Above left: Leonardo da Vinci supplied two
views: a plane view and an empty view where he removes the sides to
reveal the complete structure of the octahedron. Above right: an
octahedron was created using computer program Jenn 3D.
Leonardo da Vinci (1452-1519) was a great lover of geometry. His
most outstanding polyhedral accomplishment is the illustrations for Luca
Pacioli's 1509 book The Divine Proportion.
Jenn 3D is a free software license program for visualizing
regular polytopes in stereographic projection. Capabilities include: a
large database of Coxeter polytopes, 6-axis motion control, animation,
fly-though, stereo viewing, high-res capture, depth-blur, camera, and
many style options.