spring effect after keyframes

[Dan Ebberts]

Which expression are you using now?

Dan

[Karinov Mouja]

this screen capture shows the expression and the probleme

[Dan Ebberts]

Try this:


freq = 2;
decay = 1;
mult = .05;

if (numKeys > 1 && time > key(2).time){
t = time - key(2).time;
a = velocityAtTime(key(2).time-.01)[0];
d = a*mult*Math.sin(t*freq*Math.PI*2)/Math.exp(t*decay);
value + [d,d]
}else{
value
}


Dan

[Karinov Mouja]

thanks a lot Dan..
this is what I’m looking for 🙂

I’d like to ask you about 2 things:

can you please explain this sentence:
(a = velocityAtTime(key(2).time-.01)[0];) (till now I can’t figure out how “velocity” works :S

why do you put this variable: mult =.05?
(d = a*mult*Math.sin(t*freq*Math.PI*2)/Math.exp(t*decay);)

[Dan Ebberts]

velocityAtTime just picks up the rate at which the scale parameter is changing at the time of the second keyframe. That way, the bounce amplitude is higher for layers that were going faster before they hit the second keyframe.

The multiplier just attenuates the effect to get into a range that looks right. Adjust it to suit your taste. If you take it out (or set it to 1), with a fast scale-up like you have in your example, you’ll get a pretty extreme oscillation.

Dan

[Blai Graell]

Hi Dan.

Is it possible to do the same with keyframes in x,y,z rotation values of a 3d layer? I tried to apply this same expression to the y rotation value but it repports this message:

“Class ‘Number’ has no property ot method named ‘0’ Expression disabled”

One more thing. I’m trying to do the same with position keyframes, but the result is the layer bouncing in a weird 45 degrees diagonal angle.

Thanks in advance.

[Dan Ebberts]

This version should work for rotation or position:

freq = 2;
decay = 1;
mult = .05;

if (numKeys > 1 && time > key(2).time){
t = time – key(2).time;
a = velocityAtTime(key(2).time-.01);
d = a*mult*Math.sin(t*freq*Math.PI*2)/Math.exp(t*decay);
value + d;
}else{
value
}

Dan

[Blai Graell]

Thank you very much, Dan.

Yesterday I was really in a hurry so I had to manage the solution by myself. I found a lot of help in your site and succeeded to type two expressions that worked. I’m really new in expressions and I’m sure there’s a more simple way to achieve the same, but they worked anyway.

For position (3D):

freq = 5;
decay = 5;
mult = .002;

if (numKeys > 1 && time > key(2).time){
t = time – key(2).time;
a = velocityAtTime(key(2).time-.01)[0];
b= velocityAtTime(key(2).time-.01)[1];
c= velocityAtTime(key(2).time-.01)[2];
x= a*mult*Math.cos(t*freq*Math.PI*2)/Math.exp(t*decay);
y = b*mult*Math.cos(t*freq*Math.PI*2)/Math.exp(t*decay);
z = c*mult*Math.cos(t*freq*Math.PI*2)/Math.exp(t*decay);
value + [x,y,z]
}else{
value + [0,1,2]
}

for rotation:

freq = 4;
decay = 1.5;
mult = .08;

if (numKeys > 1 && time > key(2).time){
t = time – key(2).time;
a = velocityAtTime(key(2).time-.01);
d = a*mult*Math.sin(t*freq*Math.PI*2)/Math.exp(t*decay);
value + [d]
}else{
value
}

Thanks again.

[Eric Mc guire]

Awesome!! Thank you very much Dan!!! The last expression you’ve posted works perfectly with 3D layers. I am kind of a beginner in AE, but I don’t understand why they don’t implement this in the software. Wouldn’t it be terrific to control the decay, amp, etc with a slider instead of expressions values? Thanks again Dan!!!! : ))