WinForm Elementhost with WPF doesn´t show 3d Graphic

Hello,

i do have following Code on a winform:

Code:

---

using System;
using System.Windows.Forms;
using System.Windows.Forms.Integration;

using wpf = System.Windows.Controls;
using wpfpaint = System.Windows.Media;
using System.Windows.Media.Media3D;

namespace WindowsForms_WPF_3
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            FormBorderStyle = FormBorderStyle.Fixed3D;
           
            // Elemethost für wpf-Control definieren

            ElementHost eh = new ElementHost();
            eh.Dock = DockStyle.Fill;
            this.Controls.Add(eh);


            //wpf-Control DockPanel definieren und der Eigenschaft child des Elementhost zuordnen

            wpf.DockPanel dp = new wpf.DockPanel();
            dp.Background = wpfpaint.Brushes.LightGray;
            eh.Child = dp;


            // wpf-Viewport3D Element für die Anzeige von 3D-Gfrafiken definieren

            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, -1, 15);
            Vector3D lookDirection = new Vector3D(1, 1, 0);
            Vector3D upDirection = new Vector3D(0, 1, 0);
            double fieldOfView = 45;
            PerspectiveCamera camera = new PerspectiveCamera(position, lookDirection, upDirection, fieldOfView);

            vp3d.Camera = camera;

            // Licht definieren

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

            // Modell definieren

            MeshGeometry3D mesh = new MeshGeometry3D();
            Point3D[] points =
            {
                new Point3D(1, 1, 0), new Point3D(5, 1, 0), new Point3D(2.5, 5, 0)
            };

            foreach (Point3D point in points) mesh.Positions.Add(point);

            Tuple<int, int, int>[] triangles =
            {
                new Tuple<int, int, int>(0, 1, 2)
            };

            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 kreieren

            GeometryModel3D model = new GeometryModel3D(mesh, material);


            // Modell der Geometriegruppe zuweisen

            group3d.Children.Add(model);

            // wpf DockPanel zum Viewport 3D einfügen

            dp.Children.Add(vp3d);

        }
    }
}

---

I expect that it Shows a cube but it doesn´t - When i do the simular thing within an wpf-program it works.
So i do have some Questions:
1) It is possible to use ElementHost to draw 3Ds in this way?
2) what is the failure in the Code above?
3) Is there the same ccordinate-System?

best regards
Volkhard