Using a set of corners of a solid that lie in a plane to form the polygon vertices of a new polygon is called faceting. Such polygons may outline new faces that join to enclose a new solid, even if the sides of the polygons do not fall along polygon edges of the original solid.
Faceting
Explore with Wolfram|Alpha
References
Holden, A. Shapes, Space, and Symmetry. New York: Columbia University Press, p. 94, 1971.Referenced on Wolfram|Alpha
FacetingCite this as:
Weisstein, Eric W. "Faceting." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Faceting.html