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Arts & Entertainment

The physics and physicist behind the hit game Angry Birds

Screenshot of the Angry Birds game.
Screenshot of the Angry Birds game.

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There seems to be no stopping the Angry Birds.

The game was released in 2009 – and since then, gamers have bought hundreds of millions of copies. The characters are on T-shirts, toys and there’s even talk of an Angry Birds movie.

And while the plot of the game isn’t too realistic –- irate birds flinging themselves at green pigs -- the game’s physics are very real. The two-dimensional world of Angry Birds uses the same Newtonian laws that govern how things move in our 3-D world.

KPCC’s Sanden Totten has this look at the physicist behind this and other popular video games.

Meet Erin Catto. He lives in Irvine. He’s a father of two, a video game fan and a Cornell graduate who holds a PhD in Theoretical and Applied Mechanics. He is also responsible for the physics of Angry Birds: he created a program applying Newtonian Laws to gameplay. It’s called Box 2D.

“This is what I call the Box 2D mothership over here," Catti says, indicating toward a computer where, with a few quick keystrokes, he calls up a virtual world in which he is the master of gravity, friction, momentum.

“I’ve always been interested in the way things move in the real world that we see, like, why does it move like that? Why does it slide like that? And why does it tumble? So I have always wanted to explore that and recreate that.”

You can apply the Box 2D code to any video game to give it real world physics in two dimensions. Sounds like an obvious feature, but let’s take a quick trip back through video game history.

In the early days, games were full of flimsy physics. Just think of Super Mario. “Mario can stop in a dime. He can do a 180. He can actually change his direction in the air. But you know if you jump, you can’t reverse and go backwards.”

It wasn’t that programmers didn’t know how to code physics; some of the earliest games were physics heavy. But as companies mass-produced consoles, things changed.

Stanford University game historian Henry Lowood explains, “I think what happened was that because of the processing power of the early consoles and such, they couldn’t really do everything.”

Lowood says programmers often traded physical rules for better graphics and longer play. But as machines got faster and more powerful a decade ago, Lowood says game developers tried for a different experience.

“You just see a desire to constantly to improve the immersion factors for those games. Which means making them more realistic to a lot of people. That means photo-realism and other things. And I think for some people that would also include physics.”

Around that time, companies started hiring physicists to help the action feel real. For a math-obsessed PhD gamer like Erin Catto it was a perfect fit.

“So I just had to find my way to wiggle myself into that industry," he says. Sure enough he did, eventually working on Tomb Raider, World of Warcraft and other hugely popular games.

Catto developed Box 2D in his spare time to teach programmers about coding the laws of physics. The code was so basic, he gave it out for free on the Internet. That was in 2006. In 2007 – smart phones hit stores – and developers were eager to tap that new market.

“What happened was people got this code, they went off and tried to make games with it. People started downloading it like crazy and it kinda spawned a new genre of game.”

Crayon Physics, Bike Baron, iBlast Moki all used modified versions of the free Box 2D physics code. Then there was a tiny game company out of Finland.

The rest is touch screen history. By some estimates, Rovio, the company behind Angry Birds, is worth over a billion dollars. Erin Catto? He’s never made a dime for his contribution.

“Almost everyone says ‘Jeez, Erin, you could have your own island now if you just charged for Box 2D!’ The ironic thing about that is then I wonder what if Angry Birds used something else because I was gonna charge for it? Well, maybe if they used something else that wasn’t as good, maybe Angry Birds wouldn’t have succeeded. And I’m just happy that everyone is enjoying the games.”

Besides, Catto says, he’s doing well. He has his dream job, adding gravity, velocity and mass to video games for Blizzard Entertainment.

And Rovio lists him and Box 2D in the Angry Birds credits. Oh yeah: Erin Catto did get a free Angry Birds hoodie.

“I have the sweatshirt but actually I have never worn it because it’s red. I generally don’t wear red. That’s a silly reason. If they would send me a blue one I would wear it!”

The birds are angry, but this physicist says he has no hard feelings.