WPF и ElementHost для WindowsForms не отображают графику

Question

Я хочу разместить wpf-canvas в классе формы windows для отображения 3d-quader. поэтому у меня есть следующий класс в проекте формы windows:

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            ElementHost eh = new ElementHost();
            eh.Dock = DockStyle.Fill;

            wpf.Canvas cv = new wpf.Canvas();
            //wpf.DockPanel dp = new wpf.DockPanel();

            cv.Background = wpfpaint.Brushes.Green;

            eh.Child = cv;

            this.Controls.Add(eh);


            Line myLine = new Line();
            myLine.X1 = 1;
            myLine.X2 = 50;
            myLine.Y1 = 1;
            myLine.Y2 = 50;
            myLine.Stroke = wpfpaint.Brushes.Black;
            myLine.StrokeThickness = 2;

            cv.Children.Add(myLine);


            wpf.Viewport3D vp3d = new wpf.Viewport3D();

            wpfpaint.Media3D.ModelVisual3D visual3d = new wpfpaint.Media3D.ModelVisual3D();
            wpfpaint.Media3D.Model3DGroup group3d = new wpfpaint.Media3D.Model3DGroup();

            visual3d.Content = group3d;
            vp3d.Children.Add(visual3d);

            // Kamera definieren

            Point3D position = new Point3D(1.5, 2, 3);
            Vector3D lookDirection = new Vector3D(-position.X, -position.Y, -position.Z);
            Vector3D upDirection = new Vector3D(0, 1, 0);
            double fieldOfView = 60;
            PerspectiveCamera camera = new PerspectiveCamera(position, lookDirection, upDirection, fieldOfView);

            vp3d.Camera = camera;

            // Licht definieren

            group3d.Children.Add(new AmbientLight(wpfpaint.Colors.Gray));
            Vector3D direction = new Vector3D(1, -2, -3);
            group3d.Children.Add(new DirectionalLight(wpfpaint.Colors.Gray, direction));


            // Modell definieren

            MeshGeometry3D mesh = new MeshGeometry3D();
            Point3D[] points =
            {
                new Point3D(-1, -1, -1), new Point3D(1, -1, -1),
                new Point3D(1, -1, 1), new Point3D(-1, -1, 1),
                new Point3D(-1, -1, 1), new Point3D(1, -1, 1),
                new Point3D(1, 1, 1), new Point3D(-1, 1, 1),
                new Point3D(1, -1, 1), new Point3D(1, -1, -1),
                new Point3D(1, 1, -1), new Point3D(1, 1, 1),
                new Point3D(1, 1, 1), new Point3D(1, 1, -1),
                new Point3D(-1, 1, -1), new Point3D(-1, 1, 1),
                new Point3D(-1, -1, 1), new Point3D(-1, 1, 1),
                new Point3D(-1, 1, -1), new Point3D(-1, -1, -1),
                new Point3D(-1, -1, -1), new Point3D(-1, 1, -1),
                new Point3D(1, 1, -1), new Point3D(1, -1, -1),
            };
            foreach (Point3D point in points) mesh.Positions.Add(point);

            Tuple<int, int, int>[] triangles =
            {
                 new Tuple<int, int, int>(0, 1, 2),
                 new Tuple<int, int, int>(2, 3, 0),
                 new Tuple<int, int, int>(4, 5, 6),
                 new Tuple<int, int, int>(6, 7, 4),
                 new Tuple<int, int, int>(8, 9, 10),
                 new Tuple<int, int, int>(10, 11, 8),
                 new Tuple<int, int, int>(12, 13, 14),
                 new Tuple<int, int, int>(14, 15, 12),
                 new Tuple<int, int, int>(16, 17, 18),
                 new Tuple<int, int, int>(18, 19, 16),
                 new Tuple<int, int, int>(20, 21, 22),
                 new Tuple<int, int, int>(22, 23, 20),
            };
            foreach (Tuple<int,int,int> tuple in triangles)
            {
                mesh.TriangleIndices.Add(tuple.Item1);
                mesh.TriangleIndices.Add(tuple.Item2);
                mesh.TriangleIndices.Add(tuple.Item3);
            }

            // Objektmaterial definieren

            DiffuseMaterial material = new DiffuseMaterial(wpfpaint.Brushes.LightBlue);

            // Modell creieren

            GeometryModel3D model = new GeometryModel3D(mesh, material);


            // Modell der Geometriegruppe zuweisen

            group3d.Children.Add(model);

            cv.Children.Add(vp3d);

        }

    }

Мой вопрос: почему отображается 2-я линия, а не квадер? если я реализую это в аналогичном wpf-проекте и wpf-окне, он показывает Quader.

Может ли кто-нибудь помочь?

с наилучшими пожеланиями

Volkhard