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Dan Ebbert’s Scale Bounce expression keeps breaking
Hello Creative Cow,
I’ve got a problem with Dan Ebbert’s Scale Bounce expression, you know the one…
k=16; // final scale
a=5; // how quickly the bounce ends
b=20; // how many bounces it’ll do (that is, the bounce speed)
t = time-inPoint;
x=k*(1-Math.exp(-a*t)*Math.cos(b*t));
[x,x]It sometimes works, but quite frequently I get the Expression Disabled message:
After Effects warning: Expression Disabled. Error at line 0 in property ‘Scale’
of layer 27 (‘car’) in comp ‘Part 6’.
invalid numeric result (divide by zero?).I’ve tried my best to tweak the parameters but to no avail, because I’m just guessing really. I’m wondering if it’s something to do with changing the values of a or b, which i do sometimes. But it shouldn’t break the expression if i change those values, right?
I’d be really grateful if somebody, or even the legendary Dan Ebbert himself could fix this for me. I’ve got a ton of layers using this expression, and sometimes it works, sometimes it doesn’t.
Many thanks in advance.
James.
James
Editor / After Effects / Audio Design
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4 Replies
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If your comp is long enough, Math.exp will eventually reach infinity. This variation should fix it:
k=16; // final scale
a=5; // how quickly the bounce ends
b=20; // how many bounces it'll do (that is, the bounce speed)
t = time-inPoint;
if (t < 10/a){
x=k*(1-Math.exp(-a*t)*Math.cos(b*t));
[x,x]
}else
[k,k]
Dan
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Ah, Dan! You are an absolute star! Thank you so much !
James
Editor / After Effects / Audio Design
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Is there a reverse solution to this? To make items wobble back to 0%?
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Something like this maybe:
tOut = 10; // time to finish reverse out
k=16; // final scale
a=5; // how quickly the bounce ends
b=20; // how many bounces it'll do (that is, the bounce speed)
t = time-inPoint;if (t < 10/a){
x=k*(1-Math.exp(-a*t)*Math.cos(b*t));
[x,x]
}else if (t < tOut - 10/a){
[k,k];
}else if (t < tOut){
t = tOut - t;
x=k*(1-Math.exp(-a*t)*Math.cos(b*t));
[x,x]
}else
[0,0]
Dan
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