A polygon is a type of Primitive that is formed from a set of Vertices in 3D that are implicitly connected together to form a multi-edge shape. Each Vertex is a reference to a Point in a Point List. Polygons in a Primitive List are part of the Geometry Detail, which is a part of a SOP.
Types of Polygons
- Closed or Open
A polygon can be closed, where the last vertex is connected to the first vertex, or may be open, where the last vertex is not connected to the first vertex. This is determined by the "closed" flag of a polygon.
A closed polygon shares its first and last vertex and is flagged internally as "closed". Thus, if an open polygon has five vertices, it will still have five vertices when closed. The last (closing) vertex is only implied.
- Planar or Non-planar
Planar polygons are those whose vertices lie in the same plane in 3D space. Non-planar polygons have vertices that do no lie in the same plane in 3D space.
- Convex or Concave
A polygon can be convex or concave, as illustrated below:
A polygon is convex if any vertical or horizontal axis intersects it at most twice.