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Using the loop expression to loop an expression
Hi all,
I’ve been using some great code of Dan Ebberts for keyframe overshoot
freq = 3;
decay = 5;n = 0;
if (numKeys > 0){
n = nearestKey(time).index;
if (key(n).time > time) n--;
}
if (n > 0){
t = time - key(n).time;
amp = velocityAtTime(key(n).time - .001);
w = freq*Math.PI*2;
value + amp*(Math.sin(t*w)/Math.exp(decay*t)/w);
}else
valueIt’s been working a treat, but I now want to to loop. I tried adding
loopOut(type = "cycle", numKeyframes = 0)
on the next line but it didn’t work.
What should I do to make the keyframes repeat indefinitely?
Thanks in advance.
Cheers,
Rob -
6 Replies
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Instead of doing the overshoot at the last keyframe you want it to go back to the first keyframe? That doesn’t sound right.
Dan
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Hi Dan,
I’m using it to give a repetitive pulse to an object, so it expands and contracts with the nice overshoot reduction in movement. I’d set a number of keyframes to generate the pulse, then duplicate the last keyframe a little after the pulse to set the frequency of the pulse.
Cheers,
Rob -
Try this:
t = time;
if (numKeys > 1){
if (t > key(numKeys).time){
t = key(1).time + (t - key(numKeys).time)%(key(numKeys).time - key(1).time);
}
}freq = 3;
decay = 5;n = 0;
if (numKeys > 0){
n = nearestKey(t).index;
if (key(n).time > t) n--;
}
if (n > 0){
t2 = t - key(n).time;
amp = velocityAtTime(key(n).time - .001);
w = freq*Math.PI*2;
valueAtTime(t) + amp*(Math.sin(t2*w)/Math.exp(decay*t2)/w);
}else
valueAtTime(t)
Dan
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Dan that works a treat! Thanks very much.
But holy moly, thats more complicated than I’d hoped. If you have the time, could explain how it works and (forgive me if it’s a dumb question) but why just adding the standard loop expression doesn’t work?
Cheers,
Rob -
loopOut() loops the property’s keyframed value, not anything expression-generated. So by adding it to the end of another expression, you just overwrite the result of that expression with the loopOut() result.
The first part of the new expression calculates the current loop time and plugs it into variable “t”, which is used in place of “time” in the original expression.
Dan
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That makes sense, thanks Dan!
Cheers,
Rob
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