Issue link: https://digital.copcomm.com/i/225858
SIMULATION CG geometry. Every time Elsa freezes a surface, it's 2D artwork that we took into [Side Effects] Houdini and made ice with it. We had to show who she is at different times of her life, when she is happy, sad, angry. She creates mini-weather systems from her being. We didn't want snow shooting out of her hands. " In one sequence, for example, a panicky Elsa backs up against a water fountain. When she touches it, a frost pattern shoots across the edge, and the water in the fountain freezes. "The effects artists previs'd the whole thing in 2D, Mayeda says. "When the " effects animators began looking at it, they realized they could grow it procedurally with particles, but the growth pattern would be too realistic. So instead, they used the designer-drawn 2D artwork to drive the shape of the frost patterns formed in Houdini and the timing. The timing from the 2D artwork was snappy rather than linear and procedural. We spent a lot of time on this show incorporating hand-drawn artwork. " ■ AT TOP ANIMATORS REFERENCED their pets to give , Sven an appealing personality. At bottom, a fight with a giant snowman is the only scene in which characters move on hard-packed, rather than soft, snow. Emotional Effects point them in directions that might influence the film. " Designer Dan Lund, for example, began drawing 2D snow flurries. "We wanted our snow flurries and gusts to have a lyrical quality, not like someone ran a particle simulation with occasional gusts, Goldberg says. "Dan came up with gor" geous tests in 2D, experimenting with positive and negative shapes. Elsa has a signature snowflake design that shows up during the film. And Dan's snowflakes not only had this design, but his snow flurries formed negative shapes that had her signature design. I don't think we would ever have come across that if someone had just said, 'We need snow flurries.'" Working with Goldberg were Effects Supervisors Marlon West and Dale Mayeda. West's career as an effects artist and supervisor stretches back to Lion King, and includes Mulan, Tarzan, Fantasia 2000, and, more recently, The Princess and the Frog. And, like Goldberg, Giaimo, and Buck, he had worked on Pocahontas. Mayeda has been a 3D animator and effects supervisor on live-action films (Mission to Mars) and Disney Animation CG features (Bolt, Tangled, Chicken Little). Together, they helped bring the 2D design elements into the CG film. "This was a rare film in which effects came into the process early on, West says. "We did a lot of 2D tests to suggest " things Elsa could do with her magic. We did proof-of-concept tests. We had an effects artist embedded in layout who did previs. We put 2D drawings on cards, and character animators acted to some of them. And, we did 2D animation that drove During the testing stage, Michael Kaschalk, a studio leader in the effects group and former effects supervisor on Tangled, played around with the idea of capturing designs that Elsa might generate. "He went to our camera capture stage, which we use for digital scouting and handheld camera work, Gold" berg says, "took a wand, and drew arcs like someone with a sparkler on the Fourth of July. We tracked those arcs in space. So, rather than having someone draw curves on the computer, we got interesting shapes and double, triple, quadruple paths. We used these lyrical shapes as forces in a particle system. We ended up not using many of the results, but they informed the simulation that we used later. " Capturing the wand in space also helped the artists create snow flurries that wrap around Anna when she falls down a cliff and lands in a snowbank. "We had someone sit on the motion-capture stage while we wrapped the wand around and around her, Goldberg explains. "The main path gave us an " overall sense, and then Michael [Kaschalk] played around with aesthetic ideas for smaller tendrils that branch off, working back and forth with the directors and John Lasseter. " Throughout the film, snow supports the storytelling and Elsa's emotions. " the snow is tied to Elsa's mood, so it has All an emotional beat to it – the turbulence as it falls, the angle, " West says. "We ended up with 20 kinds of snow falling in the film. And, all the snowflakes that fall are unique. Our snowflakes follow a path like in nature, with a particle that branches and forms plate-like crystals. Even in Elsa's magic, which has a 12 ■ CGW Novem ber / Dec em ber 2013