• Adobe After Effects Expressions

  Random duration expression

  Posted by Dimitri Sourzac on May 30, 2016 at 2:20 pm

  Hi there!
  I’m trying to make an expression on time remapping that allows me to randomly change the position of the playhead of a video. This code works but I’d like to be able to randomize the duration of each segment (segDur in the code).
  I tried to use random() but a new value is calculated every frame.
  Any ideas?

  //segDur - This variable controls how often the playhead will be changed.
segDur = 0.3;// duration of each "segment" of random time
minVal = inPoint;
maxVal = outPoint - segDur;
seed = Math.floor(time/segDur);
segStart = seed*segDur;
seedRandom(seed,true);
startVal = random(minVal,maxVal);
endVal = startVal + segDur;
linear(time,segStart,segStart + segDur, startVal, endVal);

  Dimitri Sourzac replied 10 years, 3 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  May 30, 2016 at 6:45 pm

  This should work as long as the keyframe marking the end of the video content is still there:

  
minDur = .25;
maxDur = .35;
tStart = tEnd = dur = 0;
seedRandom(index,true);
while (tEnd <= time){
tStart = tEnd;
dur = random(minDur,maxDur);
tEnd += dur;
}
seedRandom(tStart,true);
vStart = random(inPoint,key(numKeys).time-dur);
vEnd = vStart+dur;
linear(time,tStart,tEnd,vStart,vEnd)


  Dan
• 

  Dimitri Sourzac

  May 30, 2016 at 7:00 pm

  It works great!
  Thanks for your help!

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