Inc., FizT managed Boo's T-shirt and the 2,320,413 hairs that covered Sully's purple-spotted, eight-foot-tall body. The slimmer, younger Sully now has 5.5 million hairs. The latest evolution of FizT, now upgraded and implemented within Presto, handled the dynamics for hair and cloth for Monsters University, as it has in every film since Monsters, Inc. except Brave. "We didn't have the problem with curly hair that they had in Brave, so we chose to use FizT for hair and cloth," says Waggoner. "It simplifies the pipeline and it made sense from a legacy standpoint to have the continuity of technology." Because the characters didn't wear the long, flowing garments that Merida and her mother wore in Brave, it wasn't as necessary for animators and simulation artists to work together on this film. Typically, the simulation artists for Monsters University would run the dynamics on characters already animated. New to this film, though, was a representation of a character's hair rendered in hardware. "Animators on the original film could only see Sullivan's skin," Waggoner says. "But the composition looks different when you have voluminous hair. So, we collaborated with the animation department to give Sullivan a GPU groom." Under Foot Frisbees. We had lots of beds in the movie, so we simulated the blankets, sheets, and pillows, and helped Sullivan lift a mattress to get to a dog. We even simulated Mike's hat a little bit." An effects team created water, fire, explosions and other largely particle-based simulations with Side Effects Software's Houdini. For the simulations relating to characters and objects, Waggoner led a small team of eight simulation artists who used the studio's proprietary software. Pixar scientists developed the studio's first version of a hair and cloth system for Monsters, Inc. (see "Monster Mash," October 2001). The simulator, dubbed FizT for cartoon physics, grew through collaboration among three senior scientists at Pixar: Michael Kass, the late Andrew Witkin, and David Baraff. While at Schlumberger Research, Kass and Witkin had published a landmark SIGGRAPH paper One of the more innovative techniques developed for Monsters University, according to Waggoner, was a vegetation-simulation system that managed the dynamics when hundreds of students trample the grass in the campus lawns. The proprietary system uses the opensource ODE engine within the pipeline for the rigid-body simulations. "We created a technique that deforms the grass at render time," Waggoner says. "We didn't do a traditional curve simulation that you might think we would do because of the vast amount. To write out caches for that amount of data would be too heavy. So, we feed it in using a rigid-body simulation that drives a deformation at render time. It was a relatively innovative idea." The simulation artists start with a grass model created in the sets department, and specially rigged characters. "The grass model is a procedural system that renders curves that represent the grass," CG W July / August 2013 ■ 15