How to create this?

[Sergio Cabrera]

You could do it in Photoshop, make the left half of the spectrum with a line and curves, and then mirror the right side by copying/paste/flip horizontally so it’s perfectly symmetric, then import to AE.

[Rick Andes]

Thanks Sergio. Do you mean importing a PNG/JPG file from Photoshop and create a Mask with Auto Trace? I tried this workflow but there are two main problems:
2) This function creates an outline mask (contour). I need a single line path instead of a contour.
1) It loses functionality. For example: I can’t change colors afterwards

Maybe a different workflow?

[Garrett Appleton]

Pen tool the shape in AE then “trim path” animate the shape. This might be your best option. There are also ae plugins on https://aescripts.com/ if you want a faster method. But trim paths is my favorite way to animate a path change. You can manipulate the start and end to make it look like the straight line is disappearing as the waveform is being drawn. Just a heads up, where you start to draw your path is where the “Trim Path” property choses as the start of the animation.

Garrett Appleton
Motion Design | Compositor | Dev
Apetown Art

[Oleg Pirogov]

My shot:
1) Create a null
2) Add this code to position expression:
X=linear(time, 0, 60,-(6+0.5)*Math.PI, (6+0.5)*Math.PI);
Y=linear(time, 0, 60,0,Math.PI);
f=100*Math.cos(X)*Math.sin(-Y);
[value[0]+10*X, value[1]+f];
– this creates something close to the wavy thing from your post and applies it to the motion path
3) Convert expression to keyframes
4) Add one key at the start and one at the end of the sequence and manually reposition null at those keys to make flat tails
5) Create a shape layer with some path and copypaste null’s motion path keyframes to the path property

Gets you this:

[Rick Andes]

Thanks a lot Oleg!

One problem remaining. I copied the keyframes to a path as you suggested, including the two extra keypoints (see screenshot #1). The wave must emerge from a flat line, so I added two extra path keyframes with a flat line.

The wave emerges from the left instead of the center. How can I fix this?

Screenshot 1

Screenshot 2