What it does
The Expression modifier sits in a layer's modifier stack (with Wiggle, Set Driver/Driven and Linear). Its result replaces — or combines with — the value of the property it drives. Expressions run after Drivers, in preview, export and Frame Rate holds.
How to use it
- Select the layer and add a modifier (+ Modifier), choosing Expression, or switch an existing modifier's kind menu to Expression.
- Under drives, pick the target layer and property.
- Type the expression in the text box. It starts as
value(the property unchanged). - Press ⌘↩ (Ctrl+Enter) or click away to apply. Esc puts back the last applied text.
- If it has an error, the box turns red and the message shows underneath, e.g.
Line 2, column 5: unknown name "wigle".
Scripts can set one too: prop.expression = "wiggle(2, 30)".
Options
| Name | What it does | Default/range |
|---|---|---|
| Enable dot | Turns the modifier on or off. | On |
| Kind | Wiggle, Set Driver/Driven, Linear or Expression. | Expression |
| drives | The layer and property the expression writes. | — |
| Combine | How the result meets the property's value: override, add, subtract, multiply, blend. | override |
| Influence | How much of the result is applied. | 100% |
| Expression text | The expression. | value |
| × | Removes the modifier. | — |
What expressions can drive
Position (whole, X or Y), Scale (whole, X or Y), Anchor Point (whole, X or Y), Rotation, Opacity, the shape and text values Drivers can reach, and effect parameters.
Shortcuts
| Action | Mac | Windows/Linux |
|---|---|---|
| Apply the expression | ⌘↩ | Ctrl+Enter |
| Cancel the edit | Esc | Esc |
While the box has focus, typing doesn't trigger app shortcuts (Space doesn't play).
Tips
- macOS smart quotes (“ ” ‘ ’) are read as plain quotes.
valueAtTime(t)andloopOut()read the keyframed value before modifiers, as AE does.