• Adobe After Effects

  Random blink for opacity

  Posted by Danielle Masek on November 18, 2011 at 7:52 pm

  I know this is a common topic, but I never found an answer to this specifically: apply a random blinking effect (to text in this case) where there is no sort of fade in/fade out of visibility–just on/off. I’ve done this manually by setting opacity keys as one frame opacity 0, next frame opacity 100, next frame opacity 0. and doing this spread out randomly. It’s a pain.
  Is this what the wiggler is for? It seems like it applies keyframes very evenly spaced when applied, which is not what I want. I want it random. I guess I’m not sure how it’s being random when the spacing is completely even. It also looks like its easing in/out–am I wrong here?

  And an off question…I’m sometimes not sure where to post my question, as it seems this could go in the AE basic forum, as well as the Techniques forum (b/c I’m asking about a technique–I think).

  **I look down at where you’re standing
  Flock of sheep all on display
  With all your lies piled up around you
  I can take it all away**

  Roland R. kahlenberg replied 14 years, 5 months ago 3 Members · 7 Replies
• 7 Replies

• 

  Walter Soyka

  November 18, 2011 at 8:16 pm

  Here’s a quick expression to do exactly this. Alt-click the Opacity property for the layer you want to apply this to, and copy and paste the following code:
  r = random();
if (r < 0.5) 0 else 100;
  Expressions are evaluated every frame. For each frame, r will be assigned a random number between 0 and 1. If r is less than 0.5 (half-way between 0 and 1), the expression will return 0 to the Opacity property (totally transparent). If not, the expression will return 100 (totally opaque).

  If you want to favor transparency or opacity, just change the 0.5 constant.

  Walter Soyka
  Principal & Designer at Keen Live
  Motion Graphics, Widescreen Events, Presentation Design, and Consulting
  RenderBreak Blog – What I’m thinking when my workstation’s thinking
  Creative Cow Forum Host: Live & Stage Events
• 

  Danielle Masek

  November 18, 2011 at 11:52 pm

  Thank you.
  Question…I want the layer to, for the first 8 seconds, be transparent, then at like 8 sec, 1 frame, to start the blinking, then 2 seconds later, be transparent again, how would I need to modify the expression? (I know I can just move the layer over but assuming I could not for some reason).

  **I look down at where you’re standing
  Flock of sheep all on display
  With all your lies piled up around you
  I can take it all away**
• 

  Roland R. kahlenberg

  November 19, 2011 at 3:58 am

  This should work –

  //Start Script
  if ((time <=8) || (time >10)){
  0
  } else {
  r=random(1);
  if (r<.5)
  0
  else
  100
  }
  // End Script

  FWIW, the “||” is the Javascript OR operator.

  HTH
  RoRK

  Intensive AE & Mocha Training in Singapore and Malaysia
  Adobe ACE/ACI (version 7) & Imagineer Systems Inc Approved Mocha Trainer
• 

  Danielle Masek

  November 21, 2011 at 9:24 pm

  I pasted that script in, changing the 8 and 10 (assuming that was referring to time) to 8:21 and 10:19 b/c those are actually the exact times. I got this error:
  after effects warning: expected: )
  Expression disabled

  **I look down at where you’re standing
  Flock of sheep all on display
  With all your lies piled up around you
  I can take it all away**
• 

  Walter Soyka

  November 21, 2011 at 9:35 pm

  [Danielle Masek] “I pasted that script in, changing the 8 and 10 (assuming that was referring to time) to 8:21 and 10:19 b/c those are actually the exact times. I got this error:
  after effects warning: expected: )
  Expression disabled”

  After Effects expressions think in decimal time, not seconds and frames, and the colons are not syntactically correct.

  Assuming you’re dealing with 29.97 fps, 8:21 is 8.7 (or 8 + 21/30), and 10:19 is 10.6333 (or 10 + 19/30). If you’re working in 23.976, it’s 8.875 and 10.791666, respectively.

  Walter Soyka
  Principal & Designer at Keen Live
  Motion Graphics, Widescreen Events, Presentation Design, and Consulting
  RenderBreak Blog – What I’m thinking when my workstation’s thinking
  Creative Cow Forum Host: Live & Stage Events
• 

  Danielle Masek

  November 21, 2011 at 9:49 pm

  I’m working in 24 fps. So would that be 8 + 21/24?

  **I look down at where you’re standing
  Flock of sheep all on display
  With all your lies piled up around you
  I can take it all away**
• 

  Roland R. kahlenberg

  November 22, 2011 at 3:13 am

  YUP!
  // Start
  if ((time <=(8+21/24)) || (time >10)) {
  0
  } else {
  r=random(1);
  if (r<.5)
  0
  else
  100
  }
  //EOS

  HTH
  RoRK

  Intensive AE & Mocha Training in Singapore and Malaysia
  Adobe ACE/ACI (version 7) & Imagineer Systems Inc Approved Mocha Trainer

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