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MillimeterBreaking the Mold:Physics of Jell-O Inspires CGI Stars of Flubber
Feb 1, 1998 12:00 PM, Ellen Wolff
"Flubber is like a nice hood ornament made out of Jell-O" is ILM animation director Tom Bertino's description of the title character in the Walt Disney film. Bertino, whose team brought the CGI Flubber to life, also served as ILM's visual effects supervisor and helped director Les Mayfield come up with the character's jiggly green look. Bertino confesses to doing "a fair amount of R&D at the grocery store. I remember laying out jars of gelatinous, semi-transparent substances in the director's office and having very scholarly discussions about the transparency and viscosity factors that Flubber would have. Anyone from the outside would have thought we were crazy. There was one particular hair gel-I won't name it 'cause they haven't sent me my check yet-that we'd hold up to the light, shake it and say with a great deal of satisfaction, 'That's our hero.'"
Of course this "hero" had to interact with star Robin Williams, and in one scene Flubber behaves like a miniature "balloon animal" cradled in Williams' hands. Shooting the background plate of the actor relating only to his empty hands was actually fun, Bertino recalls. "Robin had to interact with blank air and convince you that there's a character there. It's a very tricky talent, but he has it in spades. I was working outside of camera range giving him visual and sound cues. Improvising schtick with Robin is a cartoonist's dream come true."
Also on set was ILM's Keith Johnson, head of the match move team that would later recreate the scene in the computer and provide Flubber's animators with an accurate virtual environment into which the CGI character would be inserted. To gather the necessary data, Bertino explains, "Keith took elaborate measurements of the distances from object-to-object and object-to-camera, as well as lens information." Armed with this data, Johnson's team would create an exact virtual representation of the room when the plate was shot. As Bertino notes, "It makes it quite easy to place your animated character in that environment when you have a bunch of CG models standing in for what was actually in the room, at proper distances from each other."
Once the background plate was scanned into ILM's Silicon Graphics computers, the match movers went to work. "We're able to bring up that clip in the computer in a Softimage 3-D environment," says Bertino. "The match movers then took what's seen on film and recreated it in primitive wire frame models." But he notes that "there's a little bit of animation involved in that-the dummy version of Robin in the 3-D environment had to be match-moved so that it was articulated and moving in the same way that the real Robin was. Even when a human is standing still, he's not absolutely motionless. You have to track every bit of that movement, otherwise there's going to be that fatal slip that's going to give you away, when Flubber turns out not to quite be sitting on Robin's hands. This match moving is very unforgiving-you either get it right or you don't-there's no gray area."
The match movers also provided the animation team with wire frame "eye cones" projected from Robin's eyes down to his empty hands. Using this information, the animators could make Flubber meet Robin's gaze in a convincing way. "Getting that eyeline working properly is an important part of the process," notes Bertino. The wire frame data is especially critical because it replaces the background plate during the animation process. "When the animator is actually doing his animation, he's really only looking at the match move object and environment," Bertino explains. "To load in the full picture every time would require the computer to crunch so many numbers that you'd never get done."
Animating Flubber "was a big challenge for the animators," says Bertino. "They had none of the usual crutches that you use for acting and emotion because the thing doesn't have a face-it definitely brings pantomime talent to the fore. To get that sort of elasticity we used a program that's part of the Softimage package that has actually never been used for character animation in a major feature film. It's called Metaclay, and it's sort of like modeling with clay in the computer. It's used more as a tool for liquid kinds of effects than for characters-I don't think anybody's ever had the nerve to try to make it act."
"It's a very different way from we're used to working in the computer, which tends to be in terms of absolutes and concretes, at least as far as the animators are concerned. Metaclay is a lot more of an intuitive animation tool, similar to hand-drawn animation where you redefine a character frame by frame. Flubber had to be continually molded and shaped to play his best angle to the camera."
Lighting Flubber was also difficult, Bertino recalls, "because it's a semi-transparent character. You see refracted backgrounds and light coming through it as well as bouncing off it-it definitely ups the ante. Transparency is definitely a processor killer, because you start getting up into very big numbers to get all that to play against itself properly."
"We basically used lights as they're attainable in Softimage and just set them up for the right angle and properties," explains Bertino. "However, the nice thing about computer graphics is that we could cheat the lighting where necessary to make Flubber look more appealing."
The final shot, which was rendered using RenderMan and some proprietary code, shows a Flubber that looks realistically solid even though you can see right through it. Bertino feels the key challenge of creating Flubber was to convey personality. "Audiences are so sophisticated and demanding now, there's really no trick to seeing unreal objects moving. The trick now is to get these characters to act."
Les Mayfield, director; Dean Cundey, director of photography; For Industrial Light + Magic: Tom Bertino, animation director/visual effects supervisor; Sandy Karpman, co-visual effects supervisor; Steve Bragg, computer graphics supervisor; Keith Johnson, lead match mover; Philip Alexy, lead technical animator
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