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• How to create a looping animation that randomly se...

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

New Here ,
Apr 19, 2021 Apr 19, 2021

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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!

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Expressions , How to , Scripting

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Community Expert , Apr 19, 2021 Apr 19, 2021

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.

4 Replies 4
Community Expert ,
Apr 19, 2021 Apr 19, 2021

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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.

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Community Expert ,
Apr 19, 2021 Apr 19, 2021

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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``````

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New Here ,
Oct 26, 2023 Oct 26, 2023

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This is exactly what iv been looking for thanks!
I have one additional request, How would i now fade each random face to the next instead of just snapping?

So like a specified fade out time between each face, and would that go in each of the face layers or the control null layer?
Thank you

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New Here ,
Apr 20, 2021 Apr 20, 2021

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