After Effects Expressions
Animation on steroïds.
Expressions in After Effects have always been blurry for me. I know they exist, I know they're powerful, I know it could save a lot of time and clean complex keyframe filled compositions but… They are hard to learn!
An ever lasting battle
There is very little documentation and the existing one is hard to find or very old. Very often I just don't have the time to dive into expression learning while animating even though it could help the entire project on the long term. So the last time I had to do a complex animation, I took the damn time!
The begining of the end (of keyframes).
Everyone uses expressions whether they know it or not. Most of the time it's a rather transparent process for the animator. For example: when parenting a property to another one, After Effects creates an expression for us.
I know that most animators don't have any kind of development background. However, if Adobe thought it best to let us use expressions, I think we ought to, at least, try.
Like every optimization process, building an expressions knowledge takes time. However, like all optimization process, you will benefit from it afterwards.
Where to learn
I've gathered a list of my favourite learning grounds. Plenty more exist, go get'em!
- Adobe official expression starter guide (FR)
- Adobe official expression basic (EN)
- Adobe forums for expressions
- Creative Cow expressions forums
- Youtube channel about expressions
- All expressions explained
- All expressions explained again
- Nice examples of basic expressions
Real world example
Let's say you need to animate a rather simple counter from 0% to 100%.
- Start by creating a text layer. Define your typographic choices, colours, etc.
- On the effect menu add expression options > slider control
- Alt + Click the Source text property
- Parent the source text to the slider control through the pickwhip.
You should get something like this in the expressions panel:
- Set two keyframes on the slider from 0 to 100. The text should update accordingly.
- By default, After Effects does not round numbers. In the expression panel, wrap your expression with the
Great! We have a working counter. But we wanted a percentage counter. We could add a % glyph in another text layer but let's not.
Math.round(effect("Slider Control")("Slider")) + '%'
And there we go! A fully functioning and customizable counter using a slider controller and expressions.