Topology Primitives

Topology primitives consist of nodes, edges, and faces.

Each primitive has references to features that allow navigation between topology and features used during topology structuring. For example, the reference area_to_face is used during structuring to find the faces that comprise a polygon.

Topology information is calculated by a Build Topology task and stored within a datastore containing internal classes. The classes for topology are sys:node, sys:edge and sys:face. When you build topology, these classes are populated. 

There is only one set of topology primitives per session. To have different sets of topology primitives, you need different sessions with their own Build Topology task.

At the end of the session, the topology primitives are thrown away, unless you create an action to copy some or all of them to your own classes (for example copying face geometries for a polygonisation action).