Guinea Pigs to the Rescue

VFX guru and helmer Hoyt Yeatman discusses the gee-whiz 3-D effects of G-Force.

It all started in a five-year-old boy’s imagination. Several years ago, the son of Oscar-winning effects artist Hoyt Yeatman brought a guinea pig home from school, and then started imagining the animal as a commando. ‘He was very into G.I. Joe at the time,’ Yeatman laughs. But the seed of the idea took root, and six years later, Yeatman is making his directorial debut with G-Force, a G-rated adventure that can be easily pitched as Mission: Impossible with guinea pigs.

Released by Disney and produced by action-film impresario Jerry Bruckheimer, G-Force has animation and visual effects by Sony Imageworks. This hybrid of CG and live-action features photoreal CG critters voiced by Sam Rockwell, Tracy Morgan, Penelope Cruz, Nicholas Cage, Steve Buscemi and Jon Favreau. Upping the ante, Disney is releasing G-Force in 3-D stereo as well as in 2D

Yeatman has worked on 3-D special venue films, so at first he tested the idea of shooting the live-action portions stereoscopically. ‘But the console you drag around is the size of a sofa,’ he says. ‘And you’re forced to make three-dimensional decisions in the field, so you can paint yourself into a corner editorially. This is a Bruckheimer film, with fast cutting. There are around 2,000 shots in 85 minutes, and it’s probably 80 percent animation. A Pixar movie has about 1,100 shots. Our challenge was to make an animated feature within the walls of a visual effects production.’

Working with Imageworks’ Oscar-winning vfx supervisor Scott Stokdyk, (Spider-Man 2) Yeatman opted to capture the G-Force live action on film. ‘The ARRI 235s are the size of a loaf of bread,’ Yeatman enthuses. Then, as a post process, Rob Engle’s Imageworks team would create the 3-D stereo version with CG characters and vfx comped in. Yeatman believes that ‘dimensionalizing’ live-action footage in post is more straightforward than having left- and right-eye views of a scene shot in 3-D and trying to calculate three-space and add CG characters. ‘It’s a huge problem,’ he asserts. ‘If you can delay your 3-D decisions until after your film is cut, you can do interesting lensing and camerawork that you’d never be able to do otherwise.’

Yeatman used every visual effects trick to film G-Force‘including capturing footage from the guinea pigs’ POV. ‘We used a ‘Fisher-Price’ rig’a little pushcart that the camera sat on,’ he explains. ‘Our DP, Bojan Bazelli, created interesting camera moves in a nine-inch-tall world. And each time we shot, we used an HDR-Cam system that I built about two years ago, which is like a light probe that documents the set lighting. Our job was to document the DP’s lighting so that Sony could use the data directly in lighting the CG characters. It’s difficult to light characters and make them match the color and intensity of plate photography. Post-production artists usually have little data about that lighting, and they’re evaluating images based on a monitor that doesn’t show the entire dynamic range that’s available within the film negative. We did about 1,600 scenes with the HDR-Cam, and then Sony wrote a very elaborate lighting pipeline based on that.’

Animation supervisor Troy Saliba’who was ready for guinea pigs after working on Stuart Little 2‘led the Sony animators who brought the G-Force creatures to life. ‘Everything is keyframe Maya animation. There was no mocap,’ Saliba explains. ‘These guinea pigs have some stylized qualities’their eyes face a bit more to the front’but they had to move like photoreal guinea pigs. We had a bit of latitude because guinea pigs don’t stand on two legs and talk, but they had to move in a way that feels like if a guinea pig could stand up and talk, that’s what it would look like.’

‘We shot a lot of video reference, and Hoyt had a cage full of guinea pigs that we studied,’ Saliba recalls. The Sony crew also saw a Maya-animated demo that Yeatman had produced to pitch the original idea to Bruckheimer. ‘These guinea pigs are stylized so that they can physically do what they needed to do, and it was tempting to make their arms longer to look more heroic. But Hoyt was dead set against that and I was glad. It’s funny to see tiny little arms doing athletic secret agent moves.’

‘The hardest part was keeping the characters in frame with human actors,’ notes Saliba. ‘There’s a huge discrepancy in size.’ Yeatman had his actors handle hairless guinea pigs’later rotoscoped out’which provided Sony with good muscle references. Saliba explains, ‘We kept our geometry close to real guinea pig shapes. The cute fuzziness comes from the hair. There were much more realistic interactions when they touched each other, or when something brushed up against them.’ This wasn’t a trivial concern, since these critters wear parachutes and high-tech gizmos.

The composites of characters with live action’including chases through real streets and against pan-and-tile backgrounds’were painstaking. Saliba notes that some scenes were better achieved in all-CG, including those with an 80-foot-tall robot. ‘We have epic long shots and we go inside him with the guinea pigs, so he’s both a character and an environment.’

Yeatman concludes, ‘This is one of the most complex films I’ve ever worked on, let alone directed.’ And it turned out that his son’s idea of ‘commando’ guinea pigs wasn’t so far-fetched. ‘If you Google ‘Squirrels in Iran’ you’ll find that 12 squirrels wearing A/V equipment were captured in the Iranian Embassy!’

Disney’s G-Force is currently playing in theaters across the U.S.