We Talked to a Scientist Who Makes Those Incredibly Satisfying Computer Animations

Physics-based animation can be used to test the strength of bridges, make hyper-real animated films, and blow your mind.

Christopher Batty’s job is to make super satisfying animations like these—all day, every day. But you won’t see “artist” or even “graphic designer” printed on his business card. Batty is a professor of computer science at the University of Waterloo in Ontario, Canada, and the animations he makes aren’t to appease the ASMR contingents on YouTube.

Mostly his animations form the basis of special effects in films, but they have wider scientific appeal: Batty’s techniques are also used to to view or measure phenomena that either don’t exist on Earth or are too dangerous in real life. Think, how a bridge might react to strong winds, or how building a dam could alter river flows.


Image: Fang Da, Christopher Batty, Chris Wojtan, Eitan Grinspun

Batty tells me how a particular method for simulating bubbles he wrote with colleagues from Columbia is now being used to model how an embryo develops in the womb, based on the gravitational or chemical forces it experiences.

He describes his field of physics-based animation as a “marriage of computer science and physics.” His goal is to come up with a mathematical equation to describe the motion of everyday objects, such as water, hair, clothing, or honey.

Image: Egor Larionov, Christopher Batty, Robert Bridson

Those mathematical equations are then written into computer code, which is incorporated into animation software such as Houdini or AutoDesk’s Maya—the programs behind the blockbusters Moana and Lord of the Rings.

Batty explains it’s like your high school physics class, where you’d write an equation for the coordinates of a bullet flying through the air. But instead of a single object, you’re dealing with hundreds of thousands of moving parts. Imagine the many water droplets that make up a sloshing liquid or the single pieces of hair blowing in the wind. It’s not always possible to get one equation for every individual bit—you have to use computer science to approximate them. That’s where Batty comes in.

Part of the reason to use science, not art, as the basis for animation in film is that audiences demand hyper-realism. A lame explosion here or a botched effect there can lead to ruined viewer experience and, ultimately, poor sales at the box office. (Remember Halle Berry's weird CGI body double in Catwoman? They lost $10 million making that film.)


Image: Ryan Goldade, Christopher Batty, Chris Wojtan

On the other hand, great animation can take your breath away. “I just remember seeing Avatar and being absolutely floored by how beautiful it was,” recalls Ryan Goldade, a PhD student of Batty’s. “What’s really cool about this field is we’re giving people the ability to bring their vision to life in a way they just couldn’t do before.”

Accuracy isn’t always the end goal. For one, viewers find it hard to distinguish between an animation that’s hyper-real and just real enough. Sometimes the physics can be at odds with what an artist wants, so any software needs flexibility built into it. The example Batty gave is when he was tasked with building a character made entirely of tar. “You want the physics to shine but you also want the artist to be present.”

Physicists and engineers are using the same mathematical and computational science techniques as Batty to describe how galaxies form, model nuclear reactions, and test the strength of bridges. With computational physics, “we can turn on or turn off different parts of reality to see if we get the same effects or not,” says Batty.

Models can always be made more detailed or accurate but that ultimately means relying on bigger, faster computers to run the simulation. There is still a lot of room for improvement, Batty says—particularly in getting the same level of detail in computer games as in movies. “We’re nowhere near that kind of level. The sky’s the limit.”

Image: Yonghao Yue, Breannan Smith, Christopher Batty, Changxi Zheng, Eitan Grinspun

Image: Fang Da, David Hahn, Christopher Batty, Chris Wojtan, Eitan Grinspun