• Adobe After Effects Expressions

  Opacity Driven Expression

  Posted by Barry Suydam on March 16, 2011 at 4:36 pm

  I have 19 numerical layers stacked(1-19) one on top of the other. I key-framed a line/bar to scroll from top (1) to Bottom (19). What I am looking for is a way to have them appear on screen as the bar passes over them(go from 0 opacity to 100) Any help would be much appreciated.

  I intend on doing the same with the 19 corresponding text layers(chapter titles)but this is a good start?

  Dan Ebberts replied 15 years, 2 months ago 2 Members · 5 Replies
• 5 Replies

• 

  Dan Ebberts

  March 16, 2011 at 6:05 pm

  I’m guessing this may not really be what you want, but this is a simple stab at it. Each layer should pop on as the center of layer “Bar” passes (vertically) its own center.

  L = thisComp.layer(“Bar”);
  p = L.toWorld(L.anchorPoint);
  p[1] > toWorld(anchorPoint)[1] ? 100 : 0;

  Dan
• 

  Barry Suydam

  March 16, 2011 at 7:08 pm

  It is an honor to be educated by Mr. Ebberts himself. It worked as it should. Thank you so much. Is there a simple way to ease in the opacity. If so that would be over the top assistance? Thanks again Dan.
• 

  Dan Ebberts

  March 16, 2011 at 7:38 pm

  This version should ease in the opacity as the bar moves from the layer’s upper edge to its center:

  L = thisComp.layer(“Bar”);
  p = L.toWorld(L.anchorPoint);
  easeIn(p[1],toWorld([0,0])[1],toWorld(anchorPoint)[1],0,100)

  Dan
• 

  Barry Suydam

  March 18, 2011 at 1:35 pm

  Great, thanks…

  I found this expression on your website////

  point1=this_layer.position;
  point2=thisComp.layer(“Text Bar”).transform.scale;

  delta=sub(point1, point2);

  distance=length(delta);
  linear(distance, 0,50, [150,150],[100,100]);

  What I am trying to accomplish is as that bar moves past the text layer it moves the layer position 50 pixels on the x axis only and once it passes completely it returns to its original value. So what I came up with is the following however it don’t work. Any help would be appreciated.

  point1=this_layer.position;
  point2=thisComp.layer(“Text Bar”).transform.position;
  x = value =50
  delta=sub(point1, point2);
  distance=length(delta);
  ease(distance, 0,50, [x,[1]],[[0],[1]]);
• 

  Dan Ebberts

  March 18, 2011 at 6:25 pm

  This probably gets you closer:

  p1=transform.position;
  p2=thisComp.layer(“Text Bar”).transform.position;
  distance=length(p1,p2);
  ease(distance,0,50,value+[50,0],value)

  Dan

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