• Adobe After Effects Expressions

  Start wiggle at timepoint X without jumping

  Posted by Jay Schweg on November 15, 2016 at 10:41 am

  Hi there

  I want to start a wiggle animation at a specific timepoint for a layer’s position.

  I am currently using this code

  
maxFreq = 3;
freq = 0;

  if (time < 2.8) {
  freq = 0; // 0 wiggles per second
  } else {
  if (freq < maxFreq) {
  freq = freq + 0.05; // wiggles per second
  }
  }

  amp = 25; // px units applied for wiggle
  loopTime = 10;
  t = time % loopTime; // % returns remainder - resets every looptime to 0
  wiggle1 = wiggle(freq, amp, 1, 0.5, t);
  wiggle2 = wiggle(freq, amp, 1, 0.5, t - loopTime);
  w = linear(t, 0, loopTime, wiggle1, wiggle2);
  [w[0], w[1]]

  This code will start my wiggeling after 2.8s. But unfortunately I can see the position jumping in the beginning. I thought I could improve it by slowly increasing the freq variable, but obviously it would not work. Any idea how I could get this to work?

  Thanks

  Jay Schweg replied 9 years, 10 months ago 2 Members · 4 Replies
• 4 Replies

• 

  Dan Ebberts

  November 15, 2016 at 5:06 pm

  Did you try ramping the amp variable from 0 to 25 instead?

  Dan
• 

  Jay Schweg

  November 15, 2016 at 5:14 pm

  I did actually. That was the first thing I did after the post. I got kind of a working example, but as I was not sure about if my code actually works (no debugging or logging option, except from a text layer output, which I didn’t want to to ;)) I stopped playing around.
  So you would say this works, by increasing the amp value?

  I also experienced problems with the following: I assume that the expression code is called everyframe. So how I can I increment a variable during my animation?
  So
  freq = freq + 0.05; Does not work at all.
  I thought maybe by not declaring it at the beginning, but this would make my expression fail.

  Is my assumption correct?

  My only other idea was to link the freq – or the amp – to time.
  So I would set something like this:
  amp = time * 0.05

  So after the first frame I would have time = 1 and amp = 0.05, right?
  And after the second time = 2, amp = 0.1.
  I hope I understand the time variable correctly…

  Any hints related to these things are welcome :).
  Thanks in advance.

  Cheers
• 

  Dan Ebberts

  November 15, 2016 at 5:30 pm

  You are correct that variables do not survive from frame to frame. You could do something like this to ramp amp from 0 to 25 over half a second:

  tStart = 2.8;
  amp = linear(time, tStart, tStart+.5, 0, 25);

  Dan
• 

  Jay Schweg

  November 15, 2016 at 5:32 pm

  Oh that’s a nice idea. I think I need to internalize some of those AE expression concepts a little bit.
  Thanks mate, for the hint. I’ll try it out.

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