• Adobe After Effects Expressions

  alternating rotation between position keyframes

  Posted by Frank Feijen on February 4, 2010 at 9:12 pm

  Hi there,

  I have a layers position keyframed, but now i’d like to add some degree of alternating random rotation.
  for example:
  at poskeyframe1 – rotation:+12
  at poskeyframe2 – rotation:-20
  at poskeyframe3 – rotation:+22
  at poskeyframe4 – rotation:-6
  …
  I must admit not to have clue on how to do this. But since there will be tons of positionkeyframes, an expression would surely save my wrists.

  Frank Feijen replied 16 years, 3 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  February 4, 2010 at 9:41 pm

  This might be close:

  maxVal = 25;
  minVal = 5;
  n = 0;

  if (position.numKeys > 0){
  n = position.nearestKey(time).index;
  if (position.key(n).time > time) n–;
  }
  if (n == 0){
  seedRandom(1,true);
  random(minVal,maxVal);
  }else if (n == position.numKeys){
  seedRandom(n,true);
  a = random(minVal,maxVal);
  if (n%2) a else -1;
  }else{
  seedRandom(n,true);
  a1 = random(minVal,maxVal);
  seedRandom(n+1,true);
  a2 = random(minVal,maxVal);
  if (n%2) a2 = -a2 else a1 = -a1;
  t1 = position.key(n).time;
  t2 = position.key(n+1).time;
  linear(time,t1,t2,a1,a2);
  }

  Dan
• 

  Frank Feijen

  February 4, 2010 at 9:48 pm

  Just 1 word for you: AWESOME!!

  works perfect, thanks.

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