Every point in the vector data has three coordinates - x, y, z. If this is enough for the point description, then the point is defined by the simple structure IGVectPoint3D. The examples of such points are: start and end point of the easy line, the point of the easy surface, minimum and maximum coordinates of the viewport. But often the point must have some additional attributes. They are: visibility, bulge and thickness of the outgoing line or the weight if the point belongs to the NURBS curve or surface. In these cases the point is represented by the Vertex structure IGVectVertex. Vertexes are created and owned by the Vertex Container. The Vertex container controls all additional Vertex attributes.