• Adobe After Effects Expressions

  Relative movement

  Posted by Pontus Danielsson on February 14, 2013 at 7:39 am

  Forgive me if I don’t use the correct terms, but I’ll try to explain my problem. I have layer “A” positioned in the middle of the composition. Layer “B” is also located in the center of the composition but offset in z-space. When I move layer A in the x-axis, I want layer B to follow, but with an extra movement. For example, if I animate layer A 100px to the right, I want layer B to move 150px to the right from the center. And if I move layer A 100px to the left of the center I want layer B to move 150px to the left.

  So if layer A was animated from -100 px from composition center to 100px from center, layer B would move a total of 300 px and layer A 200 px.

  Any idea what expression to use?

  Thanks!

  /Pontus

  Pontus Danielsson replied 13 years, 5 months ago 2 Members · 4 Replies
• 4 Replies

• 

  Kevin Camp

  February 14, 2013 at 9:14 pm

  i think this does what you want:

  target = thisComp.layer(“A”);
  x = 1.5*(target.position[0]-thisComp.width/2)+thisComp.width/2;
  [x,value[1],value[2]]

  Kevin Camp
  Senior Designer
  KCPQ, KMYQ & KRCW
• 

  Kevin Camp

  February 14, 2013 at 9:23 pm

  actually, that only works if the layer A is moving relative to the center of the comp…. let me think about this for a bit more…

  Kevin Camp
  Senior Designer
  KCPQ, KMYQ & KRCW
• 

  Kevin Camp

  February 14, 2013 at 9:55 pm

  if you can use a null (or other layer) as a parent to both layers A and B, and you make layer A’s average position relative to the parent (so it’s x position ranges from say -100 to 100, or -200 to 200), then this simple expression would work:

  target = thisComp.layer(“A”);
  x = 1.5 * target.position[0];
  [x,value[1],value[2]]

  essentially, you’re using the parent to zero the position of both layers to make the math easy.

  Kevin Camp
  Senior Designer
  KCPQ, KMYQ & KRCW
• 

  Pontus Danielsson

  February 15, 2013 at 8:00 am

  Works like a charm!
  Many thanks!

  /Pontus

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