Truncation (InstanceTopic, 3)

From Hi.gher. Space

Truncation is the process of cutting polytope facets to produce new polytopes. The kind of truncation can be specified by a Dx number.

Particular types of truncation include:

Mesotruncation

Truncates the polytope to its "midpoint". In odd dimensions, this is represented as the middle Coxeter-Dynkin node ringed. In even dimensions, the middle two nodes are ringed.

Peritruncation

"Expands" the polytope. This is represented with the first and last nodes ringed. Etymology: the Romanian for "outside" is "periferic" - you can imagine the ringed nodes as being on the "outside" (at the ends) of the diagram.