Using expression controls effects, Convert an expression to keyframes – Adobe After Effects CS3 User Manual
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AFTER EFFECTS CS3
User Guide
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Note: As with pasting keyframes and other items, you can often paste the item into the target layer and rely on After
Effects to determine which property should be the target of the paste operation. For example, this works for copying
Position properties from one layer to another, but you must select the target property yourself if you are pasting an
expression from a Position property into a Scale property.
See also
“Save an animation preset” on page 353
“Work with layer properties in the Timeline panel” on page 152
Using Expression Controls effects
Use Expression Controls effects to add a control that you can use to manipulate one or many properties’ values by
linking the property to the control using expressions. 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 controlling layer. You then add expressions to properties on other layers to take input from that
control.
For example, you can add the Slider Control effect to a null layer (Null 1), and then apply this expression to the
Position properties of multiple layers:
position+[0,10*(index-1)*thisComp.layer("Null 1").effect("Slider Control")("Slider")]
In this example, as you drag the slider, each layer with this expression will move. The layers with greater index
numbers (layers toward the bottom in the Timeline panel) will be shifted more than the layers with lower index
numbers, at 10-pixel intervals. You can set keyframes for the slider on the null layer, and all of the other layers will
animate accordingly.
You apply Expression Controls effects to a layer in the same ways that you apply other effects, such as dragging the
effect onto the layer from the Effects & Presets panel.
To modify the range of a control, right-click (Windows) or Control-click (Mac OS) the control’s underlined property
value and choose Edit Value from the context menu.
Harry Frank shows how to use an Expression Controls effect (the Slider Control effect) as part of his video tutorial
about converting from RGB to HSL using expressions:
.
See also
“Create a null object” on page 159
“Apply an effect or animation preset” on page 351
Convert an expression to keyframes
In some situations, it may be useful to convert an expression to keyframes. For example, if you want to freeze the
values in an expression, you can convert the expression to keyframes and then adjust the keyframes accordingly; or,
if an expression takes a long time to evaluate, you can convert it to keyframes so that it renders more quickly. When
you convert an expression to keyframes, After Effects evaluates the expression, creating a keyframe at every frame,
and then disables the expression.
❖
In the Timeline panel, select the property on which the expression is written and choose Animation > Keyframe
Assistant > Convert Expression To Keyframes.