ANIMATION BOOTCAMPEXPRESSIONS STARTER KIT

Sometimes you CAN let the computer do the work.

Adding an Expression to a Property

time

Other Expressions Resources

loopOut(option) - options are “cycle” | “pingpong” |

wiggle(frequency, amount)

.toWorld([0,0]) - note, the [0,0] can be any coordinate, 2D or 3D

linear(value, minIn, maxIn, minOut, maxOut)

Expressions can replace or work in tandem with keyframes. You add the Expression to the PROPERTY that you’d like to be able to control. The easiest way to do this is to OPTION-CLICK (or ALT-CLICK) the Stopwatch icon next to that property. This enables Expressions and opens the Expression Editor.

The “time” expression returns the current time in SECONDS. So at 1-second, the value of “time” is 1. At 30 seconds, the value of “time” is 30. If you want a property to increase at a constant rate, multiply “time” by some number.

motionscript.comDan Ebbert’s is the OG of After Effects Expressions, and his site is a goldmine of knowledge for beginners and experienced Expressioneers alike.

Expression BasicsThis is Adobe’s site that actually has a pretty good run down of the basics of Expressions. You’ll learn as much (or as little) as you want to.

Expression Language ReferenceAnother Adobe page that lists every single Expression you can use inside of After Effects, including brand new ones that have been added in CC2014. Bookmark this.

This loops any existing keyframes using the option you specify. loopOut(“cycle”) will repeat a sequence of keyframes. loopOut(“pingpong”) will oscillate back and forth between the beginning and end of an animation. loopOut(“continue”) will maintain the final velocity of the last keyframe. This Expression is very useful when combined with Time Remapping, allowing you to loop complex animations indefinitely.

The wiggle Expression will add randomness to any existing value (or even keyframed values) based on the Frequency and Amount you specify. Frequency refers to the number of times PER SECOND the value will change, and Amount refers to the absolute CHANGE in the value that will be allowed to happen.

This will convert the RELATIVE postion of a layer (for example, one that is parented to something that is already moving) into ABSOLUTE coordinates. Watch the video, it will explain that better than this PDF. ***This expression references a LAYER, not a PROPERTY!!!

This expression takes a value (which could come from an Expression Control Effect, a layer’s property, etc..) and remaps it based on the numbers you feed it. For example, you could look at a Slider Control that goes from 0 to 100, and map the output of those values to something more specific, like -20 to 37. Watch the video... this one is hard to explain, ha!

Ninja-Level After Effects artists often use Expressions to make certain times of animation easier, more flexible, and frankly POSSIBLE. There are times when animating some complex, interlocking set of layers will be so tedious that you’re better off creating a little rig that can do the grunt work for you.

Expressions are a bit like programming, so it can take some time to get used to how they work. But it’s worth it if you want to really tap into the full power of After Effects. Here are some simple expressions and resources to get started.

Note that the “.toWorld” expression is tied to the LAYER called “EndRef” and not the POSITION PROPERTY on that layer.