4 Replies Latest reply on Oct 7, 2016 12:57 PM by tiagoBRcastro

# How to simulate gravity acceleration animation (free fall) in After Effects.

Hello,

I want to make men falling from the sky. That meens that they don't have to fall with the same speed but they have to be accelerating in order to simulate gravity drop. They have to accelerate by "G" (9,81m/s)2.

How can I achieve this accelerated animation by just manipulating the keyframes?

Or, what is a very simple expression which includes G acceleration (9,81)?

I don't like expressions, so it has to be an extremely short, simple and very effective one.

Thanks

• ###### 1. Re: How to simulate gravity acceleration animation (free fall) in After Effects.

As simple expression would be like this:

seedRandom(index,true)

mGravBase=9.81; //basic gravity

mGravVar=random(-1,1); //gravity variation

mAccel=time*(mGravBase+mGravVar);

X=value[0];

Y=value[1]+Math.pow(mAccel,2);

[X,Y]

This will make a layer drop straight down from its start position. And when you duplicate it, there wil lbe slight variations based on teh random parameter. More fancies could of course be added...

Mylenium

• ###### 2. Re: How to simulate gravity acceleration animation (free fall) in After Effects.

You could also do this by simply manipulating the curve in the graph editor. Select separate dimensions and animate y as shown:

Since there are no feet and inches in AE being absolutely accurate to the real world is purely subjective. In this case I've just created an approximately parabolic curve by stretching out the handle on the first y keyframe speed graph and then moving the second handle next to the second keyframe and positioning it to the top of the curve.

If your object is going to hit the ground then you'll also need some kind of bounce or deformation. Again, this is completely subjective but if you type in realistic bounce expression or bounce expression in the Search After Effects Help field at the top right corner of AE you'll be directed to this series of great expressions by Dan Ebberts.

I would strongly suggest that you try out these expressions and then save each of them to an animation preset so you can apply them to any layer with a single click. It will save you a bunch of time.