...computers are not making these films, people are

Pete Docter, Pixar

But Pete Docter, director of the animated movie Monsters, Inc., does not feel a warm glow of pride because of the money that his creation is generating. Even though the amounts involved are huge - Monsters, Inc. earned $63.5m in its opening weekend in the US.

Nor does he reserve his fondest regard for the story of the film, which concerns the lives of those monsters every child has seen lurking in their wardrobe shortly after the bedroom light is turned off.

Instead, Mr Docter is proudest of the fur adorning James P Sullivan - the shaggy two-metre tall monster who is the star of the movie - and the t-shirt of Boo, the child who causes havoc when she escapes into the monster's world. These items are a triumph for computer animation.

Good hair day

Every one of the 3.2 million hairs adorning Sullivan, or Sulley as he is known in the film, are individually animated. The cloth of Boo's t-shirt billows and folds just like real cloth. It is these that long-time animator Docter feels are the movie's real breakthroughs.

"Those are things that would not have been possible even three or four years ago," said Mr Docter.

Before now, Pixar's films featured characters with as little hair as possible, said Mr Docter. The toys in Toy Story and the insects from A Bug's Life all had hard bodies that are much more straight-forward to animate. The hair on any characters that had it was either very short, or tied back so it could be modelled as a single entity.

Pete Docter: Story and characters come first

But now as computer technology moves forward, more complex materials can be convincingly modelled.

This is not just a question of raw computer power. Animating those millions of hairs certainly soaks up huge numbers of computer cycles, but first Pixar had to find a way to realistically model the way that hair bends and flexes.

The animators modelled each hair as if it were made of a collection of springs and balls. Even then they could not animate each one individually. Sulley's shaggy coat has 500 or so "key" hairs that influence those around them and co-ordinate movements.

The result, said Mr Docter, was to make Sulley's fur a rich and complex material that moved as we would expect.

Computer artistry

But Mr Docter was keen to stress that Pixar is no slave to technology. Art comes first.

Toy Story was Pixar's first feature

"The story drives the technical," he said. "We think of a story and characters and then we say we need to have a main character who is blue, furry, with long hair, and then we come up with a way of solving it."

Solving these problems is no easy task. The software to animate the cloth took two years to write and fine-tune. The whole movie took five years to make.

The animators too were far more than just programmers, said Mr Docter. They are the ones that have to give life to the characters, endow them with personality, by working out how they will move and react to different situations.

"One important thing that people tend to forget is that computers are not making these films, people are," said Mr Docter. "The computer does not do anything - it just sits there if a human does not use it and it's really the people that are the creative elements."