Example: Tetrahedron with vertex and edge topology labels. Assume vertex V3 is farthest from the reader.

The corresponding topology tree follows with surface, curve, and point geometry attached to face, edge, and vertex topology, respectively. Note that each edge appears twice; once with a forward and once with a reverse orientation with respect to the two owning loops. Loop directions follow the rule that the face is to the left of the loop when `up' is in the direction of the face normal.

    SOLID
        SHELL
        |
        +-- FACE1 (plane)
        |       LOOP
        |           FIN
        |               EDGE1-forward (line)
        |                   VERTEX1 (point)
        |                   VERTEX2 (point)
        |               EDGE3-forward (line)
        |                   VERTEX2 (point)
        |                   VERTEX3 (point)
        |               EDGE2-forward (line)
        |                   VERTEX3 (point)
        |                   VERTEX1 (point)
        +-- FACE2 (plane)
        |       LOOP
        |           FIN
        |               EDGE1-reverse (line)
        |               EDGE6-forward (line)
        |                   VERTEX1 (point)
        |                   VERTEX4 (point)
        |               EDGE4-forward (line)
        |                   VERTEX4 (point)
        |                   VERTEX2 (point)
        +-- FACE3 (plane)
        |       LOOP
        |           FIN
        |               EDGE6-reverse (line)
        |               EDGE2-reverse (line)
        |               EDGE5-forward (line)
        |                   VERTEX3 (point)
        |                   VERTEX4 (point)
        +-- FACE4 (plane)
        |       LOOP
        |           FIN
        |               EDGE4-reverse (line)
        |               EDGE5-reverse (line)
        |               EDGE3-reverse (line)

In the brief example above, attached curve `senses' are unspecified but essential to make a body. Curve sense is forward if the curve parameterization goes from the owning edge's 1st vertex to the 2nd vertex.