Help in animating value between keyframes using expression

[Steven Kent27869994kodo]

I am working on lipsync animation using a slider. It was tedious, but I thought of a way to ease the process but I have no idea how.

I want an expression that adds a transition between two same keyframes. The slider I use has 0-100 value btw. I want an expression that works like below

• if a keyframe and the next one has a same value, the value will decrease by 0.5 between them
• but if the value of the two keyframes is greater than 50, it will increase by 0.5 instead.

I'm a complete beginner when it comes to expressions. I hope someone will help. Thank you very much in advance.

[Mylenium]

Refer to this post as an example for some of the necessary code:

https://community.adobe.com/t5/after-effects-discussions/modifying-value-at-a-specific-keyframe-with...

The methodology is pretty much the same, you just need to modify the conditionals. Also check this:

http://www.motionscript.com/design-guide/audio-trigger.html

Mylenium

[Steven Kent27869994kodo]

I somehow get how the solution there works. But with my limited understanding, I assume that those only work with 2 keyframes. What I'd like to do is make an expression to work on all keyframes and only with the same value.

I think I know how to do the right "if statement" when it comes to value. But I don't have an idea how to do one where I select only the keyframes I want among all the keyframes.

Also thanks for the audio trigger link, it looks helpful.

[Dan Ebberts]

If you apply an expression, it has to supply a value for each frame, not just at the keyframes. So it's important to specify what it needs to do in every situation. Maybe a marked-up screen shot of what you're trying to do would help.

[Steven Kent27869994kodo]

In this image, the two keyframes have the same value of 0.77 and my I idea is decrease the value by 0.5 and make it 0.22 on the part between them. Basically, just like adding another keyframe in between. I am looking for expressions that can do this on the rest of keyframes with the same value.

Sorry, I hope I explained it well.

[Dan Ebberts]

I think this is what you're describing, but I'm guessing it's not what you want:

val = value;
if (numKeys > 1){
  if (time >= key(1).time && time < key(numKeys).time){
    n = nearestKey(time).index;
    if (time < key(n).time) n--;
    if (n > 0){
      if (key(n).value == key(n+1).value){
        val = key(n).value - .5;
      }
    }
  }
}
val

[Steven Kent27869994kodo]

Tried this, but the decrease in value was applied from first keyframe instead in between of the two.

[Dan Ebberts · Accepted solution]

More like this maybe:

val = value;
if (numKeys > 1){
  if (time >= key(1).time && time < key(numKeys).time){
    n = nearestKey(time).index;
    if (time < key(n).time) n--;
    if (n > 0){
      if (key(n).value == key(n+1).value){
        mid = (key(n).time + key(n+1).time)/2;
        v1 = key(n).value;
        v2 = v1 - .5;
        if (time < mid)
          val = linear(time,key(n).time,mid,v1,v2)
        else
          val = linear(time,mid,key(n+1).time,v2,v1);
      }
    }
  }
}
val

[Steven Kent27869994kodo]

Thank you so much Dan! This works.