YUNOVA · After Effects
Module 13: Advanced expressions
if/else conditions in expressions
Key points
- Expressions use JavaScript if/else syntax to choose a value.
- A condition can test time, a slider value or another layer's property.
- The last evaluated line of the expression becomes the property value.
valueAtTime and delayed animation
Key points
- valueAtTime(t) reads a property's value at another time.
- Subtracting a delay from time makes a layer follow another with a lag.
- Using the layer index in the delay staggers many copies automatically.
Source text expressions
Key points
- Source Text expressions can set text from other layers or values.
- Math.round or toFixed tidies numbers shown as text.
- Counters and live dates are common uses of Source Text expressions.
Time remapping
Key points
- Time remapping adds keyframes that control which frame plays when.
- It can slow down, speed up, freeze or reverse a clip.
- Enabling frame blending keeps remapped slow motion smoother.
Building a reusable expression rig
Key points
- Expression controls (sliders, checkboxes) give a rig simple inputs.
- Linking properties to one control layer lets you change many at once.
- A rig can be saved as an animation preset or a template to reuse.