Faces

Faces exist in planar topology only and represent the interior of an area formed by enclosing edges. A polygon is represented by one or more faces.

The edges describe the outer and inner boundaries of the face geometry and any edges contained by, but not bounding, the face.

To ensure that faces never overlap, edges cannot cross edges. If an edge does cross another edge, a node is created at the junction and each edge is split into two edges.

Adjacent faces share an edge, but the edge is used in opposite directions.

Note: In the example diagram above, f0 is a universe face (sys:is_universe_face) that  surrounds all other faces. When creating rules and actions the universe face is often ignored.

A face class has the following references:

• sys: face_to_edge - Obtains all edges on the boundary of a face
• sys: face_to_node - Obtains all isolated nodes within the face

Faces can also use sys:area_to_face reference on any polygon features that use the face.