Here’s how Pixar animated Monsters University (behind-the-scenes)

Pixar’s animated films feature magical characters like Sully, the furry 1,000-pound beast from Monsters University. Building those computer-animated characters takes years of work, but studio engineers showed how they streamlined that process with the latest high-end graphics computers at Nvidia’s GPU Technology conference in San Jose, Calif.

Above: Pixar’s Dirk Van Gelder on storyboarding animation

Image Credit: Dean Takahashi

In a keynote talk on Wednesday, Pixar engineer lead Dirk Van Gelder and technical director Danny Nahmias showed some of the most complex scenes from the film Monsters University and how much more difficult they were to create than the scenes from Monsters, Inc. a dozen years earlier. The talk showed how animation is pushing the high-end of the computing business in order to produce the entertainment that is enjoyed by hundreds of millions of fans. It highlighted more technical, super-geek details than we covered in our series on the making of Monsters University last year.

“This is the very leading edge of complexity in computing,” said Greg Estes, vice president of marketing at graphics chip maker Nvidia and a longtime follower of technology and entertainment, in an interview. “The GPUs can to the lighting and rendering in real-time in ways that were never before possible. They can play around with it more, do more iterations, and get it just right before they render it.”

With Monsters University, which debuted last year and generated worldwide revenues of $743 million, Pixar doubled its computing power and brought in a lot of graphics processing unit (GPU) servers to handle the workload of making and rendering the film. It had 270 people working for as much as four years on the movie, which was the first time Disney’s Pixar division ever did a sequel.

Pixar created its Renderman animation system in the 1980s and even made its own Pixar Image Computer hardware in 1987. It made four films, including its debut film Toy Story, with Silicon Graphics computers. But since 2001, its last 10 films have been made with armies of Nvidia graphics chips, said Van Gelder.

I took a tour of Pixar’s headquarters last June. Inside the building is a data center full of humming servers — double the size that the company used in the past — that would be considered one of the top 25 supercomputers in the world. The 2,000 computers had more than 24,000 cores. The data center was like the beating heart behind the movie’s technology.

Even with all of that computing might, it still takes 29 hours to render a single frame of Monsters University, supervising technical director Sanjay Bakshi, told me last year.

Rendering means that the computers build the 3D world in its full colors as the scene is meant to be viewed in a theater. The machines create the frame, and it is then captured as one of thousands of frames in the movie. When you watch the movie, you see anywhere from 24 to 60 frames per second.

All told, it took more than 100 million CPU hours to render the film in its final form. If you used one CPU to do the job, it would have taken about 10,000 years to finish. With all of those CPUs that Pixar did have, it took a couple of years to render.

All of this rendering takes place in a relatively small data center that is cooled by water from the San Francisco Bay, said Estes.

The reason it took so much more computing power is that the eyes of the audience have grown. Something that looked spectacular 12 years ago, like the fur on the monster Sully, doesn’t look so great today. In his final form, Sully had 5.5 million individual hairs in his fur, compared to a fifth of that in the original film. In Monsters, Inc., it was impressive to create one simulated garment with realistic, cloth-like behavior: the shirt on the character Boo. The new film had 127 simulated garments, and the hair and cloth simulator had to be re-coded from scratch.

The tools that the technologists have built for the artists and animators are aimed at making it easier to make creative decisions. They use tools like a storyboarding animation system to take a system that once existed only on paper — comic-book-like storyboards — and turn it into a real-time visualization tool. Van Gelder said the artists and storytellers created scenes with animated stick figures to map out a scene that would be fleshed out later. The storyboarding tools can run at the fastest speeds because they leave out a lot of details.

With storyboarding, the artists set up background objects, pose the characters, and slowly add details with each creative pass. The GPU-based workstations render the results in real time. These technologies save many hours of work, but they also allow the artists do a lot more than they have ever done before, Estes said.

Once the storyboards are approved, the artists take another run at building a more complicated scene with real 3D models of the characters and objects. That is hard to do since Sully himself had so many hairs on him, each with four points of data.