A multisheet plane figure and its medial axis

A multisheet plane figure is a projection onto the plane of a surface whose every point has a neighborhood which can be projected onto the plane univocally. A multisheet plane figure can be considered as a generalization of the concept of a common plane figure for the case when the boundary may contain self-intersecting curves and pairwise intersecting curves. The medial axis of a common plane figure is a set of points equidistant from the boundary. The concept of the medial axis of a multisheet plane figure is defined and researched into in the paper. Medial axis can be utilized in numerous computer science applications.