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Inertial rotation on a parented layer
Hi, a couple of years ago I came across this expression, here on these forums, that adds inertial rotation to a child layer based on the position of its parent. It works great, but has a few limitations that I have been trying to figure out how to fix, but I am just not experienced enough with expressions. The limitation is that it only works when the parent layer moves on the X axis. I am wondering if there is a way to make it work on the Y axis as well….and maybe even be affected by the parent layers rotation? If someone wants to take a look, I would appreciate it very much! thanks!
n = 0;
amp = .04;
freq = 2.0;
decay = 3.0;ppos=thisLayer.parent.transform.position;
parv=clamp(ppos.velocity[0]*amp,-90,90)
if (ppos.numKeys > 0){
n = ppos.nearestKey(time).index;
if (ppos.key(n).time > time){
n--;
}
}
if (n == 0){
ppos.velocity[0]
t = 100;
}else{
t = time - ppos.key(n).time;
}if (n > 0){
v = ppos.velocityAtTime(ppos.key(n).time - thisComp.frameDuration/10)*-1;parv + v[0]*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
}else{
parv
} -
3 Replies
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Yes, that’s pretty simple.
First of all, the line
ppos.velocity[0]is unnecessary, you can delete it.The code works on separated dimensions, so for Y you need to change the two remaining [0] values to [1].
(If you needed Z values, you’d put [2] there.)
For rotation, you just delete both [0] and replace the line
ppos=thisLayer.parent.transform.position;with
ppos=thisLayer.parent.transform.rotation;Kalleheikki Kannisto
Senior Graphic Designer -
amazing! thanks for the response! So I know there is a way for this to work on several axis now. In my original post I was actually wondering if there would be a way for this expression to allow inertia on X and Y simultaneously, maybe with a slight tweak so that inertial movement on Y is slightly “muted”, but your post puts me alittle closer to that. Thanks.
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Yes, just use them on separated Y and Y axis, and you can tweak different settings for both, since it’s two separate expressions.
Kalleheikki Kannisto
Senior Graphic Designer
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