• Adobe After Effects Expressions

  Continuous bounce

  Posted by Kostas Bartsokas on May 15, 2014 at 7:14 pm

  Hi to all.

  I am quite new to expressions. I am creating an animation with a sign hovering over a persons head. I want the sign to bounce continuously (with Inertia) and perhaps rotate a bit to either side. I have found the Inertia Bounce expression but I couldn’t get it to work, cause it always stops after a few bounces.

  Could anyone help?

  Thanks in advance.

  K.

  Kostas Bartsokas replied 12 years, 4 months ago 2 Members · 3 Replies
• 3 Replies

• 

  Kevin Camp

  May 15, 2014 at 8:33 pm

  for position you could use something like this:
  freq = 1; //bounces per second
amp = 100; //bounce height in pixels

  y = Math.sin(time*Math.PI*freq)*amp/2;
value + [0,y]

  it will cause a layer to continually bounce in an elastic fashion.

  if you needed a hard bounce (like a ball bouncing off the ground), you could change the third line to this:
  y = Math.abs(Math.sin(time*Math.PI*freq))*amp;

  for rotation, since you could use the same expression but change the last line to this
  value + y

  Kevin Camp
  Art Director
  KCPQ, KZJO & KRCW
• 

  Kevin Camp

  May 15, 2014 at 8:34 pm

  also, if you want more info on expression like these, you can find more on them at motionscript.com.

  these were based on the expression found here:
  https://www.motionscript.com/mastering-expressions/simulation-basics-3.html

  Kevin Camp
  Art Director
  KCPQ, KZJO & KRCW
• 

  Kostas Bartsokas

  May 16, 2014 at 6:19 am

  Hi Kevin

  it worked like a charm!! Thank you very much! I’ll have a look at Motionscript.

  Thanks!
• 

  Viktor Vaughn

  January 5, 2021 at 3:27 pm

  Hi Kevin,

  Is there any way to randomise the freq or amp to parimeters i can set?

  Much appreciated

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