Seamless Morph between Circle, Rectangle and Triangle

,

Hello everyone

I am currently testing different methods of morphing simpel shapes into each other.
With the rectangle TOP is really easy to go from Circle to Rectangle, but triangle is still tricky.

One method I tried was to animate the parameter “sides” of a circle
Problem is the large jumps from triangles to rectangles.

The other solution came from a tutorial I saw:

Unfortunately it only works with SOPs and not with TOPs and only makes Outlines and no filling.

Somebody any smart ideas how to solve the problem?