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Center of gravity - Keep your character in balance!

Updated: Feb 1



Is Sandra Bullock in balance?

Character balance, center of gravity

Wait.. Does she have two left hands? Ok that's not the question...


How can you be sure your character is in balance? Let's find out... And it all starts with the center of gravity...


Here is what we are covering:

  • What is the Center of gravity?

  • What is balance?

  • What is the base of support?

  • What about human characters?

  • COG fun facts.



1 - What is the Center Of Gravity (COG)?

It's two important things!

Gravity movie
Gravity movie
  • It is the point where your mass is concentrated

  • it is the center of rotation of an object (or Sandra Bullock)


2 -What is balance?

It is when an object or a character can stand still without falling.


balanced building
  • The building is well balanced.

  • The building is not balanced, it falls.

uncertain balance
  • What about this one?


Let's find out.


First, let's find the Center of gravity (COG) of this building. Its shape is simple, it's made of concrete only. Well the COG will be right in the center here:

building COG


3 - What is the Base of support

The base of support is the area of contact between an object and its support .

Building COG and Base of support

And now the golden rule: For an object to be balanced, the center of gravity must be over its base of support.

Building falling

How does a base of support look like ?


3d building base of support

In this case, it is quite simple. The base of support is this green square, which is the same shape as the building.


  • What about a fancy object like a tripod?

tripod contact

Individually, each pod has a base of surface like those red dots. But as one main object, the base of surface is this:

Tripod base of support

So, while the COG is over the base of support, the tripod won't fall.

tripod balanced unbalanced


4 - What about humans ?

Where is the human's Center of Gravity?

Humans COG

Men's COG is usually on the chest's center.

Women's COG will mostly be around the belly button. Why don't we have the same COG? Women's legs are usually longer than men's. Their hips also are generally larger while mens have larger chests.

Keep in ming each body is different, this is a general tendance, not a universal truth. Take time to observe your design and figure out the logical COG position.

This is why you can see all a fuzz around the "Center of gravity challenge" on youtube.


What is the base of support for humans?

Feet base of support
High Heels, base of support
Grampa base of support

You got it. While the COG is over the green base of support your character will be balanced.


5 - COG Fun Facts


The COG can be outside an object!

Fancy COG

The COG is not alway in the center.

Axe COG

The COG can move

Indeed if the object change his shape, the COG will move accordingly.

Let's take the example of a character doing a backflip.

Backflip COG
https://www.youtube.com/watch?v=51Gc_KbNLFI

As the character is straight, the COG is situated in his chest.

When the character is packed with bend legs, the COG moves somewhere between legs and chest. You can see how the COG is the center of rotation. So if you have to animate a backflip with 3d animation, remember to animate your pivot point. By the way, did you notice how this COG act like a bouncing ball?.


Now you have a better understanding of the physics behind the center of gravity and balance; your next walk cycle will look better...

Balanced Walk


So, is Sandra Bullock in balance?

Unbalanced Character

Not quite! Almost there Sandra, move a bit to your left... Bring your right foot in...

Balanced Character

That's better!

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