Opacity vary from 0 to 100 with 2 markers

[Dan Ebberts]

If there will be more than 3 markers in the sequence, I think you need to show how that looks after the 3rd marker, because it’s not clear (to me at least). But yes, there should be an algorithm that works, once you define all the rules.

[Jean Livenais]

Yes, it wasn’t clear… we would need a third marker named “F” for Fade, with 100 opacity, where it starts to fade until the “H” marker.

So the marker’s sequence would be:

S = 100 opacity

F = 100 opacity, and it starts to fade until the “H” marker

H = 0 opacity, until 1 frame before S

S = Goes back to 100 opacity

F

H

…

The sequence would be S F H that repeats in this order.

Here you can see the variation of the opacity would be like with more than 3 markers.

OPACITY-EXAMPLE_2.jpg 75 KB Image File - Click to view

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[Dan Ebberts]

OK, so it would be something like this:

m = thisComp.marker;
val = value;
if (m.numKeys > 0){
  n = m.nearestKey(time).index;
  if (time < m.key(n).time) n--;
  if (n > 0){
    c = m.key(n).comment;
    if (c == "S"){
      val = 100;
    }else if (c == "F"){
      if (n < m.numKeys){
        val = linear(time,m.key(n).time,m.key(n+1).time,100,0);
      }else{
        val = 0;
      }
    }else if (c == "H"){
      val = 0;
    }
  }
}
val

It could be more complicated, for example, if there could be markers that don’t have a comment of “S”, “F”, or “H”, or you have them in the wrong order, but this should give you the idea. This is set up for comp markers. If you want to use layer markers, just change the first line to:

m = marker;

[Jean Livenais]

It’s working perfectly.

Thank you Dan for taking the time to solve this idea.

It’s great to have people ready to help.

[Brie Clayton]

Thank you for solving this issue, Dan!