Interview: Physics for Animators – Alejandro Garcia


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Whether you’re animating something “cartoony” or realistic, having a good understanding of physics can help to place your characters and special effects in a consistent and believable world. In this interview with Alejandro Garcia, professor of physics at San Jose State University and consultant for Dreamworks, we talk about the does and don’ts, common challenges and storytelling devices that we animators can learn from physics, as well as how to get the best out of real life references. For more visit Alejandro’s blog:

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Juan Carlos

Animation doesn’t always need physics. In some cases it does, in others it doesn’t. Cartoons like Looney Tunes, the classic MGM cartoons, classic Disney shorts, even a lot of modern cartoons like Hotel Transylvania and Cloudy With a Chance of Meatballs uses little to NO real world physics. The Coyote running off a cliff and continuing to run in the air is physically impossible. The Genie from Aladdin does everything that is physically impossible. Art Babbitt’s angry walk defies physics. There are many countless examples of how cartoons do not need physics as detailed as Mr Garcia puts it.

However, Mr. Garcia does make some good points, and most of the basic 12 principles of animation use physics. And having a basic understanding or just idea does help make animation look better. But the core of the matter is that animation doesn’t need to be over explained.

The whole point of animation, as Walt Disney said it, “Animation allows us to do the impossible”. In other words, we can do whatever we want in animation.

Juan Carlos

Hello Ferdinand!

Firstly, I agree that there are different approaches to animation. And what really matters is the end result. I teach my students different ways to animate and encourage them to find their own method and style. All I really care about is the final animation and how that looks.

Secondly, I agree that all animation should have some basic understanding of physics. But just that, a basic understanding or rather, common sense physics. It’s good have a knowledge of it and then distort it to make the animation better. But to hinder animation because it doesn’t make real world physical sense is not good. It can hurt the animation. Animation is supposed be free while following the rules of animation not so much the real world.

Yes, I hate when animation, movies, and art is over explained, over analyzed, nit picked to the nth degree. I feel it takes away the creativity and magic of the animation.

As I said before, the basic 12 principles of animation are based on real world physics. But like your example of Hotel Transylvania, the animation was mostly based on the emotional poses that expressed the feeling and thoughts of the characters. The animation was wonderful and fun to watch. And I didn’t need to believe that these characters are living in the real world or that what they are doing is physically impossible.

If an animation leans more towards realism, then yes, real world physics would apply more. But the animation leans more towards the cartoony world, then it doesn’t need so much attention to our real world physics.

Animation does have rules. But rules can be bent and broken. And animation bends and breaks them all the time. But in order to bend and break a rule, you need to fully understand the rules. For example, the Anticipation principle explains how everything in motion needs a precursor movement in the opposite direction before it moves. Anticipation sets up the audience on what the character is going to do before it does it. The wind up, and the pitch. But this same principle then explains that if you break the rule, you can set up a gag. A character is standing between two thugs, the character winds up to punch the thug on the left but then punches the thug on the right instead. It’s a surprise and it’s funny and it broke the physics rule of should have happened.

This is going back to my Art Babbitt angry walk example. Or when the Genie from Aladdin during the, You Never Had a Friend Like Me sequence, bend and contorts, disfigures and distorts and does anything Eric Goldberg wanted. Or when a character pricks himself with a needle and goes rocketing into the air. Or when the Coyote paints a tunnel on the wall, and the Roadrunner actually runs through it, but he can’t. I remember an episode of Tiny Toons that Buster, Babs, and Plucky where crossing a canyon and running in the air. They remembered from their class that as long as they don’t look down, they can remain in the air. Which is what they did to cross the canyon.

Breaking normal, real world physics in cartoons make them fun. The animation still follows rules yes. But don’t forget that there are cartoon laws of physics. *And like in Who Framed Roger Rabbit?, Roger is unable to escape handcuffs for most of a sequence, doing so only at the last moment. When Eddie Valiant asks, exasperated, “Do you mean to tell me you could’ve taken your hand out of that cuff at any time?!” Roger responds: “Not at any time! Only when it was funny!”.

So the real world laws of physics do not apply in animation when something needs to be funny.

We could go back and forth on this for a while. But my main point is, and I’ll Mr. Disney again, “Animation allows us to do the impossible”.

*That was from Wikipedia.


Exaggeration cannot exist on its own. It is, by definition, dependent upon reality through comparison. For instance, you can’t have louder, bigger, or faster without an understanding of what loud, big or fast are.

The fun from real world physics being broken in cartoons comes from the surprise from the expected. These breaks, though, are not complete breaks. They still adhere to the reality of the animation’s world as well as to the real world. For instance, a character may walk on air but how do they walk? They walk as if they were standing on some ground; there’s weight shift, heel-toe foot contacts, and the standard up and down movement of a walk. When the roadrunner runs through a painting of a road on a wall, he runs as if there was an actual road. Roger still squeezes his fingers together while bending and twisting his wrist to slip through the handcuffs, and there’s resistance from the cuffs, despite the exaggerated squashing and stretching that’s taking place. All of those exaggerations still acknowledge and thus adhere to real world physics in one way or another.

You can’t just do anything, for exaggeration is an embellishment of reality. As such, it must acknowledge that before proceeding. As Chuck Jones said, “the coyote is limited, as Bugs is limited, by his anatomy.”

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