<em>Alvin and the Chipmunks</em>: A Critter Christmas

Rhythm & Hues has become a digital Animal Farm with its animated virtual menageries. The studio created 500 CG shots for Alvin and the Chipmunks. All images ™& ©2007 Twentieth Century Fox and Regency Enterprises.

At the LA-based visual effects shop Rhythm & Hues, the "cute critter quotient" runs pretty high. Following R&H's Oscar-winning visual effects in Babe, the studio has animated virtual menageries for Mousehunt, Charlotte's Web [1], The Chronicles of Narnia: The Lion, the Witch and the Wardrobe [2] and The Golden Compass [3]. The veteran animation team also has created fanciful animal characters for Scooby-Doo and Garfield [4], so when Garfield director Tim Hill took on Alvin and the Chipmunks for 20th Century Fox Animation (opening Dec. 14), R&H was a natural choice to create 500 CG shots that the show required.

Todd Shifflett, who has worked on several of the shop's critter features, including Charlotte's Web and both of the Babe and Scooby-Doo movies, brought an experienced eye to the post of visual effects supervisor on Alvin and the Chipmunks. "This is the first time they've been animated in 3D," says Shifflett about the chipmunk trio of Alvin, Simon and Theodore that's famous for singing their perennially popular Christmas song. "The director wanted them to look like real creatures but not necessarily actual chipmunks. They're chipmunk-esque," he laughs.

The R&H team spent considerable time poring over the extensive archive of 2D material that's been amassed since Alvin and the Chipmunks debuted a half-century ago. Shifflett recalls, "There is a lot more than you might think. There was an episodic television show for children that ran for a long time, and they had versions in different countries. So it's been running pretty steadily for the last 50 years. The biggest usefulness of doing that research was to understand how each of the characters would react differently to different situations."

Translating well-known 2D cartoons into 3D required more than adding dimensionality and realistic fur. "These are quite a bit different than the 2D characters, which were the size of children," notes Shifflett. "It would have been a little too creepy to see giant furry things running around. Our chipmunks are probably three times actual size. There was certainly room to develop a different look.

"The most difficult part was establishing what they were actually going to look like. We went through a number of iterations -- beginning with something that looked like it came right out of the woods and had a much more realistic fur quality to it. But that was just a little too scruffy and not enough like a 'Hollywood movie star.' Yet if we pushed the look too far in the other direction, it started to seem just too cleaned up and too much like a stuffed animal. So trying to find a middle area that everyone was happy with was probably one of the biggest hurdles.

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R&H took months to shape the characters. They examined features like the size of the chipmunks' heads, the placement of the eye and the color of their fur. [5]

"The process of shaping the characters took months," Shifflett explains. "We went through everything from how big their heads were to where their eyes were placed. Then we had to establish how light or dark their fur would be. When you talk about an animal's fur color it's complicated, because there are deeper layers of fur -- there's an under pelt that contributes quite a bit to the fur's look, which you don't necessarily latch onto right away. If you make the under pelt dark and the outer pelt light, you get a totally different look than if you do it the other way around. There are lots of variations that have to be mulled over. Even when we look at an animal that we would consider being a solid color, there's actually quite a bit of variation. It's something that if you actually make it only color, you start to get a cartoony feel."

R&H used the same fur simulation tools that were employed to create the photorealistic lion in Narnia, and Shifflett explains that fur sims were run for Alvin and the Chipmunks. "Each character had to have a distinct hairdo built for it, and we were given some latitude in certain scenes when they get really excited. For example, if they're riding on the top of a remote-controlled car, we could blow the fur around."

Of course, real animals don't ride on toy cars, so R&H had to finesse variations on actual chipmunk behavior when creating the character animation. Shifflett recalls observing the behavior of real chipmunks as part of the research for the film. "Universal Studios has some chipmunks, and they were kind enough to allow us to come over and spend some time videotaping the animals. It was pretty fascinating to get up close and personal with real chipmunks. They're tiny and they move very quickly. We got them running to see how their muscles move and we could get a good sense of how their fur was combed and what their little mannerisms were like when they were standing and twitching."

While the behaviors of Alvin and the Chipmunks were stylized, Shifflett says that they were "dialed down a notch" from cartoon animation. "We did have the latitude to push the characters' expressions, but the director did want some naturalistic motion to make them feel like they were really in the environment." R&H used its proprietary software Voodoo to handle all the animation, which included animating the clothing that the chipmunks wear. "There were certainly some technical challenges, for example, in trying to make their sweaters look real. It's complicated when you stretch a sweater -- you don't want it to look like texture mapping. You want to make it feel like the actual cable knit is stretching."

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Although the behavior of the movie chipmunks is stylized, R&H dialed it down a notch from cartoon animation. [6]

Undoubtedly the most anticipated thing these chipmunks do is to perform their signature Christmas song, and Shifflett says, "They are quite adorable when they sing and dance. The production already had done choreography to the song using humans, and that was our reference for the type of dance that the chipmunks would do. Then we'd work it into their chipmunk bodies. If a particular movement didn't really work because of their body structure, we could figure out something else. But for the most part we were able to stay pretty true to the original choreography."

The film also called for Alvin to play a guitar, and Shifflett's team found a rich trove of reference videos on You Tube. "We'd get notes from the director about the kind of guitar playing that he wanted. Whether it was Chuck Berry or Jimi Hendrix or Pat Benatar, we were able to go to the Internet and pull up clips of these famous people and get some of their classic moves. The Internet has become a good resource for us. Finding reference footage is something that at one time would have been too costly. You'd be hard pressed to convince production that you needed to spend the time and money to do that!"

Since the CG chipmunks had to be rendered to match the lighting in the live- action background plates, Shifflett relied on High Dynamic Range Images captured on set for reference. "We have a cube with six cameras that gets 360-degree HDRIs. And that provides us with a lot of lighting information. It was a very big focus for us to make the characters look like they're part of a real environment." The CG was rendered using R&H's proprietary code.

Integrating the CG into the plates, especially in scenes where they interact with lead actor Jason Lee (as straight man Dave Seville), were among the most complex parts of the assignment. Lee, most recently known for his TV sitcom My Name Is Earl, did a great job of "reacting" to chipmunks that weren't really there, notes Shifflett. "We had little stuffed animals that were about the right size on set so Jason would get an idea of what their height was and where their eyelines should be. When it came time to shoot a take, we'd take the stuffed animals out. It's a pretty difficult task for an actor to be cognizant of that, all the while trying to remain in character.

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The most complex part of the job for R&H was integrating the CG chipmunks into the plates, especially in scenes where they interact with lead actor Jason Lee. This created challenges for R&H's matchmovers. [7]

"The chipmunks climb up on top of Jason while he's sleeping in bed and while he's in a car," Shifflett notes, which created challenges for R&H's matchmovers. "One of the unseen things that all visual effects rely on is tracking and matchmoving. It's something that when it's done well you never see it, but if it's done incorrectly it ruins the shot. The teams that do that don't get a lot of glamour, but they have a really difficult task and it's often pretty thankless. The animators get all the credit!" R&H's tracking tool is integrated into its Voodoo software.

The chipmunks also had to interact with human-sized props, and sometimes those props were real and other times they were CG, notes Shifflett. "We worked closely with the special effects unit, which did all kinds of wonderful rigging to help knock over props. But in a scene where Simon throws paper airplanes, I can't even explain how much time we spent on set trying to get a perfect throw of a paper airplane. Eventually we just built an airplane in CG."

The compositing of the CG elements with the live action was also done with Rhythm & Hue's proprietary tool Icy. Shifflett explains that the studio's multi-pass rendering approach permits a lot of flexibility during the compositing process. "We render the lighting -- which has several different layers including the key light, the fill light and the rim light -- broken out into separate passes. Then they are all recombined in the compositor. During the review process with the director, we'd often get a comment back that would say 'I'd like to bring them out more and have more kick to the rim light.' It's much easier now to accommodate those requests because we didn't have to go back and re-render. We can just go back to the composite. That certainly has become critical for us."

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The compositing of the CG elements with the live action was done with R&H's proprietary tool Icy. The studio's multi-pass rendering approach permits a lot of flexibility during the compositing process.  [8]

Shifflett credits the attention to detail that the compositors lavished on Alvin and the Chipmunks. "We had some compositors going off and shooting their own elements because they wanted to add something extra to a scene. It's great when people get that excited about the work."

"The biggest challenge on these projects is more the schedule than anything else," Shifflett admits. "Putting together a pipeline that runs smoothly without hiccups is an art form in itself."

One thing that didn't turn out to be problematic for Shifflett was having to listen to the chipmunks' high-pitched voices repeatedly singing their famous tune. "When we first got the assignment I thought, 'I don't think I can take listening to those voices as much as we're going to have to listen to them.' When I was little, I had the Chipmunks' punk album, though I didn't go and dig it out. But, oddly, it wasn't as bad as I thought it was going to be. They were very funny, appealing characters and I was amazed at how everybody responded when they watched these guys." But Shifflett does admit, "Those songs are still rattling around in my head. It will take a while to get them out of my system!"

Ellen Wolff is a southern California-based writer whose articles have appeared in other publications, including Daily Variety, Millimeter, Animation Magazine, Video Systems and the website CreativePlanet.com. Her areas of special interest are computer animation and digital visual effects.