DreamWorks Animation "Shrek the Third": Linux Feeds an Ogre

All the big film studios primarily use Linux for animation and visual effects. Perhaps no commercial Linux installation is larger than DreamWorks Animation, with more than 1,000 Linux desktops and more than 3,000 server CPUs.

“For Shrek 3, we will consume close to 20 million CPU render hours for the making of the film”, says DreamWorks Animation CTO Ed Leonard. “Each of our films continues to push the edge of what's possible, requiring more and more compute power.” Everyone knows Moore's Law predicts that compute power will double every one and a half years. A little known corollary is that feature cartoon animation CPU render hours will double every three years. In 2001, the original Shrek movie used about 5 million CPU render hours. In 2004, Shrek 2 used more than 10 million CPU render hours. And in 2007, Shrek 3 is using 20 million CPU render hours.

“At any given time, we are working on more than a dozen films”, says Leonard. “Each of those films has its own creative ambition to push the limits of CG filmmaking.” DreamWorks Animation employs about 1,200 people, with about two-thirds in their Glendale studio and the rest in their PDI studio in Redwood City linked by a 2Gb network. (Note that DreamWorks Animation, a publicly traded company led by Jeffrey Katzenberg, isn't Steven Spielberg's DreamWorks live-action that merged with Paramount recently.)

“There were many specific technical advancements on the movie, including advancements in hair, clothing, costuming and crowds as well as bringing the secondary character animation [crowds] to a whole new level of performance”, says Leonard. About 350 people are working on Shrek 3, with about 300 at PDI and 50 in Glendale.

In Shrek 3, Fiona transforms a bevy of classic “rescue me” fairy-tale princesses into action figures to defend the kingdom of Far Far Away from usurper Prince Charming. How to convert Sleeping Beauty's narcolepsy into a weapon or get neat-freak Snow White to dirty her nails fighting bad guys seem like minor challenges compared to the technical obstacles involved.

“DreamWorks Animation R&D provides the tools, libraries and software infrastructure for the creation of world-class CG films”, says Leonard. “We develop and support a suite of application tools for our films, including a proprietary animation system, lighting, rendering and compositing tools, and effects tools for things like fire, water, clothing and crowds, to name just a few.” Leonard estimates they have several millions lines of custom code, mostly written in C (legacy code) and C++ (newer code).

Andrew Pearce leads the DreamWorks Animation R&D group based at PDI. “Long hair may be the biggest technology advance in Shrek 3”, says Pearce. “In all of animation in the past you've seen long hair very little.” “It took months to do the hero-hair flick on Shrek 2”, notes Visual Effects Supervisor Philippe Gluckman. “Hair is everywhere in Shrek 3.” How hair glides across a shoulder looks easy but is very complicated to model. “The way the hair moves had to become much more automated”, says Gluckman. There isn't time for animators to position each hair by hand.

“With clothing we have more interactions, including ripping of the cloth”, says Pearce. “Fast motion is always difficult. In the real world, there's only so fast you can move, but nobody has told our animators that. If you went from 0 to 500 mph in one second, you'd probably leave some clothing behind in the real world.” Animation reality is as much art as physics.

Figure 1. Our print copy of this photo surely doesn't do justice to the astounding detail in the hair of the characters. (Photo credit: all Shrek photos in this article courtesy of DreamWorks Animation LLC.)

It isn't just the challenge of animating some clothing, it's how much clothing. “We have a lot more characters in the same shot”, notes Shrek 3 Co-Director Raman Hui. “Shrek 3 has a huge cast with 48 characters”, says Shrek 3 Director Chris Miller. “We have huge crowd scenes with 40 to 50 characters on a stage and 2,500 in the audience.” “The challenge in crowds is each character needs to look different”, says Pearce.

“If we had to do one setup for each character, that would take too long”, says Character TD Supervisor Lucia Modesto. “We take a generic character and warp that character. We have Man A, Man B and Woman. The big variation you get in a crowd scene is the silhouette of hair and hat. For characters in Shrek, we had one generic man with three variations, now that's 16. Women went from five to 25 variations and 13 hairstyles.” A lot of work is done to make known characters like Shrek look better, but without looking different.