Issue: Volume: 22 Issue: 11 (November1999)


Sometimes everything about a movie can be right--story, direction, acting, and art--yet the movie becomes a box-office disappointment. It happened this summer to The Iron Giant, an animated feature from Warner Bros., based loosely on the 1968 story Iron Man by British poet laureate Ted Hughes and directed by Brad Bird, who has also directed the animated TV show, The Simpsons. The movie received glowing reviews on the Internet from moviegoers and in the press from movie critics. Harry Knowles, influential host of the Ain`t It Cool News movie Web site, raves, ". . . purely and surely, one of the greatest films, animated or live-action, I have taken into my heart." This month, Warner Bros. plans to release video and DVD versions, and reportedly will launch them with a new marketing campaign.

The Iron Giant takes place in the small town of Rockwell, Maine. It`s 1958. Russia has launched Sputnik and plunged the US deep into Cold War paranoia. The story centers on Hogarth Hughes, a headstrong nine-year-old voiced by Eli Marienthal; his single mom Annie Hughes (Jennifer Aniston), a waitress in a diner; the Iron Giant (Vin Diesel), a 50-foot robot who drops from the sky; Dean McCoppin (Harry Connick, Jr.), a beatnik junk dealer and sculptor; and Kent Mansley (Christopher McDonald) an over-zealous government agent. One night when Hogarth is home alone watching TV, the transmission suddenly stops. He quickly sees why: The antenna is missing. Determined to find it, he follows a clear path through the woods that leads to the power station. There he spots a 50-foot-tall "metal man" munching the antenna, power towers, and other metal parts. When Hogarth switches the power off to save the robot from electrocution, he earns the Iron Giant`s loyalty. Meanwhile, Mansley, who has heard rumors of this alien monster, becomes determined to find and destroy it.

Made with 7000 parts, the Iron Giant is a 3D model created in Maya, rendered as a cartoon in Renderman, then imported into Cambridge Animation Systems` Animo.

All the characters in the film are 2D animations created in Cambridge Anima-tion Systems` (Cambridge, UK) Animo, with the notable exception of the Iron Giant himself, the first title character in a 2D animated film to be created with 3D computer graphics. The Giant was modeled with Alias|Wavefront`s (Toronto) Maya, rendered with Pixar`s (Pt. Richmond, CA) Renderman, and imported into Animo. "We chose to do the Giant in 3D because he did not belong in the Rockwell, Maine, cartoon world," explains Tad Gielow, CGI department head at Warner Bros. "By using CGI [3D computer graphics imagery], we could give him a different feel and a more mechanical look than the 2D characters."

To build and animate the Giant and create software that would render him as a cartoon in Animo-friendly formats, Gielow organized a team of 34 technical developers and directors. The team was so successful they found themselves creating 3D props--51 in all, according to Gielow. "The pipeline was very efficient," he says. "We did over 1000 feet of prop work that was not in the original plan." Among the props were machines such as jeeps, cars, trucks, tanks, bicycles, motorcycles, and jets, as well as things the Giant interacted with, such as junk in the junkyard, parts from the power station, train tracks and railroad ties, and a rock. Most difficult, though, was the Giant himself.

The Giant required more than one model: In addition to creating a "normal" Giant, digital sculptor Hiroki Itokazu used Maya to create a broken Giant, a battle Giant, and the Giant as a sculpture. The normal Giant has 7000 parts; the Battle Giant has 10,000 parts.

In order to place the Giant into the animation, every visible surface of those parts had to be rendered as a "toon," that is, inked, painted, and converted into Animo files. To do that, they needed to convert Maya files into Renderman RIB files and the 2D rendered output into Animo format. With no commercial software available in 1997 to do this, they began "rolling their own." Andy King worked on the Maya conversion; Brian Gardner created an entire image-processing pipeline, now named "Gartoons," to render the models and create Animo Layer Files.
In this scene, Hogarth is a hand-drawn element. The Iron Giant and the railroad rails and tracks are 3D models.

"Brad Bird was keen to have the CG look like hand-drawn animations from the `40s," says Gardner, "but it struck me that although CG [3D computer graphics] has worked for backgrounds in film, it has not worked very well for characters," he says. Thus, when Gardner received the mandate to create a system for The Iron Giant, he began interviewing people in the color-modeling and mark-up departments to learn what they needed to make a CG character fit into hand-drawn animation. He discovered that they wanted to receive Animo Level Files that were inked and painted but not irreversibly; that is, they wanted the option to change the colors of the rendered images.

The first problem to solve was producing inked lines that correctly defined the Giant`s parts and looked hand-drawn. Using Renderman, Gardner created a Gartoons shader that drew textured lines of varying thickness, a technique he named "line glomping." In addition, he added line wobble to Gartoons to create temporal antialiasing from frame to frame. This allows rendering on "twos" (every other frame) so that the CG animation will match similarly drawn 2D animations without strobing. And, as requested, Gartoons produces several ink, paint, and matte layers as Animo Level Files, each controlling such things as line color and matting for tone, highlights, and effects.

To avoid rendering separate passes for each layer, Gardner created plug-ins for Renderman`s device drivers as well as for the shaders. Device drivers care about entire images in 2D space, he explains, while shaders care about single pixels in 3D space. By encoding 17 channels of color and surface attributes into three color channels that are fed to a device driver and later expanded, Gartoons can render everything in one pass. The result can be a particular Animo layer needed by a department or a preview of a composite image. Gartoons can put each layer into a separate buffer, then display a composite image, which allows a kind of interactive rendering as colors are changed. "Once the buffer data is recalculated, the screen is repainted," Gardner says.

To animate the Iron Giant, Warner Bros. used Maya. To render him as a `toon, the studio created custom plug-ins for Renderman.

In addition to Gartoons, another innovative tool used for the film was a 3D/2D camera integrator that Gielow created as a plug-in for Maya. "This allows animators to match the Giant to the layout," he says. The blend seems to have worked well enough to draw people into the story and capture the hearts of children and adults alike. Adults like the witty satire and the message that we can choose not to be weapons. And one six-year-old posted this review on the Internet Movie Database site ( "I liked the Iron Giant. They tried to hurt him because they didn`t understand him. That`s not nice. You have to try to get to know someone . . .This was a good story without so many songs, and it made me interested for a long time."

Barbara Robertson is Senior Editor, West Coast, for Computer Graphics World.