Carolyn Soper Builds a Hamster Named Rhino
Carolyn Soper is a Vice President of Disney Animation Studios, and has been working on the upcoming Disney feature Bolt. She walked AnimfxNZ attendees through the process of building a hamster named Rhino.
Bolt is the story of a dog (played by John Travolta) who's the star of an action show. He believes anything he can do in the show, he can do in real life. He thinks he can knock down stuntmen and jump across 16 lanes of traffic. He thinks he's got laser vision. Unfortunately, he doesn't realize it's all fake. Bolt is owned by Penny (Miley Cyrus), whom he loves deeply and would do anything to protect.
The fun starts when Bolt gets shipped to New York, still believing he's got powers, and now believing Penny was kidnapped by the Man With Green Eye. So he does the only logical thing: he abducts a cat. Because all cats are evil and therefore agents of the Man With Green Eye, this one, Mittens (Susie Essman) will surely know where Penny is.
Partway along their quest, they find Rhino the hamster, Bolt's 'biggest fan.' So now there's this poor sane cat tied to a delusional dog and hounded by an equally delusional hamster.
Incidentally, Rhino's voice comes from an unlikely source: Mark Walton, who had done the scratch dialogue. Although normally that original scratch voice gets replaced by a big-name actor, Mark was so compelling as the hamster that the animators petitioned for him to stay on, and this counts as his big-screen debut.
They first started Bolt-a-palooza mid-December, and by the beginning of January they had a new Bolt rig. So it was natural for them to have confidence that they could do the same for Mittens, Penny and Rhino.
But when they were building Rhino's palooza poses, the commensurate rig had collapses and penetrations everywhere. So they were faced with a decision: keep adding transformers and corrections to the rig, or make a drastic change and completely overhaul it.
The radical change they went for required a complete change in workflow. Traditionally, animation involved a linear, three-step process: first the character would be modeled, then the approved model would go to rigging, and then the approved rig would go to animation. If it didn't work in animation, it would go back and forth with the rigging department until the problem was fixed.
So the linear walls were broken down, and instead a Character Team was created, where all three specialties could work together to create a character that worked.
When it came to creating the new rig, they had a few restrictions. They couldn't touch the existing quad rig, because it worked. They also couldn't build a totally separate rig (which would have required the director to send the hamster behind a bush every time it needed to go from four legs to two and vice versa).
The facial part of the rig was already built, and was working well. Fortunately, they had built it using a bolt-on facial system, which made it easy to rip off the body and put it on another skeleton.
So that's exactly what they ended up with: one skeleton, two skins, and one face, with a few blend shapes to transition from one to the other.
The next challenge was in the research and development of a new system for corrective shapes. If you bend your arm in real life, the flesh bends and squishes in certain ways. When you create an arm on a computer, though, and then instruct it to bend, it doesn't know how to fill in that flesh.
The solution to this problem is in something called a Post Space Deformer, or PSD. What it does is take the desired, properly squished end shape, and then reverse calculate what the original shape would have to look like to get there. This new shape – called a 'delta shape' – gets blended in as the original shape is transitioning.
The issue with PSDs is that every time you have a new end position, you have to build a new delta shape. And when it came to Rhino, every movement created a shape that needed correcting. He was fat and fluffy. He was potato-shaped. He had short arms and legs. All these problem areas overlapped, so if you solved one problem, like the neck, you might create more problems with another area.
As if things weren't complicated enough, some Disney animators use a broken rig, which means they can position each piece of the body independently.
So the folks at Disney created a totally new solution: instead of creating the PSDs by joint rotation and final position, they created them based on the relationships between the body parts. So the PSD created by dropping Rhino's right ear towards his shoulder was the same as the one created by him lifting his arm.
Using Lorez mesh-based distance locators, they created distance values for the PSD drivers that would work regardless of whether the animator had rotated, translated or scaled the character. Clay Kaytis, the Supervising Animator of Rhino, was also given control over how much he wanted to use the PSDs.
As an added bonus from all this development, poor Rhino was given something most of us would rather avoid: granny arms. Based on the trailer we saw, though, you won't be focused on the PSDs or the cutely swinging granny arms. You'll just be enjoying a great story.
Kaila Colbin, the founder of Missing Link, is a frequent contributor to a variety of magazines.