How to create a looping animation that randomly selects images to appear in a set position

[Namder-K]

Hi, I'm looking to create a looping animation that randomly selects images to appear in a set position - no scaling or moving, purely images that will randomly replace each other.

In this instance I have 20 faces, all the same size. The idea is for the faces to constantly change and be randomly replaced by one of the other faces, in an endless loop. Each instance would be for a set period of time - always .1 seconds.

Assuming this will be an expression that I'm not smart enough to figure out - thank you!

[Dan Ebberts · Accepted solution]

Here's a simple example. You could have a null layer named "Control" at the bottom of your layer stack with a slider control with this expression:

n = thisComp.numLayers-1;
dur = .1;
seedRandom(Math.floor(time/dur),true);
Math.floor(random(n))+1

All your face layers would be at the top of the layer stack, each with this opacity expression:

idx = thisComp.layer("Control").effect("Slider Control")("Slider");
index == idx ? 100 : 0

Hopefully that gets you headed in the right direction.

[Dan Ebberts]

BTW, if you need to ensure that the same face doesn't come up twice in a row, you could switch to this for the control layer's slider expression:

n = thisComp.numLayers-1;
dur = .1;
seg = Math.floor(time/dur);
seedRandom(index,true);
idx = Math.floor(random(n));
for (i = 0; i <= seg; i++){
  idx += Math.floor(random(1,n-1));
  idx %= n;
}
idx+1

[Namder-K]

This worked perfectly, thank you so much Dan - appreciate it!