4.1. Determination of vertices VNE and VSWIf there are ms vertices and ns edges in the parting lines PL, the two vertices that meet equations (1) and (2) respectively can be determined. If the vertex meets equa- tion.(1), the vertex will be located at the most north-eastern (NE) region in the projected contour as shown in figure 7. It is called the north-eastern vertex and can be denoted by VNE: