Tweening between one and many polygons with an approach that’s faster and more robust than this Voronoi jigsaw attempt.
This approach uses earcut and some artisanal TopoJSON to triangulate the polygon and successively merge the triangles into the desired number of pieces, and then adds/rewinds points for smoother transitions (see this demo for a better look at what’s happening behind the scenes).
See also: Triangulation morphing, Jigsaw morphing, Smoother polygon transitions