Toy Story was produced for Disney by the computer animation company Pixar and is essentially a comedy-adventure buddy picture. "The whole notion of a buddy picture is that you create two characters who are polar opposites and you put them in a situation where they have to work together and grow. You can see the whole arc of the character's development and that allows for some really great acting," says the director, John Lasseter. And despite the actors just being lines of computer instructions, the acting in Toy Story is very good.
As in almost all films, the plot was mapped out on story-boards. Sets were then created, but inside the computer. These were three-dimensional places in which the "actors" could move and live out the story. They were designed and then set-dressed to look more realistic. Virtual painters were even assigned to make them look more lived in.
Once the actors were in place, "cameras" could be positioned. Of course these were not real cameras, but perspectives adopted in a mathematical world by the computer.
Close-ups, medium shots, wide shots, tracking shots using dollies and cranes were all used, although there was no crane, of course. With no restrictions, the temptation to go for the clever super fly-by or the endless tunnel shot was hard to resist, but the crew did not succumb to temptation.
"We're trying to do something different and better than the work traditionally produced in computer graphics," says the supervising layout artist, Craig Good. "The problem is, until a few years ago, only people with PhDs could operate the software. It was like having paintings done by the chemists who mix the paint."
Toy Story deliberately borrows shots from live-action directors, and the crew even named their camera actions accordingly. "Branagh-cam", based on a shot in Frankenstein where the camera circles around the action, is used in the film when the other toys think that Woody has deliberately pushed Buzz out of the window and they all attack him. "Michael Mann-cam", based on some of the shots that director perfected in Miami Vice, where he would lock a camera on the spinning wheels of a Corvette, is used in a menacing scene in a petrol station.
Computers can store information precisely and share it, so shots can be worked on by several different teams at the same time, building up the final image layer by layer. This meant that basic camera angles, set- layout and actors' movements within sets were established before the individual departments began work on Toy Story.
The animation of the characters within the set is a hugely complex and labour-intensive task. Animators receive a shot with most of the shapes (including the characters) represented by rough blocks called polygons or by wire-frame figures. Most of the characters are represented by their skeletons with fully articulated joints and limbs that accurately reflect how the character can move. In many ways, this basic animation is much like the work of Ray Harryhausen in Jason and the Argonauts, made in 1963.
These simplified characters allow the computer to work faster and the animator to focus solely on the acting. "All you're left with to get across your meaning is movement and timing, which is fine, because that's the essence of animation," says the directing animator, Rich Quade.
Once the basic animation is complete, the detailed movement and expression of the character is worked on. The tools for this task are the animation controls, or "avars", which are built into the models like the strings on a marionette. Woody has more than 700 avars, and 212 controls in his face alone. But they are essential. Woody has to be able to show real emotion with real facial expressions, says the supervising technical director, Bill Reeves. "It isn't enough just to give the character anatomy. You've got to give it acting power."
When the animators have finished with a shot it is then put through other processes - shading, lighting and, finally, full-colour rendering. "Shaders" are computer programs that create the "real" surface appearance: the colour, the texture, the reflectivity, the irregularities and bumpiness. Technically, the various shaders (1,300 shaders were written for different surfaces) tell the renderer (the person in charge of the final touches) how various surfaces reflect light. The shaders take a basic mathematical model that represents a real surface and breathe life on to it.
The most dramatic transformation of a shot occurs in final lighting. The lighting crew can use every imaginable light source - including the sun and the moon. But the Toy Story lighting team never had to wait for the sun to come out from behind a cloud. There are virtual key-lights, back-lights and rim-lights. In one shot 32 lights were used, and in another there are five lights shining just on Mr Potato Head's ear.
One of the greatest joys for the lighting team was the easy control of shadows. The difficult trick for traditional cinematographers is to hide shadows or to keep them out of shot. In Toy Story, if the lighting team didn't want a particular shadow, they simply told the computer to make whatever was casting the awkward shadow transparent.
The process of creating the final detail and colour of an image is called rendering. This involves collecting and combining data for each image. This is built up from the shape of the objects in the scene and their pose and the lighting. The computer then has to work out how light would reflect around the scene and the colour and brightness of each of the 1,416,192 picture elements in every frame. It took over 800,000 machine hours to "render" the final footage using 117 powerful Sun computers running 24 hours a day.
When all these hi-tech procedures are completed, their remains one last, rather archaic, process. The computers display the image on a screen and, frame by frame, the movie is recorded on film.
Toy Story will neither transform the animation world in cost terms nor speed up the production of animated films. At least not yet. In its best production week, Pixar managed to produce three and a half minutes of completed animation. But Toy Story does break new ground in two different ways. Firstly, it opens up a whole new world of animation. While Disney has used computer-controlled processes in several movies, the films themselves remain essentially two dimensional. In conventional cel animation, the camera can normally only move sideways, pull up or zoom in. In this 3D world any camera angle is possible, and Pixar says a third of all the shots in the film involve a moving camera.
Secondly, and perhaps more fundamentally, Toy Story may end up challenging parts of mainstream movie-making practice. Some of the exteriors are so lifelike, that perhaps future car chases can be "shot" inside a computer. Already Hollywood producers are using digital stand-ins for actors in difficult shots, and the increasing use of unobtrusive computer-generated imagery in major pictures like True Lies and Apollo 13 can only mean that more and more digital production is likely.
Toy Story was a huge success in the US. But John Lasseter's greatest achievement is not that he has produced a movie that is very clever, but that, using such cumbersome technology, he has produced a movie that is very enjoyable.
"We're storytellers who happen to use computers," explains Lasseter. "You can dazzle an audience with new technology but in the end people walk away from a movie remembering the characters."
n `Toy Story' is on general release from tomorrow