How to make a shape change over time in After Effects

How do you make a shape change over time in Adobe After Effects, let’s say from a circle to a triangle?

How to make a shape change over time in After Effects

This can, in some cases, be very easy to do, depending on the shapes.
In this example, we have two layers with one shape in each layer, a circle and a triangle.

Start by opening one layer, go to “Contents”, “Ellipse 1”, “Ellipse Path 1” and right-click on it. Click “Convert To Bezier Path” and now do the same thing with the other layer.

Now open “Path 1” on the top layer and click the stopwatch next to “Path” to create a keyframe. Also click the stopwatch next to the other properties that will change, in this case “Anchor Point” and “Position”.
Then click keyboard shortcut “U” to hide the remaining properties for now.
And then do the same process with the other Shape layer.

Then copy the “Path”-keyframe from the shape you want it to change to with “cmd/ctrl + C”, click the text “Path” of the other shape, move the playhead to the right and paste with “cmd/ctrl + V”.
Then, with the playhead in that position, do the same thing with “Anchor Point” and “Position”.

Now, when you play it from the start you can see that it changes from a circle to a…