Here is a code snippet which allows you to animate text changes similar to a split-flap display using AfterEffects. The animation does not look exactly like those displays because I wanted a slightly different behavior for texts of different lengths. This is how the effect will look like (click on the following image to start the animation):

So how to do this in AfterEffects?

1. Create a new text layer and add a slider control to the layer by searching for it in the Effects&Presets field.
2. Now we have to enter an expression for the source text: open the layer properties and then the text property. Alt-click on the stop watch next to “Source Text”. Now, it should look like this:
3. Then enter the following code into the expression field (the field on the right which currently says “text.sourceText”):

   var oldText = "the old text";
   var newText = "new content";
   
   
   var result = "";
   var percentage = Math.min(Math.max(0,<code>effect("Slider Control")("Slider"</code>),100);
   //Iterate through charcodes
   var maxLength = Math.max(oldText.length, newText.length);
   for(var i=0; i<maxLength; i++) {
   	if(i> oldText.length-1) {
   		//The old text is shorter
   		var toomuch= maxLength-oldText.length;
   		var additional = percentage/100*toomuch;
   		if(i < oldText.length+ additional) {
   			result += String.fromCharCode(newText.charCodeAt(i));
   		}
   	} else if( i > newText.length-1) {
   		//The new text is shorter
   		var toomuch= maxLength-newText.length;
   		var additional = (100-percentage)/100*toomuch;
   		if(i < newText.length+ additional) {
   			result += String.fromCharCode(oldText.charCodeAt(i));
   		}
   	} else {
   		result += String.fromCharCode(oldText.charCodeAt(i) + percentage/100*(newText.charCodeAt(i)-oldText.charCodeAt(i)));
   	}
   }
   result
   
   

4. Note: if you have started AfterEffects in a different language than English you will get an exception. This is because effect("Slider Control")("Slider") in line 5 cannot be found. Find the slider control in the text layer, write down the right names and enter them into line 5 (i.e. in German: effect("Einstellungen für Schieberegler")("Schieberegler") ).
5. Change the variables oldText and newText to your desired values.
6. Now you can animate the slider with values between 0 (old text) and 100 (new text).

You can also download an example project:

AE SplitFlap animation example

1 file(s) 73.58 KB

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