[WorldWind学习]3.Device对象

　　首先介绍一下Device类，Device位于using Microsoft.DirectX.Direct3D;命名空间下。

　　Device类用于完成DirectX 里所有绘图操作，我们可以把这个类假想为图形卡，场景里所有其他图形对象都依赖于Device，计算机里可以有多个Device对象。所以在全局变量中定义一个绘图设备，如下代码：
　　private Device m_Device3d;//定义绘图设备　 

private void InitializeGraphics()
        {
            // Set up our presentation parameters
            m_presentParams = new PresentParameters();

            m_presentParams.Windowed = true;//指定以Windows窗体形式显示
            m_presentParams.SwapEffect = SwapEffect.Discard;//当前屏幕绘制后
它将自动从内存中删除 
            m_presentParams.AutoDepthStencilFormat = DepthFormat.D16;//深度检测
            m_presentParams.EnableAutoDepthStencil = true;
            
            if(!World.Settings.VSync)
                // Disable wait for vertical retrace (higher frame rate at the expense of tearing)
                m_presentParams.PresentationInterval = PresentInterval.Immediate;

            int adapterOrdinal = 0;
            try
            {
                // Store the default adapter
                adapterOrdinal = Manager.Adapters.Default.Adapter;
            }
            catch
            {
                // User probably needs to upgrade DirectX or install a 3D capable graphics adapter
                throw new NotAvailableException();
            }

            DeviceType dType = DeviceType.Hardware;

            foreach(AdapterInformation ai in Manager.Adapters)
            {
                if(ai.Information.Description.IndexOf("NVPerfHUD") >= 0)
                {
                    adapterOrdinal = ai.Adapter;
                    dType = DeviceType.Reference;
                }
            }
            CreateFlags flags = CreateFlags.SoftwareVertexProcessing;

            // Check to see if we can use a pure hardware m_Device3d
            Caps caps = Manager.GetDeviceCaps(adapterOrdinal, DeviceType.Hardware);

            // Do we support hardware vertex processing?
            if(caps.DeviceCaps.SupportsHardwareTransformAndLight)
                //    // Replace the software vertex processing
                flags = CreateFlags.HardwareVertexProcessing;

            // Use multi-threading for now - TODO: See if the code can be changed such that this isn't necessary (Texture Loading for example)
            flags |= CreateFlags.MultiThreaded | CreateFlags.FpuPreserve;

            try
            {
                // Create our m_Device3d   实例化device对象
                m_Device3d = new Device(adapterOrdinal, dType, this, flags, m_presentParams);
            }
            catch( Microsoft.DirectX.DirectXException    )
            {
                throw new NotSupportedException("Unable to create the Direct3D m_Device3d.");
            }

            // Hook the m_Device3d reset event
            m_Device3d.DeviceReset += new EventHandler(OnDeviceReset);
            m_Device3d.DeviceResizing += new CancelEventHandler(m_Device3d_DeviceResizing);
            OnDeviceReset(m_Device3d, null);
        }