A solid is a planar entity that determines a rectangular solid area. A solid
is a planar object. All vertices of a solid are located in the same plane and
are specified by two coordinates: x and y (z is the same for all vertices).
A solid's plane can be oriented in world space in any direction. Orientation
of a trace's plane is normal to the plane.
For working with solids, use the OdDbSolid class, which represents a solid
and allows users to access a solid entity and manipulate its properties. The
OdDbSolidPtr class is the typified smart pointer to an instance of this entitiy,
and it is used for storing and passing references to the solid objects.