• Adobe After Effects Expressions

  Modify Expand Contract expression

  Posted by Zach Meissner on December 18, 2008 at 11:11 pm

  maxDev = 10; // max deviation in pixels
  spd = 20; //speed of oscillation
  decay = 1.0; //how fast it slows down
  
  if (marker.numKeys > 0){
  t = time - marker.key(1).time;
  if (t >=0 ){
  x = scale[0] + maxDev*Math.sin(spd*t)/Math.exp(decay*t);
  y = scale[0]*scale[1]/x;
  [x,y]
  }else{
  value
  }
  }else{
  value
  } 

  Trying to modify the wonderful expand and contract expression that Dan made to only do it on the Y axis instead of both. I’m sure it’s simple, but i just cant figure it out. Thanks!

  Zach Meissner replied 16 years, 4 months ago 2 Members · 8 Replies
• 8 Replies

• 

  Dan Ebberts

  December 19, 2008 at 1:05 am

  This should do it:

  maxDev = 10; // max deviation in pixels
  spd = 20; //speed of oscillation
  decay = 1.0; //how fast it slows down

  if (marker.numKeys > 0){
  t = time – marker.key(1).time;
  if (t >=0 ){
  y = scale[0] + maxDev*Math.sin(spd*t)/Math.exp(decay*t);
  [value[0],y]
  }else{
  value
  }
  }else{
  value
  }

  Dan
• 

  Zach Meissner

  December 19, 2008 at 6:43 am

  Thanks Dan! Is there an easy way to disable the expression with a another layer marker, or with a checkbox control? I want to change just the Y value of text to make appear to sink into the ground at a certain time, but i cant keyframe the scale because the expression is in use. I figure it’s easy to do with a layer marker but i wasn’t sure how. Thanks a bunch!!
• 

  Dan Ebberts

  December 19, 2008 at 3:28 pm

  Ah, I think that’s because there’s an error in the expression. Try changing the long line to this:

  y = scale[1] + maxDev*Math.sin(spd*t)/Math.exp(decay*t);

  That should keep everything live for keyframing.

  Dan
• 

  Zach Meissner

  December 21, 2008 at 2:33 am

  Yes!! Thanks so much Dan!!
• 

  Zach Meissner

  December 22, 2008 at 8:33 pm

  Hey Dan, if i wanted to turn the expression on again at another layer marker, how would i modify it? I’m thinking something with the ‘key(1)’ text, but i’m not sure. Thanks!
• 

  Dan Ebberts

  December 22, 2008 at 8:44 pm

  This should trigger at each layer marker:

  maxDev = 10; // max deviation in pixels
  spd = 20; //speed of oscillation
  decay = 1.0; //how fast it slows down

  n = 0;
  if (marker.numKeys > 0){
  n = marker.nearestKey(time).index;
  if (marker.key(n).time > time){
  n–;
  }
  }

  if (n > 0){
  t = time – marker.key(n).time;
  y = scale[1] + maxDev*Math.sin(spd*t)/Math.exp(decay*t);
  [value[0],y]
  }else{
  value
  }

  Dan
• 

  Zach Meissner

  December 23, 2008 at 9:03 pm

  Thanks so much Dan!!!
• 

  Zach Meissner

  April 14, 2010 at 7:05 pm

  Hi Dan, back again. Trying to get this to only be on the X axis. I’ve replaced the X and Y text, but that didn’t work.

  How can I get the expression to only do the x and not the y?

  maxDev = 10; // max deviation in pixels
spd = 20; //speed of oscillation
decay = 1.0; //how fast it slows down

  n = 0;
  if (marker.numKeys > 0){
  n = marker.nearestKey(time).index;
  if (marker.key(n).time > time){
  n--;
  }
  }

  if (n > 0){
t = time - marker.key(n).time;
y = scale[1] + maxDev*Math.sin(spd*t)/Math.exp(decay*t);
[value[0],y]
}else{
value
}


  http://www.lab316.com

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