To Modify Properties With Expression Controls Effects; Expression Controls Effects; To View Expressions; Working With Expressions - Adobe AFTER EFFECTS 7.0 Manual

To modify properties with 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:
p osition+[0,10*(index-1)*t hisC omp.layer("Nu l l 1").ef fec t("Slider C ont rol")("Slider")]
As you drag the slider, each layer with this expression will animate, with the position of each dependent on the value
of slider and the index of the layer. The layers with greater index numbers will be shifted more than the layers with
lower index numbers, at 10-pixel intervals.
All you need to do is set keyframes for the slider on the null layer and all the other layers animate accordingly.
❖
In the Timeline panel, select the layer to which you want to add the expression control, and then choose Effect >
Expression Controls > [effect name].
See also
"To create a null object" on page 209

Expression Controls effects

After Effects includes the following Expression Controls effects for which you can set keyframes:
You can adjust the angle control by dragging the underlined values.
Angle Control
This control contains a single on/off value that you can click. You can animate this control to start
Checkbox Control
and stop animation at specific intervals.
This control contains a color swatch and an eyedropper. You can use this effect to control the gradual
Color Control
or sporadic change of colors on one layer or among several layers.
This control contains a layer menu that lists all of the layers in the active composition. You cannot add
Layer Control
keyframes to this effect.
This control contains an effect point control. You can use this to perform as a master control for
Point Control
animation in a series of layers.
This control contains a slider with a default value range of 0 to 100. To use values that exceed this
Slider Control
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.

Working with expressions

To view expressions

In Graph Editor mode, the single expression field shows only the expression for the selected property. To see multiple
expressions simultaneously, the Timeline panel must be in layer bar mode.
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