Dear Friends, I forgot the vertices for triangulated mesh.
we know for each mesh face we have 0,1, 2, 3 vertices.
pt1 for vertex 
pt2 for vertex 
pt3 for vertex 
but I forgot about pt4, is it vertex1 for triangulated mesh?
i mean 1st and 4th vertex should be same for triangulated mesh… am I correct?
MeshFace mface = F_LIST.GetFace(i);
Point3f pt1 = new Point3f();
Point3f pt2 = new Point3f();
Point3f pt3 = new Point3f();
Point3f pt4 = new Point3f();
mmesh.Faces.GetFaceVertices(i, out pt1, out pt2, out pt3, out pt4);