Cause: The geometry did not start from the correct level in the hierarchy.

Action: Correct the hierarchy in the geometry.

Cause: The geometry contained one or more unexpected holes.

Action: Remove any holes in the geometry.

Cause: The solid geometry was not closed i.e., faces of solid are not 2-manifold due to incorrectly defined, oriented, or traversed line segment because each edge of a solid must be traversed exactly twice, once in one direction and once in the reverse direction.

Action: Correct the orientation of the edges of the neighboring polygons.

Cause: The orientation of the solid was not correct.

Action: Correct the orientation or specification of the outer or inner solid geometry according to the geometry rules for such a solid.

Cause: The geometry contained more than one outer geometry.

Action: Remove all but one of the outer geometries.

Cause: The ring was not flat.

Action: Make sure all of the vertices of the ring are on the same plane.