• Adobe After Effects Expressions

  Rotation driving limited pingpong rotation

  Posted by Patrick Vaughan on January 28, 2008 at 5:02 pm

  What I’m having trouble doing is this…

  front wheel of bike “layer A’ rotates continuously
  for every 360 degrees I need rider’s body “layer B” to rotate from -15 deg to -5 deg and then back to -15 deg. I know how to link the two properties but not how to limit and “pingpong” the “layer b”. Any and all help is greatly appreciated.

  Patrick Vaughan replied 18 years, 3 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Filip Vandueren

  January 28, 2008 at 6:21 pm

  Perhaps use a sine or cosine ? That will make a 0-360 value fluctuate between -1 and +1
  It’s smooth by nature, but it might be just the ticket:

  
r=thisComp.layer("layer A").transform.rotation
pingpong=Math.cos(degreesToRadians(r));
linear(pingpong, -1, 1, -15, -5);

• 

  Patrick Vaughan

  January 28, 2008 at 7:00 pm

  knew a sine or cosine would do it just didn’t have the language down. This works perfectly thanks a ton.

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