Adding a Camera to Your Scene
If you run the application, you notice that nothing looks different. You still see a black screen and nothing else. You have all the code in to load and render your sky box mesh, so why isn't it rendering? Direct3D doesn't know exactly what it can render yet. In a 3D scene, you need to include a camera so Direct3D knows which areas of the world it should render. Add the code in Listing 4.9 to the OnDeviceReset method now.
Listing 4.9. Setting Up a Camera
// Set the transformation matrices
localDevice.Transform.Projection = Matrix.PerspectiveFovLH(
(float)Math.PI / 4,
(float)this.Width / (float)this.Height, 1.0f, 1000000.0f);
localDevice.Transform.View = Matrix.LookAtLH(new Vector3(0,0,-54),
new Vector3(), new Vector3(0,1,0));
Here you set two transforms on the device that control the camera. The first is the projection matrix, which determines how the camera's lens behaves. You can use PespectiveFovLH method to create a projection matrix based on the field of view for a left-handed coordinate system (which is described later in Chapter 10, "A Quick 3D-Math Primer").
By default, Direct3D uses a left-handed coordinate system, so it is assumed from here on that you are as well. Direct3D can render in a right-handed coordinate system as well, but that topic isn't important for this book. Here is the prototype for the projection matrix function:
public static Microsoft.DirectX.Matrix PerspectiveFovLH (
System.Single fieldOfViewY ,
System.Single aspectRatio ,
System.Single znearPlane ,
System.Single zfarPlane )
The projection transform is used to describe the viewing frustum of the scene. You can think of the viewing frustum as a pyramid with the top of it cut off; the inside of the pyramid is what you can actually see inside your scene. The two parameters in the preceding function, the near and far planes, describe the limits of this pyramid, with the far plane making up the "base" of the pyramid structure and the near plane where you would cut off the top.
With the camera transforms set up, you might be wondering why you add the code to the OnDeviceReset method. The reason is that any time the device is reset (for any reason, such as being lost), all device-specific state is lost. This state includes the camera transformations. As a result, the OnDeviceReset method (which is called after the device has been reset) is the perfect place for the code.
You might also be wondering why you are using events, and why they would work, because earlier in this chapter you disabled the event handling. The event handling that you disabled was only the internal Direct3D event handling. The events are still fired and are available for you to consume if needed.
Remember from earlier, you can't rely on the event handlers to automatically clean up your objects for you. You need to make sure you dispose of these new items you've created when the application shuts down. It's important to clean up these objects because failure to do so results in memory leaks, which can cause system instability and poor performance. Although the garbage collector can (and does) handle much of this memory management for you, doing this cleanup here will give you much finer control over the resources the system is using. Add the following code to your OnDestroyDevice method:
// Clean up the textures used for the mesh level
if ((levelTextures != null) && (levelTextures.Length > 0))
{
for(int i = 0; i < levelTextures.Length; i++)
{
levelTextures[i].Dispose();
}
// Clean up the mesh level itself
levelMesh.Dispose();
}
This code ensures each of the textures and the mesh are cleaned up. You must add any resource that you create to this method for cleanup.
|
