Adobe After Effects CS3 - Manual (Page 590)

AFTER EFFECTS CS3
User Guide
585
Example: Animate scale at each layer-time marker
❖ Apply the following expression to a Scale property to make a layer wobble at each marker:
n = 0;
t = 0;
if (marker.numKeys > 0){
n = marker.nearestKey(time).index;
if (marker.key(n).time > time) n--;
}
if (n > 0) t = time - marker.key(n).time;
amp = 15;
freq = 5;
decay = 3.0;
angle = freq * 2 * Math.PI * t;
scaleFact = (100 + amp * Math.sin(angle) / Math.exp(decay * t)) / 100;
[value[0] * scaleFact, value[1] / scaleFact];
See also
“Add, edit, and remove expressions” on page 549
Example: Start or stop wiggle at specific time
You can use any expression in place of the wiggle expression used here, to begin and end any expression’s influence
at a specific time.
• Apply the following expression to a property to wiggle it beginning at time 2 seconds:
timeToStart = 2;
if (time > timeToStart){
wiggle(3,25);
}else{
value;
}
• Apply the following expression to a property to stop wiggling it at time 4 seconds:
timeToStop = 4;
if (time > timeToStop){
value;
}else{
wiggle(3,25);
}
• Apply the following expression to a property to start wiggling it at time 2 seconds and stop wiggling it at time 4
seconds:
timeToStart = 2;
timeToStop = 4;
if ((time > timeToStart) && (time < timeToStop)){
wiggle(3,25);
}else{
value;
}