• Adobe After Effects Expressions

  Inertial Bounce Scale – NOT starting from zero

  Posted by Ed Stables on May 31, 2016 at 4:12 pm

  Hi
  I’ve been using this expression to add a bounce to scale:

  rate = 500;
  rampDur = value[0]/rate;
  freq = 3;
  decay = 5;
  w = freq*Math.PI*2;

  if (time < (inPoint+outPoint)/2){
  if (time < (inPoint + rampDur)){
  s = linear(time,inPoint,inPoint+rampDur,0,value[0]);
  }else{
  t = time – (inPoint+rampDur);
  s = value[0] + rate*Math.sin(t*w)/Math.exp(t*decay)/w;
  }
  }else{
  if (time > (outPoint – rampDur)){
  s = linear(time,outPoint-rampDur,outPoint,value[0],0);
  }else{
  t = (outPoint – rampDur) – time;
  s = value[0] + rate*Math.sin(t*w)/Math.exp(t*decay)/w;
  }
  }
  [s,s]

  What I don’t like about it is that it kicks in at the first frame of the layer, and always starts from zero. Is there a way to scale up from, say, 100% to 150% AND add a bounce to it? Preferably this wouldn’t need to occur at the start of a layer.
  Thank you
  Ed

  Dan Ebberts replied 10 years, 2 months ago 2 Members · 3 Replies
• 3 Replies

• 

  Dan Ebberts

  May 31, 2016 at 5:04 pm

  Like this maybe:

  
tStart = 1;
startVal = [100,100];
endVal = [150,150];
dur = .2;
freq = 3;
decay = 5;
w = freq*Math.PI*2;
t = time - tStart;
if (t < dur){
linear(t,0,dur,startVal,endVal);
}else{
amp = (endVal - startVal)/dur;
w = freq*Math.PI*2;
endVal + amp*(Math.sin((t-dur)*w)/Math.exp(decay*(t-dur))/w);
}


  Dan
• 

  Ed Stables

  May 31, 2016 at 6:57 pm

  Dan, thank you!
  It took me a while to work out what you did, but thanks so much. That’s a really useful expression, and I know it’s really going to come in handy. I just bought you a coffee via your tip jar.
  Hugely appreciated
  Ed
• 

  Dan Ebberts

  May 31, 2016 at 7:29 pm

  Glad you found it useful! Thanks for the tip–I appreciate it.

  Dan

Reply to this Discussion! Login or Sign Up