• Adobe After Effects Expressions

  Changing speed of time based value

  Posted by John Toi on August 15, 2010 at 6:19 pm

  Hi again!

  I have this expression

  life = 5;
  offset = 0;
  SeedRandom(index,true); 
  pause = random(life+offset);
  if(time < pause)
  age = 0;
  else
  age = (time-pause) % life;

  The variable \\\”age\\\” pauses at 0, increases, resets back to 0 when it reaches the life value and repeats the same thing again.

  As you can see, this is a time based expression and although the value keeps increasing, the speed is constant after the pause. I want to control the speed within the expression so it will gradually slows down as the value increases and the speed will reset and repeat as the value loops back.

  However, I cannot get the speed to gradually stop. Subtracting time does not work as the speed stays constant and only slow it down altogether. The linear method only allows me to change the speed but not gradually.

  Is there a way to gradually change it and if so, how?

  Thanks in advance!

  John Toi replied 16 years ago 2 Members · 3 Replies
• 3 Replies

• 

  Dan Ebberts

  August 15, 2010 at 7:34 pm

  It’s hard to tell what you’re trying to do exactly, but maybe this will help:

  
life = 5;
offset = 0;
seedRandom(index,true);
pause = random(life+offset);
if(time < pause)
age = 0;
else
age = easeOut((time-pause) % life,0,life,0,life);


  Dan
• 

  John Toi

  August 17, 2010 at 8:14 am

  Thanks for the reply.
  From what I understand, the easeOut() function interpolates the values like the linear function and adds an ease to each end. However, i was trying to get the speed to constantly decrease as the value increases from 0 to the value of the life variable and then to repeat the same thing as the value resets to 0.

  Thanks again
• 

  John Toi

  August 26, 2010 at 7:57 pm

  Nevermind, solved it.
  life = 5; // life
  offset = 0; // pause offset
  res = 5; // resistance

  seedRandom(index,true);
  pause = random(life+offset);
  if(time < pause)
  age = 0;
  else
  age = (time-pause) % life;
  x = age*age;
  linear(x,0,(life*life),0,res);

  Based on the fact that squaring time increases the speed.

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