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Breaking the Mold:Physics of Jell-O Inspires CGI Stars of Flubber

“Flubber is like a nice hood ornament made out of Jell-O” is ILM animationdirector Tom Bertino’s description of the title character in the WaltDisney film. Bertino, whose team brought the CGI Flubber to life, alsoserved as ILM’s visual effects supervisor and helped director Les Mayfieldcome 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 ofgelatinous, semi-transparent substances in the director’s office and havingvery scholarly discussions about the transparency and viscosity factorsthat Flubber would have. Anyone from the outside would have thought we werecrazy. There was one particular hair gel-I won’t name it ’cause theyhaven’t sent me my check yet-that we’d hold up to the light, shake it andsay with a great deal of satisfaction, ‘That’s our hero.'”

Of course this “hero” had to interact with star Robin Williams, and in onescene Flubber behaves like a miniature “balloon animal” cradled inWilliams’ hands. Shooting the background plate of the actor relating onlyto his empty hands was actually fun, Bertino recalls. “Robin had tointeract 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 outsideof camera range giving him visual and sound cues. Improvising schtick withRobin is a cartoonist’s dream come true.”

Also on set was ILM’s Keith Johnson, head of the match move team that wouldlater recreate the scene in the computer and provide Flubber’s animatorswith an accurate virtual environment into which the CGI character would beinserted. To gather the necessary data, Bertino explains, “Keith tookelaborate measurements of the distances from object-to-object andobject-to-camera, as well as lens information.” Armed with this data,Johnson’s team would create an exact virtual representation of the roomwhen the plate was shot. As Bertino notes, “It makes it quite easy to placeyour animated character in that environment when you have a bunch of CGmodels standing in for what was actually in the room, at proper distancesfrom each other.”

Once the background plate was scanned into ILM’s Silicon Graphicscomputers, the match movers went to work. “We’re able to bring up that clipin the computer in a Softimage 3-D environment,” says Bertino. “The matchmovers then took what’s seen on film and recreated it in primitive wireframe models.” But he notes that “there’s a little bit of animationinvolved in that-the dummy version of Robin in the 3-D environment had tobe match-moved so that it was articulated and moving in the same way thatthe real Robin was. Even when a human is standing still, he’s notabsolutely motionless. You have to track every bit of that movement,otherwise there’s going to be that fatal slip that’s going to give youaway, when Flubber turns out not to quite be sitting on Robin’s hands. Thismatch moving is very unforgiving-you either get it right or youdon’t-there’s no grayarea.”

The match movers also provided the animation team with wire frame “eyecones” projected from Robin’s eyes down to his empty hands. Using thisinformation, the animators could make Flubber meet Robin’s gaze in aconvincing way. “Getting that eyeline working properly is an important partof the process,” notes Bertino. The wire frame data is especially criticalbecause it replaces the background plate during the animation process.”When the animator is actually doing his animation, he’s really onlylooking at the match move object and environment,” Bertino explains. “Toload in the full picture every time would require the computer to crunch somany 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 emotionbecause the thing doesn’t have a face-it definitely brings pantomime talentto the fore. To get that sort of elasticity we used a program that’s partof the Softimage package that has actually never been used for characteranimation in a major feature film. It’s called Metaclay, and it’s sort oflike modeling with clay in the computer. It’s used more as a tool forliquid kinds of effects than for characters-I don’t think anybody’s everhad 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 asthe animators are concerned. Metaclay is a lot more of an intuitiveanimation tool, similar to hand-drawn animation where you redefine acharacter frame by frame. Flubber had to be continually molded and shapedto play his best angle to the camera.”

Lighting Flubber was also difficult, Bertino recalls, “because it’s asemi-transparent character. You see refracted backgrounds and light comingthrough it as well as bouncing off it-it definitely ups the ante.Transparency is definitely a processor killer, because you start getting upinto very big numbers to get all that to play against itself properly.”

“We basically used lights as they’re attainable in Softimage and just setthem up for the right angle and properties,” explains Bertino. “However,the nice thing about computer graphics is that we could cheat the lightingwhere necessary to make Flubber look more appealing.”

The final shot, which was rendered using RenderMan and some proprietarycode, shows a Flubber that looks realistically solid even though you cansee right through it. Bertino feels the key challenge of creating Flubberwas to convey personality. “Audiences are so sophisticated and demandingnow, there’s really no trick to seeing unreal objects moving. The trick nowis to get these characters toact.”

Les Mayfield, director; Dean Cundey, director of photography; ForIndustrial Light + Magic: Tom Bertino, animation director/visual effectssupervisor; Sandy Karpman, co-visual effects supervisor; Steve Bragg,computer graphics supervisor; Keith Johnson, lead match mover; PhilipAlexy, lead technicalanimator

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