Issue link: https://digital.copcomm.com/i/225858
GROOMING ■ Artists at Reel FX devised a feathering system, called Avian, for Reggie, Jake, and the rest of the flock. department rigged and controlled. "We placed them all over the body and the feathers would interpolate the differently shaped surfaces, " says Pitts. "Avian is unique in that it is not an instancing system. It's more that each shape is interpolated to get the final feather shape. " In most bird movies, like Rio, the feathers look more like fur, and it's hard to see the O shapes. In these instances, the artists use little fly-outs here and there to give the illusion of feathers. But for Free Birds, the art required the feathers to be distinct, like little shingles. "The problem with distinct feathers is that you see the penetration a lot easier, says Pitts. " Indeed, the artists had to contend with the constant colliding and stretching whenever the turkeys moved. Initially, they devised a plan that involved solving for a simulation, but after a long, painful process, they changed directions and instead of trying to fix the problem, developed a system that would prevent the colliding in the first place. Called Aim Mesh, the solution essentially placed a polygon cage over the Avian feather system to drive the orientation of the feathers. Animation would then rig up the Aim Mesh so when there was squashing of the body, such as when a turkey lifted its leg, rather than have penetration, custom deformers on the Aim Mesh would simply pull up the mesh. "It prevented 99 percent of our collision right off the bat; the remaining 1 percent that was colliding was barely visible, so we just let that go, says Pitts. " The crew exported all the feathers to an Alembic format read by a Pixar RenderMan procedural, which converted the information into RI curves for rendering. A shader, developed by Marlin Rowley, enabled the group to pull surface information from polygon representations of the feathers – a smooth normal from the polygon mesh – and apply that to the barbs of the feathers for smooth shading across the entire feather. Grasping the Concept In Free Birds, the turkeys often use their wings as hands, so the feathers had to act sort of like fingers. "If you look at all the animated movies that have been made with birds in them, the characters either have wings that aren't really used as hands, or they have hands that are not wings. We have characters whose wings are used as hands, so the challenge with that 42 ■ CGW Novem ber / Dec em ber 2013 .com ARTICLE: Go to "Extras" in the November/December 2013 issue box for an article on the film's production. was getting enough strength out of the fingers, even though they were made of just feathers, Pitts explains. " With help from Tom Jordan, modeling supervisor, the crew devised a feather-stacking solution, as bunches of feathers were stacked atop one another, with the thickness controlled by animation. So, in scenes where they needed strength out of the fingers, the group would bump up the number of stacks and the thickness, but in scenes where the fingers needed to be feathers, they would turn the system way down and it would look like all the other flight feathers on the turkeys. "The animators needed the freedom to make the birds do whatever they wanted because sometimes they were doing bird things and other times human things, and the system had to support both, says Pitts. " On average, there are 11 turkeys per shot in the film, although some scenes had upward of 50 feathered characters. In one scene, 1,241 turkeys are visible. To keep rendering manageable, the crew employed some tricks to help cut back on the data crunching – for instance, some of the background birds had rendered polygon representations of feathers rather than actual feathers. Nevertheless, there were usually millions of feathers on the screen at any one time: Reggie alone has 6.2 million hairs, or barbs, while Jake sports 2.2 million, which translates into 5,086 feathers – slightly more than a real turkey, which averages 3,500 feathers. But, real turkeys can't trot the line between human and avian behavior, nor can they change history as Reggie and Jake attempt to do. And, perhaps best of all, real turkeys don't have the personality to pull off a starring role in a comical, time-traveling animated feature film that's a visual feast for audiences – particularly vegetarians. ■ CGW Karen Moltenbrey is the chief editor of CGW.