Wednesday, December 03, 2008

Bolt: The full background story

Disney's BOLT rolls onto new ground with Rhino character rigging.


Disney’s latest film BOLT, is a product of changes that are not flashes in the pan. With John Lasseter as Chief Creative Officer of Disney Animation as well as Pixar, the Disney culture and even the facility has evolved in some very auspicious ways. Walls were knocked down, figuratively as well as physically. Anything that didn’t hold up the roof was pulled out, and offices were opened to light as well as ideas. Artists were encouraged to explore the boundaries of creativity. And in the case of a hamster in a ball, Rhino, Bolt’s ardent fan, patent pending technology and a Disney animators’ voice-over career was born.

While some painful changes had to be made such as replacing the original director, Chris Sanders, with directors Chris Williams and Byron Howard, the outcome is positive. “Chris Williams and Bryon Howard have this beautiful heart,” said John Lasseter. “These are sweet guys. They are very funny, both of them, but they are very sweet, and we knew that would come out in this film. One of the things that happened on Bolt was the directors and story crew started working as a creative team, like this studio has never seen before. And they really became a tight solid group. They trusted each other, worked together, were very honest to each other, and were dedicated to the same thing.”

John Lasseter:

While Bolt was Disney’s first film to be released in stereoscopic 3D from the outset, introducing several patent pending technologies in painterly effects and rigging, Lasseter sticks to his mantra. “It was all about the story. Our humor comes from the personality of the characters, like Rhino, one of the funniest characters we’ve had. He’s just so honest, and that kind of thing is just so brilliant.”


Rolling through the dappled sunshine is Rhino, the little hamster whose ebullient animation curves rarely ‘flat-lined’. The chubby ball of energy was an intersection nightmare weighted down by too many controls. That was until the animation team redesigned the rig. Currently referred to as PSD’s, (Pose Space Deformers), the corrective shape controllers were based on the distance of the mesh vs. the internal joint rotations. These tools made the animation possible, but they couldn’t have been so successful without the team enthusiasm needed to solve the problem.

(Yes, the images no longer match up with the text)

Initially, Rhino's rigging was like any other character, but as the story and characters evolved the added alterations became unruly. According to Animation Supervisor Clay Kaytic, “the original rig was designed as a quadruped, which worked great. You could run Rhino around all over the place and it looked fantastic. But when you stood him up, you were fighting so much geometry crunching, it was really restrictive from an animation standpoint.

As the character developed and the rig reflected Rhino’s animation requirements, the model grew too heavy to work with efficiently. “We’d say, we need this, we’ll just add more controls. Well, that affects that, well, we’ll add more controls. So by the end of the first version he was so complicated and so heavy, that turning on everything to make him work right, he was soooo slow!” said Kaytic, wincing at the memory. “That is a pitfall of CG. You can keep adding fixes, adding a button, a deformer on top of that, making the model really heavy. The first thing we did was strip things out and reexamine. This was the right effect but how can we do it in a faster way that we can turn on and animate? In the end, he wasn’t that slow. But he was complicated.”

That issue prompted a design rig that ventured into new collaborative but unique working methods for Disney. “We added a second skin, and would blend between the quad pose and the biped pose, so when you stood Rhino up you went to the other skin and it would blend the shape. Or you could even go half way between a quad and a biped model.” Corrective shapes typically are added to isolated areas of the body such as a joint of an elbow, for example.

But with Rhino they tackled zones where corrective shapes were required, but overlapped because Rhino’s joints were so short. “We had to figure out how to base it so it was not so much on the rotation of the joints, but on the shape of what we were animating. Our animators work in all different ways. One person may pose it one way, and another might make the exact same looking pose but in a completely different way. So measuring the surface and determining the corrective shape based on that was the obvious solution. For the pain of those two months it took to fix Rhino, it was so worth it.”


Lasseter shared the story of Rhino’s conception. “We were at a story retreat when we were restarting the story. I brought everyone up to Sonoma where I live. My son has a chinchilla. I brought him over to the story thing and we put him in the ball. He was running around at the story meeting and it was hilarious, and the guys were laughing, and said, ‘we gotta do this’. They wanted to have this super fan notion, the ComicCon fan of Bolt. The combination of that ComicCon super fan rolling around in a ball is something so fun about that character.”

Rhino’s ball added yet another level of constraints. The software team wrote a program so the ball could transform around a surface and the ball would rotate correctly, and could be disabled if needed. By constraining the ball to Rhino, the animators could move Rhino to a new location and the ball would automatically roll to that location, perfect for simple forward running shots.

According to Kaytis, the collaboration proved extremely successful and well worth the effort. “When I animated my first shot, the one where he falls off the table and lands on the bench, that was the shot that had everything. He was on all fours, standing up, jumping in the ball, doing spirals in the ball, using all his corrective shapes. I was testing everything on this one shot and it all worked. If we hadn’t done all that stuff, The Cleanup Department would have been fixing inner penetrations. They would have had so much work.”


Once the Rhino rig was working properly, various details could be added such as animating the loose arm flesh, or ‘granny arms’. The granny arms were a normal deformer and worked with both IK and FK with the added ability to dial the corrective shapes in or out “so if one thing was conflicting with another you could tone it down. You would get the correction, but it was manageable by the animators, so you could animated in and out how much was being solved by the corrective PSD shapes.”

Pixar’s influence on the Disney pipeline meant the animation team could send Rhino back to modeling or rigging and they would send it back to Kaytis for testing, who would request changes and send the model back to them.

“For me,” said Kaytis, “that was the fun of the movie, solving these problems every day. It was so exciting. It is a model of how we make a rig now. You aren’t done until you are done. The modeler isn’t done until the animator is done, and before it wasn’t like that. Before it was very separate, and now it’s so successful to work tightly with that group, and everyone feels responsible for the characters. So now we define it that the character is done when we see a rendered shot and it’s approved. And until then, no one is off the hook.”




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