• Adobe After Effects Expressions

  Random motion at intervals > bounce at each interval

  Posted by Andres Torres on March 26, 2009 at 2:50 pm

  I’d like to combine Dan’s expression for Random motion at intervals with the Inertial Bounce expression found below. Instead of the bounce occurring at keyframes, I want them to occur at each new Random motion interval.

  // Dan’s Random Motion at intervals expression
  holdTime = .5; //time to hold each position (seconds)
  minVal = [0.1*thisComp.width, 0.1*thisComp.height];
  maxVal = [0.9*thisComp.width, 0.9*thisComp.height];

  seed = Math.floor(time/holdTime);
  seedRandom(seed,true);
  random(minVal,maxVal)

  // Inertial Bounce (moves settle into place after bouncing around a little)
  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){
  v = velocityAtTime(key(n).time – thisComp.frameDuration/10);
  amp = .05;
  freq = 4.0;
  decay = 2.0;
  value + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
  }else{
  value;
  }

  Dustin Wilson replied 7 years, 8 months ago 3 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  March 26, 2009 at 11:47 pm

  Something like this maybe:

  holdTime = .5; //time to hold each position (seconds)
  t = time – Math.floor(time/holdTime)*holdTime;
  minVal = [0.1*thisComp.width, 0.1*thisComp.height];
  maxVal = [0.9*thisComp.width, 0.9*thisComp.height];

  seed = Math.floor(time/holdTime);
  seedRandom(seed,true);
  p1 = random(minVal,maxVal);

  seedRandom(seed-1,true);
  p0 = random(minVal,maxVal);

  v = p1 – p0;
  amp = .05;
  freq = 4.0;
  decay = 2.0;
  p1 + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);

  Dan
• 

  Dustin Wilson

  November 16, 2018 at 5:15 pm

  Dan the man!

  Dan, I can’t thank you enough. This is exactly what I was looking to accomplish! Thank you for your time and help!

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