Computer Graphics World

March/April 2013

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n n n n CG Characters (Top) A new volumetric tool kit helped artists at MPC create clouds behind their digital beanstalk. (Bottom) Modelers and animators used the same rig to build the beanstalk section by section and control the movement. effects supervisor] and Matt Welford [on-set supervisor] in Vancouver." Modelers at MPC matched and extended a 30-foot-tall practical set that had 12 pieces on moveable bases. "One of the challenges was to design, build, animate, and render a model that shoots upward through the farmhouse into the sky," Butler says. "On any given shot, it could be a mile high." The animators would need to move the pieces to grow the enormous plant and, later, to give it life. So, modelers and riggers worked together to design and build sections that could fit together and a rig that could connect the pieces, "like boxcars," Butler says. "We could define a master curve and populate it with beanstalk assets, leaves, and connecting vines. We based the modeling tool kit on an animation rig. The modelers would pose curves, convert the curves to geometry, then freeze and lock them. At first, this seemed like overkill when it came to modeling, but the animators needed to move pieces around and the modelers could go into a scene and use the rig to tweak the model. We kept it live the whole time." Lead Rigger Devon Mussato designed the system. Head of Modeling Chris Uyede worked with Lead Modeler Ryan Lim and 28 his team, and with Animation Lead Jeremy Mesana, to define the sections and determine how they would fit and how the rig would read them in. Texture Lead Erik Gronfeldt did look development. "And finally, when we got it up and running and found out how heavy it was, Mark Williams, our lead R&D technical director, wrote a system that broke it into pieces so animators could work with lightweight scenes," Butler says. "We had outsmarted ourselves. As the beanstalk grew, our problems grew, and we had to find our way out. By the end of the movie, we had a good system. It was definitely a technical evolution." One way in which they had outsmarted themselves was by treating the beanstalk as a creature. Even though it was organic, they realized only later that some techniques used for hard-surface modeling might have been more efficient. "We're so used to doing creatures, where skinning involves hand painting," Butler says. "The complexity of the beanstalk, though, came from design and shading. We realized too late that we could do all the skinning at runtime because it was just defining how the geometry follows a joint. With robots and hard-surface models, we have always done that in the renderer to save calculations. We had thought of the beanstalk as a flexible object with stretching and twisting, when so much of the time it was more like a hard-surface model." However, the process the team went through to create the beanstalk led to an important discovery. "We realized we needed to work with R&D earlier, especially given the high complexity of projects," Butler says. "R&D can abstract and find ways to accelerate parts of the process. The partnership we formed has led to an ongoing collaboration." Jack also marked the studio's first use of a new volumetric tool kit developed during the past few years. "We used it for clouds," Butler says. "Particularly when the camera looks off into the cloud shape. "We would model simple geometry to lay out the size and overall shape, and then we layered algorithms onto it to give it edges. Whether it was fat and puffy or small and stretched out, we could describe the clouds through procedural operations and have full volumetric clouds. We started off experimenting, and by the end of the show, we had the render times down. We have a great relationship with Pixar, and every couple months we get further into the new features they're adding to RenderMan, integrating more of our effects technology into it." Even though Digital Domain rendered with Arnold and MPC with RenderMan, deep compositing, developed at Weta Digital and implemented in Nuke, made sharing shots easier. "We'd give them approved blocking and a simple beanstalk rig they could pull around and approved blocking," Butler says. "Their giants could interact with and affect the beanstalk. They got approval on the beanstalk and giant animation, and locked that off. And then both sides added only secondary animation. And what saved us in the finishing stage was deep compositing." When MPC delivered renders to Digital Domain or vice versa, the renders came with deep passes. "We'd comp each other's work, and it turned out to be as simple as that sounds," Butler says. "Deep compositing wasn't invented for that reason, but it's been a boon for sharing between facilities." Although it's unlikely we'll see another film with a giant beanstalk and earthy-skinned giants, the techniques and technologies that people in these studios created will likely see their way into future films. Life in visual effects may not be a fairy tale these days, but it is often fantastic. n Barbara Robertson is an award-winning writer and a contributing editor for Computer Graphics World. She can be reached at March/April 2013 CGW0313-Jackpfin.indd 28 3/14/13 12:19 PM

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