• Adobe After Effects Expressions

  Fade In and Out

  Posted by Deepak Kumar on January 3, 2019 at 5:41 pm

  Can anyone Plz describe me How This Expression Work? When i Appy this Into Opacity it Makes Laye fade in and Fade Out I want To know physics behind it.

  i = linear(time, inPoint, inPoint+.5, 0, 100);
o = linear(time, outPoint-.5, outPoint, 0, 100);
i-o

  Dan Ebberts replied 7 years, 7 months ago 3 Members · 4 Replies
• 4 Replies

• 

  Kalleheikki Kannisto

  January 3, 2019 at 6:02 pm

  Variable “i” gets its value from remapping the time value between the inpoint time of the layer and the inpoint time plus 0.5 seconds to the range of 0 to 100. Thus at inpoint the value of i is 0, from where it rises up to 100 in the following 0.5 seconds.

  Variable “o” gets it’s value similarly (in reverse) at the endpoint of the layer by remapping time from 0 to 100.

  When you subtract o from i you get both variables affecting the opacity.

  To understand the linear() function better, check it out in the AE expressions reference.

  Kalleheikki Kannisto
  Senior Graphic Designer
• 

  Deepak Kumar

  January 8, 2019 at 9:02 am

  Why Only subtract Works Perfect Why It Doesn’t when i do “i + o”
• 

  Kalleheikki Kannisto

  January 8, 2019 at 12:38 pm

  If you add the values then in the end it goes from 100 to 200, not 100 to 0.

  Kalleheikki Kannisto
  Senior Graphic Designer
• 

  Dan Ebberts

  January 8, 2019 at 2:17 pm

  Here are a couple of other ways to do it that might make more sense (because the calculation for o goes in the direction you expect):

  i = linear(time, inPoint, inPoint+.5, 0, 100);
  o = linear(time, outPoint-.5, outPoint, 100, 0);
  Math.min(i,o)

  i = linear(time, inPoint, inPoint+.5, 0, 100);
  o = linear(time, outPoint-.5, outPoint, 100, 0);
  time < (inPoint+outPoint)/2 ? i : o

  Dan

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