• Adobe After Effects Expressions

  adding randomness to an expression

  Posted by Collin Smith on September 30, 2013 at 7:18 am

  I’m trying to see if I can add a random expression to a basic radial wipe.

  The current expression on my 3D shape layer is effect(“Radial Wipe”)(1) (this was created by After Effects using the Effects preset Radial Wipe Transition).

  I have 2 keyframes set to go from 0 – 100. Pick whipped to that parameter is a slier control on another layer displaying numeric values that match the percentage of the transition (As the radial wipe progresses in the Transition Completion parameter the numeric values on my text layer match ranging from 0 – 100).

  My question:
  I’m trying to see if there is a way to have the value of the radial wipe transition randomly fluctuate (and preferably control the completion so it doesn’t go all the way back to 0% but rather stay in the upper % range).
  Does anybody have any advise or solutions for this?

  Darby Edelen replied 12 years, 11 months ago 2 Members · 3 Replies
• 3 Replies

• 

  Darby Edelen

  October 1, 2013 at 11:34 pm

  [Collin Smith] “My question:
  I’m trying to see if there is a way to have the value of the radial wipe transition randomly fluctuate (and preferably control the completion so it doesn’t go all the way back to 0% but rather stay in the upper % range).
  Does anybody have any advise or solutions for this?”

  The simplest solution might be to use the temporalWiggle(); function on the slider that is controlling the transition.

  What this does is wiggle the sampling of the keyframed value by some amount of time. I created a sample video a long time ago to show how this can be useful, the circle has only 2 position keyframes with linear interpolation and an expression applied like:

  temporalWiggle(1, framesToTime(5));

  In the above case the temporal sampling will vary by up to 5 frames (+ or -) every one second.

  Temporal Wiggle

  Darby Edelen
• 

  Collin Smith

  October 2, 2013 at 2:29 pm

  Thank You so much Darby.

  By the looks of your example video it could work.
  Now I just am at a loss on where exactly to place that expression. You mentioned a slider.

  As of right now the key frames controlling the transition are set within the Radial Wipe Effect (which is the parent to the other layer with the numeric value I pick whipped). And it’s using this Expression effect(“Radial Wipe”)(1) I attached a screen grab.

  Do I add the expression you wrote to this expression or how would I implement it?

  

  random progression to radial wipe

  Thanks in advance
• 

  Darby Edelen

  October 8, 2013 at 4:38 am

  [Collin Smith] “effect(“Radial Wipe”)(1)”

  That expression is not really doing anything. It’s telling the property to simply access its keyframed values (which the property does anyway).

  Replace that with something like:

  temporalWiggle(1, framesToTime(5));

  Increase the first parameter to increase the frequency of the wiggle and the second to increase the amount.

  Darby Edelen

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