[John Gardner]

Hi Jim,

Did you ever find a solution to your question? I happen to be looking for a similar expression, so I’m curious if you found anything.

Thanks,
John

[John Gardner]

Hi John,

In case you need additional reference… I hacked together this solution as well… My apologies for not providing credits, as I pulled info from many people, so its a bit like making Frankenstein…

Anyway, I would like to figure out how to add in some anticipation to the Skew value, just before the 1st key frame, so the shape layer sort of flexes before it moves.

Place the following expression at: Shape layer > Content > Transform > Skew

freq = 5;
decay = 5;
p=transform.position;
x=transform.position[0];
n = 0;

if (p.numKeys > 0){
n =p.nearestKey(time).index;
if (p.key(n).time > time) n–;
}
if (n > 0){
t = time – p.key(n).time;
amp = p.velocityAtTime(p.key(n).time – .001);
w = freq*Math.PI*2;
result = amp*(Math.sin(t*w)/Math.exp(decay*t)/w);
x=result[0];
}else
n;

[John Gardner]

Thanks, John!