Expression controllers are where expressions and effects collide. Here’s how to use them in After Effects.
There are a lot of reasons why you may want to use an expression controller in After Effects. They can save you time by manipulating values across multiple layers and effects with a single slider. They can turn layers on and off. They can even make your project easier for others to manipulate.
However, expression controllers aren’t self explanatory. Each individual expression controller requires at least one additional step to make them work in After Effects. Let’s take a look at every expression controller in After Effects and give a few examples for when you may want to use a given expression controller.
Setting Up an Expression Controller
While an expression controller can be easily applied to any layer (just drag and drop), it’s a best practice to create a dummy layer where all of your dummy layers will be found. So before you do anything, create a new adjustment layer (option+command+Y) and give it an appropriate name. Here at RocketStock, we always label our expression controller as ‘Scene Options,’ but you can simply use whatever makes sense for your composition.
All of the expression controllers listed below will require pickwhipping in order to work. However, you will need to lock your ‘Scene Options’ effects panel by simply hitting the lock icon next to ‘Effect Controls.’
3D Point Control
3D Point Control allows you to connect the 3D position of a layer or parameter to a slider. This can make it easy to attach multiple layers to a single point in 3D space.
Using 3D Point Control
Pickwhip a 3D point parameter to the 3D Point Control expression controller.
3D Point Control works very similarly to the Point Control expression controller. All you need to do is (option+click) on the stopwatch next to the parameter that you need to attach to the 3D point control. Once you option click, you will see a little swirly logo. Simply click and drag the swirly logo to the 3D Point Control expression controller. This process is called pickwhipping and it will link your 3D parameter to the location of the 3D point control.
If you have a parameter that needs to be limited to 360 degrees, like rotation, Angle Control is perfect for you. This is especially true if you want to easily attach multiple layers to the same rotation parameter.
Using Angle Control
Pickwhip a rotation parameter to the Angle Control expression controller.
Angle Control can be easily adjusted by simply pickwhipping a rotation or angle parameter to the Angle Control expression controller. Simply (option+click) on the stopwatch next to the rotation parameter you wish to attach to the Angle Control expression controller. You will see a swirlly logo. Grab the swirlly logo and drag it to the Angle Control effect in the effects panel. You may need to lock the effects panel to a certain layer if you are attaching the rotation to a different layer. After you attach your rotation to the Angle Control, you will immediately be able to adjust the angle using the Angle Control.
A Checkbox Control is perfect if you have scene options in your composition. For example, you could set up a Checkbox Control whether or not an audience sees a certain layer. We use Checkbox Control expressions all the time to turn layer opacity on or off in our custom After Effects templates here on RocketStock.
Using a Checkbox Control
A Checkbox Control works a lot like a true or false statement: 0 if false and 1 if true. So in the case of your scene, a “0” will represent a checkbox not selected, and a “1” will be a checkbox selected.
The Checkbox Control cannot simply be pickwhipped to the expression controller. You need to take it one step further. In order to use the Checkbox Control you will need to use the small expression:
if (“PICKWHIP TO CHECKBOX” ==0) 0 else 100;
A checkbox can only control two values. For example, you could use the checkbox to control the opacity of a layer from 0% to 100% — effectively making it entirely visible or invisible with a single click of the mouse. To use the checkbox control, you can option click on the stopwatch next to the parameter in which you want your checkbox to be attached.
You will then type in the expression listed above. However, depending on the values of the checkbox, your numbers may be different than 0 and 100. Just remember: the first number after the parenthesis is the value of the checkbox unchecked. The value after ‘else’ is the checked value.
A Color Control allows you to attach a color parameter to a color expression controller. This is great if you have a lot of different colored objects in your scene. In a nutshell, a Color Control will allow you to change the colors of multiple layers with a single color control. Pretty handy, right?
Using a Color Control
Pickwhip a color box to the Color Control expression controller.
To use a Color Control, all need to do is (option+click) next to a color effect parameter stopwatch in the timeline. This will reveal a small swirly logo. Simply drag the small swirly logo to your Color Control expression controller effect. You should now be able to adjust the color using the color control.
This video from kewlhappens shows us how to use expression controllers to manipulate universal project colors in After Effects.
The Layer Control expression is probably the most difficult to use in After Effects. It’s really a tool for intermediate to advanced expression users. The Layer Control essentially recalls one of the layers in your composition. This can be important if you are trying to designate which layer gets certain transform properties in your timeline.
Using Layer Control
Pickwhip your desired property to the Layer Control expression controller.
Most people use a Layer Control in conjunction with a variable. For example, most people will define a variable like “x” with the layer control. This will result in the “x” variable having the value of whatever layer your Layer Control expression is set to.
This video tutorial from Mikey Borup does a great job at explaining what layer controls can do.
A Point control works exactly like a 3D Point Control, expect a Point Control is missing a third z-space value. A Point Control is perfect for moving objects in 2D space.
Using a Point Control
Pickwhip a 2D point to the Point Control expression controller.
To use a Point Control, all you need to do is (option+click) on the stopwatch next to a 2D point value in the timeline. You should now see a swirly logo. Drag the swirly logo to the Point Control expression control effect. Your clip should now be attached and easily moved using the Point Control effect.
A Slider Control is a great way to set a value in After Effects. For example, you could easily attach the opacity of a layer to a Slider Control so users of your After Effects project file could designate how opaque a given layer should be. Sliders can adjust much more than opacity though. You could easily attach single value positions, transform properties, and effect intensities using a slider effect.
Using the Slider Control
Pickwhip a value parameter to the Slider Control expression controller.
To use a Slider Control, simply (option+click) on the parameter which you want to attach in the timeline. You should now see a swirly logo. Simply drag the swirly logo to your Slider Control expression controller effect. Your parameter value will now be attached to the slider control.
It should be noted that you can easily set the minimum and maximum Slider Control by right-clicking the slider in the effects panel and selecting ‘Set Value.’ From there you can easily adjust the minimum and maximum value of your slider.
This video from RiverCityGraphix shows us how to use a Slider Control with a wiggle expression to control wiggle amplitude. This is very handy. I use this technique all the time.