• Adobe After Effects Expressions

  Opacity jumps to a higher starting point than defined in the linear() expression

  Posted by Hauke Sterner on March 6, 2023 at 4:20 pm

  Hello all!

  I’m fairly new to expressions and I have a problem with the following:
  L is a static circle that just fades in.
  M is the same circle, but it moves across the composition (only x-position).
  L is supposed to fade in once M hits the x-position of L.

  This is my expression:

  L = thisComp.layer(“Punkt”);
  M = thisComp.layer(“Punkt_Maske”);

  if (M.transform.position[0] >= L.transform.position[0]) {
  L.transform.opacity = linear(time, 0, 33);
  } else {
  0;
  }

  This expression kind of works, but the opacity of L does not start at 0 like stated in linear(), but jumps to a higher percentage and continues to 33%.

  Can somebody tell me what I’m doing wrong?

  Thanks! 🙂

  Hauke Sterner replied 3 years, 6 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  March 6, 2023 at 4:54 pm

  Your expression needs to calculate how long ago the trigger event happened. Also, you didn’t mention how long the fade in should take, so I just set it to .5 seconds:

  L = thisComp.layer("Punkt");
  M = thisComp.layer("Punkt_Maske");
  fadeDur = .5;
  if (M.transform.position[0] >= L.transform.position[0]) {
    t = time - thisComp.frameDuration;
    while (M.transform.position.valueAtTime(t)[0] >= L.transform.position[0]){
      t -= thisComp.frameDuration;
    }
    linear(time-t,0,fadeDur,0,33);
  } else {
    0;
  }
• 

  Hauke Sterner

  March 7, 2023 at 6:59 am

  Hi Dan,

  thank you very much! It works like a charm! 🙂

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