Polylines and spatial polygons

A polyline in three-dimensional space is a sequence of points $A_1, A_2, ..., A_n$ where each consecutive pair $(A_i, A_{i+1})$ is joined by a straight segment. A spatial polygon is a polyline where $A_n = A_1$, forming a closed loop. Unlike plane polygons, the points do not all have to lie in the same plane.

Important properties

• Polylines can be open (ends do not meet) or closed (ends meet).

• A spatial polygon is a closed polyline in space.

• Spatial polygons may not be planar; their vertices can be in different planes.

• The length of a polyline is the sum of the lengths of its segments.