• Adobe After Effects Expressions

  Motion Trails with Random Position Seed

  Posted by Madli Man on August 3, 2013 at 8:26 pm

  Hi forum,

  Im got expression from Motionscript for motion trails. Everything is working good. But i wanted to add some 3D random position to the follower position by changing slider as a 3D random seed.

  How can i do that?

  Thank you.
  Madli

  delay = 5
d = delay*thisComp.frameDuration*(index - 1);
thisComp.layer(1).position.valueAtTime(time - d)


  Madli Man replied 12 years, 9 months ago 3 Members · 5 Replies
• 5 Replies

• 

  Darby Edelen

  August 3, 2013 at 10:52 pm

  If you only want to randomly offset the followers in Z you could add something like this to the expression:

  seedRandom(index, true);
min = -5;
max = 5;
z = random(min, max);
...current expression... + [0,0,z];

  The expression as you currently have it would go where it says “…current expression…”

  The above would offset each follower by a random amount between -5 and 5 on the Z axis. This offset will be constant per layer.

  Darby Edelen
• 

  Madli Man

  August 4, 2013 at 1:44 am

  Thank you Darby for quick reply.

  it work perfect. I add-on some expression in it.

  Thank you.

  rand=thisComp.layer("Control").effect("Position Random Seed")("Slider");
delay = thisComp.layer("Control").effect("Delay")("Slider")
min = thisComp.layer("Control").effect("Min Position")("Slider");
max = thisComp.layer("Control").effect("Max Position")("Slider");
seedRandom(rand, true);
x = random(min, max);
y = random(min, max);
z = random(min, max);
d = delay*thisComp.frameDuration*(index - 1);
thisComp.layer(1).position.valueAtTime(time - d)+[x,y,z];
• 

  Madli Man

  August 9, 2013 at 6:59 pm

  Hi forum,

  Just one more quick question. How can i adjust this random value either min or max value.
  eg:
  min =-180;
  max = 180;
  random either one of these 2 value not between them.

  Thanks forum.

  seedRandom(index, true);
min = -5;
max = 5;
z = random(min, max);
...current expression... + [0,0,z];
• 

  Dan Ebberts

  August 9, 2013 at 7:28 pm

  This should work:

  seedRandom(index, true);
  min = -5;
  max = 5;
  z = random() < .5 ? min : max;
  …current expression… + [0,0,z];

  Dan
• 

  Madli Man

  August 10, 2013 at 3:36 pm

  Thank you Mr.Dan.

  its worked. Much appreciated. 🙂

  Madli

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