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Inertial bounce with clamp
I’m using the classic inertial bounce expression on position and rotation properties, but want to clamp the max value to the value of the second keyframe. It would be like the layer hits a wall or rotates against a wall. I’ve found a solution or two, but nothing that seems to work universally without breaking.
Thanks,
Andrésamp = .1;
freq = 3.0;
decay = 9.0;n = 0;
if (numKeys > 0){
n = nearestKey(time).index;
if (key(n).time > time){
n--;
}}
if (n == 0){ t = 0;
}else{
t = time - key(n).time;
}
if (n > 0 && t < 1){
v = velocityAtTime(key(n).time - thisComp.frameDuration/10);
value + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
}else{value} -
3 Replies
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This might be what you’re looking for:
https://www.motionscript.com/articles/bounce-and-overshoot.html#kf-overshoot
Dan
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I’ve been trying this one from your site, but it behaves so different than my initial expression no matter how I play with my sliders for the variables. How would we keep my initial expression, but with a clamp on the second keyframe?
e = .7;
g = 5000;
nMax = 9;n = 0;
if (numKeys > 0){
n = nearestKey(time).index;
if (key(n).time > time) n--;
}
if (n > 0){
t = time - key(n).time;
v = -velocityAtTime(key(n).time - .001)*e;
vl = length(v);
if (value instanceof Array){
vu = (vl > 0) ? normalize(v) : [0,0,0];
}else{
vu = (v < 0) ? -1 : 1;
}
tCur = 0;
segDur = 2*vl/g;
tNext = segDur;
nb = 1; // number of bounces
while (tNext < t && nb <= nMax){
vl *= e;
segDur *= e;
tCur = tNext;
tNext += segDur;
nb++
}
if(nb <= nMax){
delta = t - tCur;
value + vu*delta*(vl - g*delta/2);
}else{
value
}
}else
value -
I actually found a previous post. Does this seem logical (I added an amp factor with a slider)?
// https://forums.creativecow.net/thread/227/18170freq = effect("Freq")("Slider");
decay = effect("Decay")("Slider");n = 0;
p = thisPropertyif (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)*effect("Amp")("Slider");w = freq*Math.PI*2;
amp *= Math.floor(t*freq*2)%2 ? 1 : -1; value + amp* Math.sin(t*w)/Math.exp(decay*t)/w
}else{
value
}
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