The Schlegel diagram shows the network of edges and vertices of any
"convex hull" (as mathematicians would put it) by projecting the object
onto a two-dimensional plane surface. (Visualize the shadow pattern
projected by a point light source.) It is a convenient way to
visualize the bonding network of fullerenes. This movie (created
using pov-ray) shows a light
source being "lowered" almost into the "top" pentagonal face of a
C70 molecule, generating a symmetrical shadow pattern
having the same connectivity as the three-dimensional bonding
network.