WORKING WITH 3D GRAPHICS IN WPF in Font

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contains point1, and so on. Had these been added out of order, then the indices would not be smart enough to figure out the correct values. Thus, the moral of the story is to be careful about the order in which you add your points! You can calculate a normal if you want, or you can just define one manually. In this example, you will define one manually as running along the Y axis like this: Vector3D normal = new Vector3D(0, 1, 0); Then, you add the normal vector to the Normals collection for the mesh: triangleMesh.Normals.Add(normal); To build the model of the triangle, you need the mesh (which you have now finished defining) and the material that defines how the mesh will be painted. You want a red triangle so you ll build a simple red Material object like this: Material material = new DiffuseMaterial( new SolidColorBrush(Colors.Red)); You can do lots more complex things with materials, but you will stick with a simple SolidColorBrush for now. You are now ready to create the model of your triangle that WPF can understand and render. You do this by creating a GeometryModel3D using the mesh and the material and then using this to fill the content of a ModelVisual3D object like this: GeometryModel3D triangleModel = new GeometryModel3D( triangleMesh, material); ModelVisual3D model = new ModelVisual3D(); model.Content = triangleModel; Finally, you add the model to the ViewPort3D object for rendering to occur: this.vpt.Children.Add(model); Listing 9-3 shows the complete code. Listing 9-3. Defining a Triangle using System.Windows.Media.Media3D; public Window1() { InitializeComponent(); MeshGeometry3D triangleMesh = new MeshGeometry3D(); Point3D point0 = new Point3D(0, 0, 0); Point3D point1 = new Point3D(2, -4, 0); Point3D point2 = new Point3D(0, 0, 5); triangleMesh.Positions.Add(point0); triangleMesh.Positions.Add(point1); triangleMesh.Positions.Add(point2); triangleMesh.TriangleIndices.Add(0); triangleMesh.TriangleIndices.Add(2);

triangleMesh.TriangleIndices.Add(1); Vector3D normal = new Vector3D(0, 1, 0); triangleMesh.Normals.Add(normal); Material material = new DiffuseMaterial( new SolidColorBrush(Colors.Red)); GeometryModel3D triangleModel = new GeometryModel3D( triangleMesh, material); ModelVisual3D model = new ModelVisual3D(); model.Content = triangleModel; this.vpt.Children.Add(model); } When you run this application, you ll see the results shown in Figure 9-6.

You use a ViewPort3D object to create the 3D scene. This control displays 3D content and provides properties for controlling that content such as clipping, height, width, and response to mouse events. The object contains a number of property classes that are used to dictate this behavior; you will look at some of those classes in the following sections.

Earlier you set up the XAML code for the ViewPort3D object, which included the definition of the camera that would provide the user s viewpoint on the scene. The camera specifies which part of the 3D scene is viewable. The PerspectiveCamera type is the most realistic of these; it s like a real camera, where the viewing surface is a single point, and it describes a viewing pyramid, with the far plane of viewing being the base of the pyramid and the camera being the apex of the pyramid viewing everything between it and the distant plane using a method called perspective foreshortening. Another type of camera is the OrthographicCamera type, which performs a

parallel projection of the 3D objects onto the 2D surface. In real-world terms, a perspective camera works similarly to a photographic camera, and an orthographic projection works similarly to you looking out a window at an object. To set up a PerspectiveCamera, first you need to specify where the camera is you do this using the Position property to specify where it is in 3D coordinate space. For example, if the camera is to be at position 1 on the X axis and 0 on Y and Z, you would specify its position as {1,0,0}. Then, you need to specify the distance to the far plane of viewing (that is, how far the camera can see). This is an absolute distance from the camera, not a coordinate in space. For example, if your camera is looking along the X axis and is positioned at point 1 on this axis (that is, {1,0,0}) and the far plane distance is 100, then the far plane of viewing will be intersecting the X axis at { 99,0,0}. Next, you need to specify the direction in which the camera is looking. If you consider the camera to be at a single point in 3D space, the direction it is looking in is a vector originating at that point. You specify the direction by specifying to which point the camera should look. So, if you look at the following XAML, you will see that the camera is at {10,10,10} and is looking at { 10, 10, 10} with the far plane distance being 100 units away. So if any other objects were in the scene behind the triangle, you would see them, unless they were farther than 100 units away. Here s the XAML: <Viewport3D.Camera> <PerspectiveCamera FarPlaneDistance="100" LookDirection="-10,-10,-10" Position="10,10,10" /> </Viewport3D.Camera> You can use a plethora of other properties on a perspective camera that may be useful, such as the field of view, which allows you to specify (in degrees) the width of the field of view available into which to project. For example, if you see the camera as the tip of a pyramid, with the base being the far plane, you specify the width of the pyramid using the field of view. A narrow field of view will give you a tall, thin pyramid, and a wide field of view will give you a short, fat one. You can also specify and use the camera in code. Thus, you can manipulate your camera to move it around the scene and make things more interesting. Here s an example of how you would create the same camera using C#: PerspectiveCamera pCam = new PerspectiveCamera(); pCam.FarPlaneDistance = 100; pCam.Position = new Point3D(10, 10, 10); pCam.LookDirection = new Vector3D(-10, -10, -10); vpt.Camera = pCam; this.vpt.Children.Add(model); Thus, you can manipulate the camera using code also. Here is an example of a small routine that changes the X position of the camera, which could be used on a mouse click or other event handler: