Adobe After Effects Expressions and Scripting 1 — Questions and Answers
Question 1: How do you add an expression to a property in After Effects?
- Alt+click (Option+click on Mac) the stopwatch icon of the property (Correct answer)
- Right-click the property and choose Add Expression
- Click the property name and press E
- Drag from the Expression Picker onto the property
Correct answer: Alt+click (Option+click on Mac) the stopwatch icon of the property
Alt+clicking the stopwatch enables expression mode, showing an expression field and disabling regular keyframing for that property.
Question 2: What does the `wiggle()` expression function do in After Effects?
- Creates random oscillation of a property's value over time with controllable frequency and amplitude (Correct answer)
- Applies the Wiggle effect to the layer automatically
- Randomly shuffles the order of keyframes on the property
- Generates a wiggling motion path for the layer's position
Correct answer: Creates random oscillation of a property's value over time with controllable frequency and amplitude
wiggle(frequency, amplitude) adds random variation to a property, with frequency controlling oscillations per second and amplitude controlling the range.
Question 3: What does `thisComp.layer("Layer Name").transform.position` do in an After Effects expression?
- Returns the current position value of a named layer in the same composition (Correct answer)
- Moves the current layer to the position of the named layer
- Links the composition's output position to the named layer
- Reads the position property from a layer in a different composition
Correct answer: Returns the current position value of a named layer in the same composition
This expression references the Position transform property of a specific named layer in the current composition.
Question 4: What does the `time` expression variable represent in After Effects?
- The current time of the composition in seconds at the current frame (Correct answer)
- The total duration of the composition in seconds
- The frame number of the current frame
- The elapsed CPU processing time for the current render
Correct answer: The current time of the composition in seconds at the current frame
The `time` variable returns the composition's current time in seconds (e.g., 2.5 at 2 seconds 15 frames at 30fps).
Question 5: What does `loopOut('cycle')` do in an After Effects expression?
- Repeats the keyframe animation after the last keyframe by cycling back to the first keyframe (Correct answer)
- Loops the layer's timeline after it ends
- Repeats the layer in the composition render queue
- Creates a pre-comp loop of the layer animation
Correct answer: Repeats the keyframe animation after the last keyframe by cycling back to the first keyframe
loopOut('cycle') repeats the segment between the first and last keyframes indefinitely after the last keyframe.
Question 6: What is the Expression Language in After Effects based on?
- JavaScript (specifically the ECMAScript standard) (Correct answer)
- Python scripting syntax
- Lua scripting language
- C++ with simplified syntax
Correct answer: JavaScript (specifically the ECMAScript standard)
After Effects expressions use JavaScript syntax, giving access to math functions, conditionals, and the After Effects object model.
Adobe After Effects Expressions and Scripting 1
How do you add an expression to a property in After Effects?