• Adobe After Effects Expressions

  Opacity semi-random issue

  Posted by Trevor Navarre on January 15, 2018 at 8:59 pm

  I have a displacement map I would like to flicker on and off randomly, however I would like it to be off more that on and only be on a few times rather than a majority.

  Here’s what I came up with :

  random(0,100);
  if (thisComp.layer(“displace”).transform.opacity < 90) 0 else 100;

  It doesnt seem to randomize once I put all of this in…. any help would be appreciated. Also if there is a way that when it does switch “on” it stays on for maybe 10 frames I’d appreciate a hint on that! Thanks in advance for any help!

  random(0,100);
if (thisComp.layer("displace").transform.opacity < 90) 0 else 100;


  Kevin Camp replied 8 years, 6 months ago 2 Members · 4 Replies
• 4 Replies

• 

  Kevin Camp

  January 15, 2018 at 9:13 pm

  you’re close… you just need to assign the random value to a variable and compare that variable to 90 to set the opacity….

  r = random( 0, 100 ) ;
  if ( r < 90 ) 0 else 100 ;

  note, if the less than sign gets replaced with < manually replace it with the symbol.

  Kevin Camp
  Art Director
  KCPQ, KZJO & KRCW
• 

  Trevor Navarre

  January 15, 2018 at 9:20 pm

  Thanks! Seems to be working!
• 

  Trevor Navarre

  January 15, 2018 at 10:49 pm

  This is kind of primative but below is what I’m trying to do but just unable to articulate. Any clue?

  r = random( 0, 100 ) ;
if ( r < 90 ) 0 else 100 ;
if (r = 100) (r = 100 for 8 frames)
• 

  Kevin Camp

  January 16, 2018 at 6:32 pm

  you could try using posterizeTime() to have a new random value generated every 8 frames (instead of every frame):

  hold = 8 ; // value in frames
  fps = 1 / thisComp.frameDuration / hold ;
  posterizeTime( fps ) ;
  r = random( 0, 100 ) ;
  if ( r < 90 ) 0 else 100 ;

  Kevin Camp
  Art Director
  KCPQ, KZJO & KRCW

Reply to this Discussion! Login or Sign Up