• Adobe After Effects Expressions

  Loop undulations to length of comp

  Posted by Trevor Morgan on July 15, 2021 at 3:47 pm

  Greetings,

  I have a comp that is 7sec long with a layer that undulates up and down. I’m having trouble figuring out how to make the undulations loop to the comp length perfectly. I’m using the undulation expression via Dan’s motionscript.com site:

  xAmp = 3; //height of undulations (pixels)
  xFreq = .3; //undulations per second
  xSpeed = 150; //speed of wave (pixels per second)
  
  wl = xSpeed/xFreq; //wavelength (pixels)
  phaseOffset = ((position[0]%wl)/wl)*2*Math.PI;
  y = xAmp*Math.sin(2*Math.PI*xFreq*time + phaseOffset);
  value + [0,y]

  Any help with this greatly appreciated!

  -Trevor

  Trevor Morgan replied 4 years, 10 months ago 2 Members · 3 Replies
• 3 Replies

• 

  Dan Ebberts

  July 15, 2021 at 10:09 pm

  I think you’d need to change xFreq to something that gives you a number of complete undulations over your 7 second comp duration. Try .286
• 

  Dan Ebberts

  July 15, 2021 at 11:35 pm

  Actually, this is a better way to do it:

  xAmp = 50; //height of undulations (pixels)
  n = 2; // number of undulations
  xFreq = n/thisComp.duration; // undulations per second
  xSpeed = 150; //speed of wave (pixels per second)
  wl = xSpeed/xFreq; //wavelength (pixels)
  phaseOffset = ((position[0]%wl)/wl)*2*Math.PI;
  y = xAmp*Math.sin(2*Math.PI*xFreq*time + phaseOffset);
  value + [0,y]
• 

  Trevor Morgan

  July 15, 2021 at 11:57 pm

  SO FRICKIN STOKED!

  totally works. Also works if I change the comp length. This is awesome!

  Thank you so much

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