Animation explained as Pixar expert counts us in on software's key sums

Published on Friday 3 April 2009 19:56

David Baraff, one of Disney's research and development team, tells Peter Ranscombe how cartoon equations work

WHETHER it's through cute and cuddly monsters helping a lost wee girl, or a talking rat helping a hapless chef to cook, Disney's Pixar Studios has redefined how we look at animation, enthralling a generation of children – and their parents too.

From Toy Story and Finding Nemo through to Wall-E and the forthcoming Up, the studio has mesmerised with compelling stories and smooth graphics. And the secret to the animators' success? Mathematics.

When Nemo wiggles his good flipper or Woody shouts "Yee-ha cowboy", their actions are guided by a string of numbers and equations that have been fed into specially written software.

David Baraff, a member of Pixar's research and development team, will be at the Edinburgh International Science Festival on 14 April to give a Filmhouse audience an insight into the maths used to create Ratatouille, his studio's 2007 offering.

His talk – organised by the International Centre for Mathematical Sciences, run jointly by Edinburgh and Heriot-Watt universities – won't delve too deeply into the complex equations used to bring animated characters to life, but it will give children and adults alike a flavour of what goes on behind the scenes in a Pixar film.

"I wouldn't call myself a 'real' mathematician," explains Mr Baraff. "I tend to skim the surface but over a fairly broad range of subjects – so I'm not an expert in any one thing but I know a lot about a lot of different subjects, which is what I need for my work."

His work stretches from 2001's Monsters Inc through to his current project, Toy Story 3, which is due to hit cinemas next summer. Mr Baraff and his colleagues write "dynamic software" that complements the work carried out by the studio's artists.

"We have these wonderful animators who pose and animate the characters over time – they figure out where all their hands and legs are, and their facial expressions," he says.

"They can't be concerned with doing things like posing their clothes and dictating how their clothes should wrinkle and move around – so we need to create software that automatically takes care of these kinds of things and figures out what it's supposed to do. (It] basically acts as a behind-the-scenes brain to figure out what these things should be doing on their own."

He continues: "The first film in which you would have seen the fruits of my labours was Monsters Inc. The standout thing there was the big monster – Sullivan – with his fur, which moves around quite a bit. That's our software. In Monsters Inc, the little girl is also wearing clothes and those are simulated. After that, you will also have seen some of my work in Finding Nemo. There's not a lot of clothing in that, but one of the things we did there was some water simulation in various parts of the movie.

"Following that, the really two big ones for me are The Incredibles, which has clothing and hair all over the place and then after that Ratatouille."

Although Mr Baraff's background is in computer science – with a healthy dose of maths thrown in – his day-to-day work involves a lot of physics. He says: "My father is a physicist and I tried physics in college but I really didn't like it and wasn't particularly good at it. So I find it ironic that, years later, I find myself doing something that physics is one of the keys to getting it right."

Pixar certainly has been getting things right: the studio's Renderman software won an Academy Award in 2001 and the programme has been used in 47 of the past 50 films nominated for the Best Visual Effects Oscar. Renderman has been used in movies as diverse as Indiana Jones And The Kingdom Of The Crystal Skull and Forrest Gump.

So which mathematical techniques are used to make the clothing and hair flow with the characters we see on screen?

"A lot of different things come into play – it's pretty broad," Mr Baraff says. "There's a lot of maths for computer science where we're concerned with how fast computer programmes will run – I would call those computational algorithms. There's a lot of maths in studying the properties of surfaces and shapes, which comes into play when you're doing the clothing – I would call that differential geometry. We also use a lot of linear algebra."

Each film brings new challenges for Mr Baraff and his fellow software developers – Toy Story 3 has brought about a further fundamental shift in the way that Pixar models clothing. After Wall-E – which Mr Baraff describes as his "off movie" because he wasn't required to render clothes or hair – he is right back into the thick of the action.

But does he have a favourite from the movies he has helped to create? "If I looked at it visually, then without a doubt the clothing that came out of Ratatouille is my favourite. I feel it is just so beautiful and we really loved how it looked in its artistry," he admits.

"In terms of watching it – that's a very interesting experience. If you've worked on a movie hard enough then for any two or three seconds of the film that you're watching you'll tend to flash back to when you were working on that particular section. It can take a few years until you can sit down and really enjoy it. But story-wise, I would say my favourites have been Ratatouille, The Incredibles and Wall-E. I really like Wall-E because it's a love story and I really like love stories."