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From: Byron Nash <byronnash@gmail.com>
Date: Wed, 9 May 2012 10:42:43 -0400
Message-ID: <CANGV+5r58iMSNmKf6QMSmxnaxiRjAvB-Dmd=a0xS7ubEdopN5A@mail.gmail.com>
Subject: Expressions: Decay after trigger
To: After Effects Mail List <AE-List@media-motion.tv>
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I am writing an expression to bring the opacity of a layer up when it
another layer comes close to it. I'd like to have it decay at a different
rate than it builds. Here's what I have going on:

o = transform.opacity;
s = thisComp.layer("center").transform.scale[0]/100; //use the scale to
affect the radius of influence of the null
l = length(transform.position, thisComp.layer("center").transform.position);
lprev = length(transform.position.valueAtTime(time-thisComp.frameDuration),
thisComp.layer("center").transform.position.valueAtTime(time-thisComp.frameDuration));
if(lprev > l){
  l = lprev;
}
o - (l/s);


My attempt to look at the previous frame doesn't seem to be working.

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I am writing an expression to bring the opacity of a layer up when it anoth=
er layer comes close to it. I&#39;d like to have it decay at a different ra=
te than it builds. Here&#39;s what I have going on:<div><br></div><div><div=
>

<font face=3D"courier new, monospace">o =3D transform.opacity;</font></div>=
<div><font face=3D"courier new, monospace">s =3D thisComp.layer(&quot;cente=
r&quot;).transform.scale[0]/100; //use the scale to affect the radius of in=
fluence of the null</font></div>

<div><font face=3D"courier new, monospace">l =3D length(transform.position,=
 thisComp.layer(&quot;center&quot;).transform.position);</font></div><div><=
font face=3D"courier new, monospace">lprev =3D length(transform.position.va=
lueAtTime(time-thisComp.frameDuration), thisComp.layer(&quot;center&quot;).=
transform.position.valueAtTime(time-thisComp.frameDuration));</font></div>

<div><font face=3D"courier new, monospace">if(lprev &gt; l){</font></div><d=
iv><font face=3D"courier new, monospace">=A0 l =3D lprev;</font></div><div>=
<font face=3D"courier new, monospace">}</font></div><div><font face=3D"cour=
ier new, monospace">o - (l/s);</font></div>

</div><div><br></div><div><br></div><div>My attempt to look at the previous=
 frame doesn&#39;t seem to be working.=A0</div>

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