When you watch the animation, you could say: "Well, that's done using a single switch layer, using interpolation!" And you'd be wrong. This is done using three switch layers.
I drew a box and a panel in separate vector layers, with different numbers of points. Next, I created a copy of each vector layer, rearranged the pixels for each copy into a kind of in-between form, and made sure both vector layers looked alike.
So I had four vector layers:
- layer A
- modified layer A
- layer B
- modified layer B
Next, I created the following layers setup, with switch interpolation turned on:
+- Switch A/B
+---- Switch A / mod A
+------- layer A
+------- layer mod A
+---- Switch B / mod B
+------- layer B
+------- layer mod B
Now it is possible to transform one shape into another, even a possible triangle into an impossible one: