The G-Force guinea pigs needed to hold their tools, so Imageworks made a toe look more like a thumb All images © Disney Enterprises Inc..

Hoyt Yeatman, the VFX vet, has been nurturing G-Force for six years, ever since his then pre-school son first hatched the notion of guinea pig superspys. The concept took hold immediately when Yeatman did some research and discovered that there was more scientific validity to the concept than one would imagine. But realizing this rather unique hybrid took a lot longer than expected for Yeatman, who chose to direct as well. He even pitched to Michael Bay early on before enticing veteran producer Jerry Bruckheimer (Pirates of the Caribbean).

As if animating a guinea pig geek squad to combat a giant robot and matching the CG to the live-action plates wasn't challenging enough, Yeatman also decided to add stereoscopic 3-D to the mix as a post conversion. Thankfully, he was in great hands with Sony Pictures Imageworks, which not only excels at hybrid films with CG characters but also at 3-D. Scott Stokdyk (Spider-Man) handled vfx supervision, Troy Saliba (Monster House) served as animation director and Rob Engle (Beowulf) led the stereoscopic team. In fact, G-Force turned out to exceed even Spider-Man 3 in both shot count (1,287) and complexity (480 CG shots, 61 minutes of vfx screentime, 128 character rigs, including 15 robot rigs, and 1,861 total 3-D shots). (Engle serves on a G-Force 3-D panel next Thursday at SIGGRAPH 2009 in New Orleans, Room 260-262.)

"Because of the way we were shooting it, we pushed all the 3-D decision making into post, so it was like a DI suite," Yeatman says. "We called it the "depth grade suite," where we went in and customized how the depth was going to work from cut to cut."

Making this hybrid work smoothly offered its own set of challenges: "We developed sequences that were heavily animated, and trying to build background plates out of live action can be a real pain, because suddenly you're locked into something that needs to evolve," Yeatman adds.

"I'm very proud of the lighting and what I've found over the years is that when you have to put photoreal characters or environments in CG one of the problems is matching all the specular highlights and to make it look like it fits. The DP, Bojan Bozelli, overexposed and over-processed the negative and what that would do is increase the dynamic range of the Kodak Vision 3 to almost 11 stops."

According to Stokdyk, G-Force provided a great opportunity to showcase Imageworks' character animation and the whole film was built around letting the performance come out and letting the animators have some fun to tell the story. "We shot it in a way to facilitate that: we tried to get plates for everything we could. And we worked really hard to get close to the ground and work with depth of fields to have sweet spots for characters to live in. We tried to capture all of the areas and environments on film so we could track the characters in. And then we'd do the standard surveying and photography of a lot of the backgrounds.

"I think what gave Hoyt a real advantage being a first-time director was it was his idea and his baby. If there were any questions story or character related, it was all in his head. That is what I hope for out of any filmmaker, which is a clear direction of what the story is and who the characters are. In terms of doing the visual effects, of course, he's been where I was on a movie so many times, so in many ways he just let me do my job and trusted me and we had a great shared language. It was actually very easy for me to get into his head what he wanted look wise. We had a shared language of how to balance light and key and fill and specular highlights and subsurface. We just used our short-hand and went where we needed to go.