• Adobe After Effects Expressions

  How can I figure out the legnth of a path.

  Posted by Chris Scalzo on March 16, 2015 at 4:36 pm

  The problem I’m having is I’m animating a stroke on with trim paths (which is measured in percentage of completion), and have a text layer writing it on with the path options. The First margin property is measured by length of the path. I plugged in a slider temporarily to adjust this value to re synchronize them after moving the path around. I would much prefer to somehow read the length of the path with another expression so it stays lined up as I adjust the path.

  Charlie Leroy replied 11 years, 4 months ago 3 Members · 3 Replies
• 3 Replies

• 

  Dan Ebberts

  March 16, 2015 at 5:44 pm

  I’m not sure if this helps, but it’s the only thing I can think of. If you copy the path and paste it into the position property of a null, the null will trace out the path at a constant speed over a two second period. So if you have a slider controlling the percentage, you can convert that to pixels traveled with something like this:

  pct = effect(“Slider Control”)(“Slider”)/100;
  thisComp.layer(“Null 1”).position.speedAtTime(0)*2*pct;

  Dan
• 

  Chris Scalzo

  March 16, 2015 at 6:29 pm

  Thank you for the quick response. I spend around two hours searching for a quick solution. What I have now would probably be easier to manipulate for my current needs. I saw a response you made on paths to someone else stating there is little you can read with expressions on a path. I am running 2014.1.1 and was hoping this would have been updated in 2014.1.2 like the text bounds thing. Anyway, thanks again. I have much respect for your content on creativecow. 🙂
• 

  Charlie Leroy

  March 17, 2015 at 3:50 pm

  Hello Chris,
  If I understood correctly you have your stroke going from 0% to 100% and the text layer is following the “moving tip” of the stroke. is that correct?

  if it is, then you can do this;
  you know the First margin starts and the first margin finish

  this should make your text starts and finish at the same time as the stroke appears ( if both the path and the stroke are the same obviously)
  on the First margin value
  //initial margin value
var x=1641;
//final margin value
var y= 3086;
//the End trim percentage
var z= thisComp.layer("Shape Layer 1").content("Trim Paths 1").end;
//cross product
value =z*(y-x)/100+x

  hope it helps.

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