After Effects expression, for scaling a layer 10% over 1 sec, on a slider value.

[Dan Ebberts]

How are you animating the slider value, and how will the expression know which slider value it needs to respond to?

[Juan Carlos aguirre]

The animation slider its a bit complicated since I have 2 variables, “frame” that its the raw position of my photo, and “fine” that its a fine tune to center

var frame = effect(“Frame”)(“Slider”);

var fine = effect(“fine”)(“Slider”)

{p= (frame * -1663) + fine};

[p]

The slider control for the frame is the one I need to link as a target to start the scale-up.

Exp: If(“Frame”)(“Slider”) = 10, then scale up this layer 10% over xx seconds, then scale down.

The slider is on a different comp, but I can find out how to link it.

Let me know if this makes sense.

Or I can share my project if needed.

[Dan Ebberts]

It sounds like it might be pretty much the worst case scenario, where you have to use the brute force, frame-by-frame method to find the trigger event. This is a simple example where the expression needs to find when the slider has reached its ID value (which is 10 in this example) and will scale up, hold, and scale down from that point:

slider = thisComp.layer("Controls").effect("Slider Control")("Slider");
myID = 10;
scaleMult = 1.1;
scaleUpTime = 1.0;
holdTime = 1.0;
scaleDnTime = 1.0;
if (slider.value >= myID){
  t = time;
  while (slider.valueAtTime(t) >= myID){
    t -= thisComp.frameDuration;
  }
  deltaT = time - t + thisComp.frameDuration;
  if (deltaT > scaleUpTime + holdTime + scaleDnTime){
    value;
  }else if (deltaT > scaleUpTime + holdTime){
    linear(deltaT,scaleUpTime + holdTime, scaleUpTime + holdTime + scaleDnTime,value*scaleMult,value);
  }else if (deltaT > scaleUpTime){
    value*scaleMult;
  }else{
    linear(deltaT,0,scaleUpTime,value,value*scaleMult);
  }
}else
  value

It assumes that the slider value always increases. The longer your comp is, the worse the performance will get. Hopefully this will get you started.

[Juan Carlos aguirre]

Awesome, Thank you, Dan.

Jumping to it, now.

I assume that the scale and hold variables could also be linked to another slider control right.

Then I can make global adjustments.

I’ll try and keep you posted.

JC.