• Adobe After Effects Expressions

  Controlling frequency of” 0 or 100 opacity” expression

  Posted by Nicholas Roy on August 20, 2018 at 10:49 pm

  Hello folks,
  I’ve been noddling different approaches to achieving this and can’t seem to get it right.

  I have multiple layers. I’d like their opacity to randomly flicker on/off so 0/100 (nothing in between)

  Thats easy enough using:

  Math.round(random())*100

  Now I would like to ramp up the frequency of the on state by time (so at 0 seconds have everything be off, 1 second 20% is flickering on, 2 seconds 50% is on, etc.).

  I’d love to do this with a slider whereas I could set a nice curve to the ramp. Any insight would be greatly appreciated. Thank you.

  Nicholas Roy replied 8 years ago 2 Members · 6 Replies
• 6 Replies

• 

  Dan Ebberts

  August 20, 2018 at 11:46 pm

  Something like this maybe:

  s = effect(“Slider Control”)(“Slider”).value;
  random(100) < s ? 100 : 0

  Dan
• 

  Nicholas Roy

  August 21, 2018 at 3:52 pm

  Dan that works exactly as I requested. Problem is it gave me a seizure. I’m wondering if there is a way to do this same effect using the wiggle expression. So if I had a wiggle with both frequency and amount controlled by a slider with an or/else function to always deliver either 0 or 100?
• 

  Dan Ebberts

  August 21, 2018 at 3:57 pm

  Now you’re venturing into much more complex territory:

  https://www.motionscript.com/articles/speed-control.html#wiggle

  Dan
• 

  Nicholas Roy

  August 21, 2018 at 4:26 pm

  I’ve been trying really really hard to avoid reading that. It also gives me seizures. But I have the time today to try and learn so here goes.

  I’ve also got a 1/2 way decent shortcut working using this workaround:

  https://lesterbanks.com/2012/02/creating-an-on-off-expression-in-after-effects/

  Thanks Dan you the man.
• 

  Dan Ebberts

  August 21, 2018 at 5:10 pm

  You should be fine as long as you don’t try and animate the wiggle frequency.

  Dan
• 

  Nicholas Roy

  August 21, 2018 at 10:14 pm

  So the effect I was going for was to have multiple layers slowly begin to blink ON (0 or 100 opacity no in between), then I wanted the ON state to increase in frequency finally having them all hold ON after 5 seconds.

  Ok so I’m no Dan Ebberts. Legend. But this is what I came up with and it works and gives me some control. It’s a basic wiggle expression with an if/else function tied to 3 slide controllers.

  code:

  freq = thisComp.layer(“slider”).effect(“frequency”)(“Slider”)
  amp = thisComp.layer(“slider”).effect(“amount”)(“Slider”)
  control = thisComp.layer(“slider”).effect(“control”)(“Slider”)

  if (wiggle(freq, amp) + control < 1) { 0 } else 100

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