Pixar Animators Use GPUs to Create a Singing Volcano

by Tony Kontzer

Creating singing volcanoes isn’t, perhaps, a common use case for NVIDIA products.

But in a packed session at the GPU Technology Conference, attendees learned that GPUs helped Pixar get the details right in animating Uku, the singing volcano in the soon-to-be-released short film Lava.

Animating a quarter-mile-tall rock is different than animating people and animals. For instance, Pixar wanted to be sure Uku moved like trembling rock. And when animators depicted the volcano’s mouth moving, Presto — Pixar’s proprietary GPU-powered animation system — helped the production team determine that Uku’s “cheeks” were moving too much.

“We got comments that it looked less like a rock and more like a guy in a rock suit,” said Byron Bashforth, the film’s technical director.

The discovery prevented an unnecessary delay while the segment went to rendering, where it might have been discovered in the past. And quite often, Pixar’s animators are able to unearth more obvious flaws on their own rather than relying on the shading team to alert them.

Presto — which Pixar’s engineering lead, Dirk Van Gelder, demoed in a keynote at GTC 2014 — is a powerful application that helps animators see their work with and without shading, by simply using a drop-down menu.

While the cheek movement was a subtle and unexpected discovery, Presto users are able to view other cause-and-effect scenarios in real time.

For instance, the production team wanted Uku’s eyes to close when clouds shadowed his face to emphasize sadness. To achieve this before the addition of realistic cloud shadowing, Van Gelder said his team developed a light blocker that enabled them to simulate shadows closing over Uku in real time.

That, in turn, allowed animators to ensure that the character’s eyes shut in sync with shadows hitting his face.

It’s All in the Eyebrows

The animators also were able to use Presto’s real-time capabilities to avoid an issue with Uku’s rock-hewn “eyebrows.”

When animators viewed the raw animation of Uku’s moving face without lighting, texture or shading, the eyebrows seemed to move too much.

But when shading was added using a drop-down selection, the eyebrows seemed to move too little.

In the past that change would have been made after the rendering process. And that would have caused more delays.

“Rendering is getting more and more expensive,” said Van Gelder. “The more we can show them in Presto, the more we can hold off rendering until later in process.”