Modifying the values of properties using Expression Controls effects

Use Expression Controls effects to manipulate one or many properties' values in your expressions. These effects provide controls that you can refer to in any expression. A single control can affect several properties at once. You can apply Expression Controls effects to any layer; however, it is useful to apply them to a null layer, which you can simply use as a control layer. You then add expressions to other layers to access that control--you can simply copy and paste the same expression on different layer properties. For example, you can add the Slider effect to a null layer (Null 1), and then copy and paste an expression such as the following to a series of layers in the composition:

position+[0,10*(index-1)*thisComp.layer("Null 1").effect("Slider Control")("Slider")]

Each of the layers with this expression will animate by a 10-pixel difference (10*(index -1)) returns the layer number - 1, times 10, as the starting position value) and uses that as you drag the slider. All you need to do is set keyframes for the slider on the null layer and all the other layers animate accordingly. (For information on applying effects, see Applying and controlling effects.)

To apply Expression Controls

In the Timeline window, select the layer to which you want to add the expression control and choose Effect > Expression Controls > [effect name].

After Effects includes the following Expression Control effects for which you can set keyframes:

Angle Control

This control contains a dial that rotates from 0 to 360 and adds rotations. You can adjust the angle control by dragging the dial or dragging the underlined values.

Checkbox Control

This control contains a single checkbox that you can click. You can animate this control to start and stop animation at specific intervals.

Color Control

This control contains a color swatch and an eyedropper. You can use this effect to control the gradual or sporadic change of colors on one layer or among several layers.

Layer Control

This control contains a layer menu that lists all of the layers in the active composition. You cannot add keyframes to this effect.

Point Control

This control contains an effect point control. You can use this to perform as a master control for animation in a series of layers.

Slider Control

This control contains a slider with a default value range of 0 to 100. To use values that exceed this limit, drag the underlined value above the slider instead. To change the slider range, right-click (Windows) or Control-click (Mac OS) the underlined slider value and choose Edit Value from the menu that appears. Type the new values in the Slider Range text box.