AE Tips 004: Inertial Bounce

最近學到一個不錯用的AE expression, 跟據物件目前時間的速率去產生出慣性的離心力量與反彈力量. 語法如下:

// Inertial Bounce (moves settle into place after bouncing around a little)
n = 0;
if (numKeys > 0){
n = nearestKey(time).index;
if (key(n).time > time){
n--;
}
}
if (n == 0){
t = 0;
}else{
t = time - key(n).time;
}

if (n > 0){
v = velocityAtTime(key(n).time - thisComp.frameDuration/10);
amp = .08;
freq = 2.0;
decay = 3.0;
value + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
}else{
value;
}

建議套用在position上, 調整語法裡面的amp/ freq/ decay去控制影響力!
AE CS3 sample file here!!