• Adobe After Effects Expressions

  Using Expressions to Parent Scale to Audio

  Posted by Eli Echevarria on April 17, 2009 at 8:33 pm

  Hi folks,

  I’m fairly new to using expressions, so forgive me if my subject has been beaten to death in the past, but here goes.

  I am trying to animate a solid to pulse to a piece of music. Here is what I have done in a nutshell.

  1. Have two layers: a solid layer and also the audio track
  2. Selected my audio layer, and then created the “Audio Amplitude” layer using the keyframe assistant / convert audio to keyframes.
  3. On my solid, Option Clicked on scale to open up my expressions, and using the pick whip, selected the Both Channels slider from the Audio Amplitude layer, creating the following expression:

  temp = thisComp.layer(“Audio Amplitude”).effect(“Both Channels”)(“Slider”);
  [temp, temp]

  So, it works in that my solid is now thumping along with the music. I have two problems however. First, my solid is tiny. I can see that in my scale, it’s size varies from 2% – 14%, depending on the volume of the track. How do I increase the relative size of this so that instead it thumps from 98% to 100% (or something like that….I want subtle thumping). Second, how do I control the frequency of the pulse? Right now it’s pulsing like mad, where as in a perfect world it would only thump on downbeats. Any help would be appreciated!

  Eli Echevarria
  el*********@***oo.com

  Eli Echevarria replied 17 years, 1 month ago 1 Member · 0 Replies
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