• Adobe After Effects Expressions

  Random position a square in a range of values for a specific amount of time

  Posted by Hassan Ganari on August 17, 2019 at 4:49 pm

  Hi guys,

  I have 1000x1000px comp with 10sec duration, and a 200x200px square layer.
  I want the square to show up in EVERY 2 seconds (fade in then out) but every time in a different position, i need that position to be picked random from a range of values.

  range = ([0,0],[0,200],[200,0],[0,400],[400,0],[0,600])

  I am scratching my head for hours in vain.
  the closest i got was in this link https://forums.adobe.com/thread/2317002

  This needs to be an expression, not a script please.

  Thank you very very much.

  Dan Ebberts replied 6 years, 11 months ago 2 Members · 3 Replies
• 3 Replies

• 

  Dan Ebberts

  August 17, 2019 at 7:22 pm

  try these:

  
// opacity

  fadeTime = .5;
  period = 2;
  t = time%period;
  if (t < period/2)
  ease(t,0,fadeTime,0,value)
  else
  ease(t,period-fadeTime,period,value,0)

  //position

  period = 2;
seed = Math.floor(time/period);
positions = [[0,0],[0,200],[200,0],[0,400],[400,0],[0,600]];
seedRandom(seed,true);
i = Math.floor(random(positions.length));
positions[i];


  Dan
• 

  Hassan Ganari

  August 17, 2019 at 9:23 pm

  Thank you so much Dan,

  that worked !

  Now I got that problem when I hit play, the same pattern of position is repeated, so i tried to put a slider control and inject it in the seedRandom but i clearly miss the syntax and the algorythm !

  Thank you again for your help, it’s sooooOO cool ^^
• 

  Dan Ebberts

  August 17, 2019 at 11:13 pm

  I’m not sure I understand what issue is. You shouldn’t get a repeating pattern.

  Dan

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