A polyhedral torus
A polyhedron that represents a surface of genus 1 (a torus), that can be thought as a doughnut, or as a sphere with one handle attached.
For this polyhedron, Euler's relation doesn't hold. Instead, we have Vertices - Edges + Faces = 0
© matematita
The image belongs to the sections...:
The torus (Topology)
Polyhedra of positive genus (3D geometry)
