Is this expression possible?

Adobe After Effects Expressions

Is this expression possible?

Posted by Erin Shelby on September 13, 2005 at 4:55 pm

Is it possible to write an expression where something is triggered by an objects perimeter touching something?

For example: a Square that scales upward until it hits title safe – then stops.
Or a Circle that moves in X until it hits another layer which causes it to stop.

No need to write the actual code, maybe psudeo-code or a point in the right direction. Specifically I’m trying to figure out which actual command to use if there is perimeter triggers.

Dan Ebberts replied 20 years, 8 months ago 2 Members · 1 Reply
1 Reply

Dan Ebberts

September 13, 2005 at 5:25 pm

There aren’t built-in triggers for stuff like that, but you can still do it (but it can get kind of messy). Here’s an example. This expression will scale up a square over three seconds so that it stops at title safe (10/90%).


scaleTime = 3;

if (position[0] > thisComp.width/2){
  xScale = (thisComp.width*.9 - position[0])/(width/2);
}else{
  xScale = (position[0] - thisComp.width*.1)/(width/2);
}
if (position[1] > thisComp.height/2){
  yScale = (thisComp.height*.9 - position[1])/(height/2);
}else{
  yScale = (position[1] - thisComp.height*.1)/(height/2);
}
s = Math.min(xScale,yScale);

linear(time,0,scaleTime,valueAtTime(0),[s,s]*100)

Dan

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