elastic and bounce expressions

[Filip Vandueren]

The basic formula for 2d position springiness is this:

inertia = 0.95;
k= 0.10;

start=position;
will=[0,0];

for (j=0; j<=time; j+=thisComp.frameDuration) { target=thisComp.layer("ball 2").position.valueAtTime(j); diff = (target-start); will = [will[0]*inertia + diff[0]*k , will[1]*inertia + diff[1]*k] start += will; } start; Dan has a different one on his site, that allows for having the spring to have a certain length when rested: https://www.motionscript.com/design-guide/elastic.html

[Thomas Passow]

Thanks Filip! by splitting my layer, I was able to get the action of the bounce to look quite good with your expression.

[Andy Engelkemier]

I was looking for this, but I knew there was something I was missing. Although this post works, this might be a little better if it works for your use (I know this is old, but it might help people like myself find what they need):

https://www.motion-graphics-exchange.com/after-effects/Wiggle-rubber-bounce-throw-inertia-expressions/4ad0f32a944ad

The script stops analyzing all previous frames once the bounce stops.

Here’s the code (apply it directly to the layer you’re animation).
// 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 = .05;
freq = 4.0;
decay = 2.0;
value + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
}else{
value;
}