Issue: Volume: 25 Issue: 8 (August 2002)

Blowin' in the Wind




Animators bring down the house in a television commercial for VISA

By Karen Moltenbrey

Like the fairy tale characters on which they are based, the three little pigs in PDI/DreamWorks' recent television commercial discover-albeit the hard way-that building a house of straw is not a structurally sound decision. In the whimsical all-computer-generated spot for Visa, which is airing in Latin America, the pigs become wiser as they build houses of straw and then stick, which are blown to the ground by a huffing, puffing wolf. Finally, the trio builds a house of brick, purchased with a VISA card.

Ironically, constructing-and decimating-the 3D model of the straw house proved to be more of a technical feat than creating the house made of bricks. "The straw house had to look realistic," says director Cliff Boule, "and giving the straw the right look and weight when it was blown down by the wolf was extremely difficult to accomplish."

With such an oft-told tale, it was important that we create a unique, new look," says Laura Lockwood, a producer for the PDI Commercial Division. To that end, the group created distinctive-looking characters, props, and lush environments using PDI's proprietary tools and technology that had evolved from the feature film Shrek. For the complicated straw-house effects, though, the team used a commercial software product: Alias|Wavefront's Maya.
To create the stars of a commercial featuring the three little pigs, PDI's Commercial Division used proprietary tools and technologies based on those PDI had developed for the feature film Shrek.




Initially, effects animator Randy Hammond constructed the straw house with closed-volume shapes that resembled crudely crafted bricks, which he stacked and layered to form the outline for the house. He then filled each closed-volume "brick" with particles, generated with PDI's proprietary software. "I created a data file that told me where each brick was oriented and positioned in space, and used that list to fill the bricks with particles," he explains. "Then, when I viewed the entire data set, it looked like a house made entirely of particles." In all, Hammond generated more than 180,000 particles for the desired effect.

Hammond im ported the so-called particle house into Maya, where he created the "explosion" simulation. First, he wrote an extensive particle expression in Maya to control the fine detailed motion in the particle animation, then added small vortex fields to achieve swirling eddies and the overall blowing motion. He then imported all the particle sets on a per-frame basis back into the proprietary animation software, with which he generated NURBS-based curves for each particle, "so in the final animation, the little pieces of straw would bend and rotate in the wind, rather than remain static."

Hammond then generated geometry along each of the NURBS curves within PDI's proprietary rendering software. Next, he applied PDI's hair shader tool-which is optimized for very thin geometry-to each curve, so when the curves were rendered, they resembled extremely thin tubes. "That gave us the straw appearance we were looking for."
Maya-based particle animations helped create the impression that the house of straw was being blown down. Vortex fields were added to the particles to make the pieces of straw swirl appropriately as the wolf huffed and puffed.




Despite the complex construction of the straw house, the wolf in the commercial-with just a huff and a puff-blew it down with the greatest of ease. Alas, it does not appear that the sturdy house of bricks fared any better in the commercial rendition of the story, as the wolf is shown in the last shot purchasing a bulldozer with his own Visa card. So much for fairy tale endings.




Key Tool: Maya, Alias|Wavefront (www.aliaswavefront.com) infoNOW 84

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