Movie magic: go behind the scenes of Robots to discover the secrets to creating smash-hit animations

Science World, March 28, 2005 by Jeanna Bryner

Rodney Copperbottom isn't your typical kid. For one thing, he's made completely of metal. And if you were to look under his outer covering, you'd find a mesh of gears and springs. Rodney and his equally mechanical friends live in an all-robot world filled with flying machines and cool gadgets. This universe is the basis for Robots, an animated film created by Blue Sky Studios, the makers of Ice Age.

How does Blue Sky create such imaginative and visually stunning movies? To find out, Science World met Carl Ludwig, the studio's cofounder. Read on to learn how Ludwig and his team used junkyards, computers, and a unique lighting technology to bring Rodney's dreamlike world to the big screen.

How did Blue Sky dream up Rodney's world?

We visited places like junkyards to look for ideas for the characters and the movie's setting. Believe it or not, an aqua-blue boat motor was the inspiration for Rodney's appearance.

Even though the characters in the movie are robots, we wanted them to have humanlike qualities. Rodney, for example, is representative of most kids: He thinks everything is possible, and he tries to invent things that would make the world better.

Using the ideas we came up with, writers formed a script. With the story in mind, the art team drew sketches of the characters and their environments. Then, these drawings were modeled inside the computer using special software (see Nuts & Bolts, p. 10).

Do the characters move in a similar way as humans do?

Most of them do, except for Big Weld, Rodney's hero. He just rolls around like a bowling ball. To establish how a character moves each body part, we go through a computerized process called rigging. We use the computer to add little controls all over the characters' bodies. These controls are similar to the joints in your body, and they are attached to what look like puppet strings inside the computer. By manipulating these "strings" and controls, we make the characters move.

How do you combine each small movement to create an entire movie?

An animated film shows movement by flashing a series of still images, or frames, quickly onto the screen.

Say we want to show Big Weld placing his arm around Rodney. The animators, whose job it is to create these frames in the computer, design a set of images that show the movement in steps. For example: The first image in the series would show Big Weld with his arm at his side; the next would show his arm rising; and in the final image, his arm would be stretched around Rodney. And to ensure that each movement follows correctly from one frame to the next, the animators depend on the coordinate system (set of numbers that determines an object's position along the x- and y-axes).

One of the last steps in creating animated films is adding lighting. Why is lighting so important?

Lights really affect a movie's story line. If you use the same type of lighting for the whole movie, it would look boring. You wouldn't be able to tell the difference between a sunny day and a dreary one.

Since we don't have real lights in computer animation, we set up a lighting system inside the computer. One thing that makes Blue Sky unique is the lighting software program, or renderer, that we use. To design the program, we paid close attention to the physics of light in the real world.

This software program uses ray tracing. Can you explain this technique?

First, you need to understand that light travels in waves called rays. When light reflects, or bounces, off an object, some of the rays scatter back to your eyes. [That's how you see an image of the object.] But not all materials reflect light in the same manner. That's why some things look dull, and other things look shiny. Our software program understands these principles and uses them to treat light in Rodney's world.

A computer image is made up of tiny dots called pixels. The software fires a [virtual light] ray at a virtual geometric world, one pixel at a time. The ray tells the computer how light would bounce off each pixel if the spot were made of a real material. Then, the computer fills in the pixel and moves on to the next one, until the entire image is complete.

Can you give us an example from Robots?

Certain characters in the movie are sleeker looking than others--they resemble the latest gadget. One example is Ratchet, a slick businessman. We've designed him to look as if he's covered with brushed steel. His surface isn't completely smooth, so when light rays hit him, they get reflected at all different angles--a process called diffuse reflection. The scattered reflecting makes him look polished and satiny.

How does light affect Rodney, who isn't as sleek as Ratchet?

Rodney is also outfitted with metal, but it's covered with blue paint and rust. His material absorbs more light rays than a polished surface would. With less reflection, his covering appears duller.

For his eyes, we based the lighting on a transparent material like glass. Unlike metal, when a light ray hits glass, it travels through the glass before it bounces back. Also, the glass slows the rays, causing them to refract, or bend, when they enter and exit the glass. [The more the rays bend, the more they create a glistening effect.] So Rodney's eyes glisten.