Euler boolean operation

In constructive solid geometry, an Euler boolean operation is a series of modifications to solid modelling which perserves the Euler characteristic in the boundary representation at every stage. One or more of these Euler boolean operations is stored in a change state, so as to only represent models which are physically realizable.

Failing to to maintain the Euler characteristic would result in geometric and topological entities often depicted by M. C. Escher. Esher's geometry artwork comes close to perserving the Euler characteristic (usually a problem with just the hole count).