实时3D地形引擎——Chapter6_02——D3DApp框架阅读1

下面就是入口点，这一次我们将从入口点开始分析一下D3DApp框架的运行过程。

//-----------------------------------------------------------------------------
// Name: WinMain()
// Desc: Entry point to the program. Initializes everything, and goes into a
//       message-processing loop. Idle time is used to render the scene.
//-----------------------------------------------------------------------------
INT WINAPI WinMain (HINSTANCE hInst, HINSTANCE, LPSTR, INT)
{
	cMyHost d3dApp;

	srand(timeGetTime());

	//  InitCommonControls();
	if (FAILED (d3dApp.Create (hInst)))
	 return 0;

	INT result= d3dApp.Run();

	cCodeTimer::RootTimer.outputAllTimers(0xffffffff);

	return result;
}

第一句就是新建了一个cMyHost对象d3dApp。而cMyHost的构造函数是空的，主要是在父类中做参数的初始化。

那么下一句就是d3dApp.Create(hInst)了。

HRESULT CD3DApplication::Create( HINSTANCE hInstance )
{
    HRESULT hr;

    // Create the Direct3D object
    m_pD3D = Direct3DCreate9( D3D_SDK_VERSION );
    if( m_pD3D == NULL )
        return DisplayErrorMsg( D3DAPPERR_NODIRECT3D, MSGERR_APPMUSTEXIT );

    // Build a list of Direct3D adapters, modes and devices. The
    // ConfirmDevice() callback is used to confirm that only devices that
    // meet the app's requirements are considered.
    m_d3dEnumeration.SetD3D( m_pD3D );
    m_d3dEnumeration.ConfirmDeviceCallback = ConfirmDeviceHelper;
    if( FAILED( hr = m_d3dEnumeration.Enumerate() ) )
    {
        SAFE_RELEASE( m_pD3D );
        return DisplayErrorMsg( hr, MSGERR_APPMUSTEXIT );
    }

    // Unless a substitute hWnd has been specified, create a window to
    // render into
    if( m_hWnd == NULL)
    {
        // Register the windows class
        WNDCLASS wndClass = { 0, WndProc, 0, 0, hInstance,
                              LoadIcon( hInstance, MAKEINTRESOURCE(IDI_MAIN_ICON) ),
                              LoadCursor( NULL, IDC_ARROW ),
                              (HBRUSH)GetStockObject(WHITE_BRUSH),
                              NULL, _T("D3D Window") };
        RegisterClass( &wndClass );

        // Set the window's initial style
        m_dwWindowStyle = WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_THICKFRAME | 
                          WS_MINIMIZEBOX | WS_MAXIMIZEBOX | WS_VISIBLE;

        // Set the window's initial width
        RECT rc;
        SetRect( &rc, 0, 0, m_dwCreationWidth, m_dwCreationHeight );
        AdjustWindowRect( &rc, m_dwWindowStyle, true );

        // Create the render window
        m_hWnd = CreateWindow( _T("D3D Window"), m_strWindowTitle, m_dwWindowStyle,
                               CW_USEDEFAULT, CW_USEDEFAULT,
                               (rc.right-rc.left), (rc.bottom-rc.top), 0,
                               LoadMenu( hInstance, MAKEINTRESOURCE(IDR_MENU) ),
                               hInstance, 0 );
    }

    // The focus window can be a specified to be a different window than the
    // device window.  If not, use the device window as the focus window.
    if( m_hWndFocus == NULL )
        m_hWndFocus = m_hWnd;

    // Save window properties
    m_dwWindowStyle = GetWindowLong( m_hWnd, GWL_STYLE );
    GetWindowRect( m_hWnd, &m_rcWindowBounds );
    GetClientRect( m_hWnd, &m_rcWindowClient );

    if( FAILED( hr = ChooseInitialD3DSettings() ) )
    {
        SAFE_RELEASE( m_pD3D );
        return DisplayErrorMsg( hr, MSGERR_APPMUSTEXIT );
    }

    // Initialize the application timer
    DXUtil_Timer( TIMER_START );

    // Initialize the app's custom scene stuff
    if( FAILED( hr = OneTimeSceneInit() ) )
    {
        SAFE_RELEASE( m_pD3D );
        return DisplayErrorMsg( hr, MSGERR_APPMUSTEXIT );
    }

    // Initialize the 3D environment for the app
    if( FAILED( hr = Initialize3DEnvironment() ) )
    {
        SAFE_RELEASE( m_pD3D );
        return DisplayErrorMsg( hr, MSGERR_APPMUSTEXIT );
    }

    // The app is ready to go
    Pause( false );

    return S_OK;
}

代码的注释非常详细，不过DX9初始化感觉有点麻烦。

1.ChooseInitialD3DSettings函数主要完成的功能是设置全屏和窗口模式。

2.DXUtil_Timer用来设置时间，这个函数可以用来完成有关时间的操作。

3.在D3DApp框架中，OneTimeSceneInit函数基本没用，需要子类重写来完成所需要的初始化。这一篇主要还是以D3DApp为主，因此就不看cGameHost的实现了。

4.Initialize3DEnvironment，初始化3D环境，完成的就是创建设备这类DX9初始化必需的步骤。

再次回到入口点函数，下一句就是d3dApp.Run()。这一次我们依然只看D3DApp中完成的事。

INT CD3DApplication::Run()
{
    // Load keyboard accelerators
    HACCEL hAccel = LoadAccelerators( NULL, MAKEINTRESOURCE(IDR_MAIN_ACCEL) );

    // Now we're ready to recieve and process Windows messages.
    bool bGotMsg;
    MSG  msg;
    msg.message = WM_NULL;
    PeekMessage( &msg, NULL, 0U, 0U, PM_NOREMOVE );

    while( WM_QUIT != msg.message  )
    {
        // Use PeekMessage() if the app is active, so we can use idle time to
        // render the scene. Else, use GetMessage() to avoid eating CPU time.
        if( m_bActive )
            bGotMsg = ( PeekMessage( &msg, NULL, 0U, 0U, PM_REMOVE ) != 0 );
        else
            bGotMsg = ( GetMessage( &msg, NULL, 0U, 0U ) != 0 );

        if( bGotMsg )
        {
            // Translate and dispatch the message
            if( hAccel == NULL || m_hWnd == NULL || 
                0 == TranslateAccelerator( m_hWnd, hAccel, &msg ) )
            {
                TranslateMessage( &msg );
                DispatchMessage( &msg );
            }
        }
        else
        {
            if( m_bDeviceLost )
            {
                // Yield some CPU time to other processes
                Sleep( 100 ); // 100 milliseconds
            }
            // Render a frame during idle time (no messages are waiting)
            if( m_bActive )
            {
                if( FAILED( Render3DEnvironment() ) )
                    SendMessage( m_hWnd, WM_CLOSE, 0, 0 );
            }
        }
    }
    if( hAccel != NULL )
        DestroyAcceleratorTable( hAccel );

    return (INT)msg.wParam;
}

这就是消息处理了，直到程序退出。消息处理其中一个重要地方在于渲染。

HRESULT CD3DApplication::Render3DEnvironment()
{
    HRESULT hr;

    if( m_bDeviceLost )
    {
        // Test the cooperative level to see if it's okay to render
        if( FAILED( hr = m_pd3dDevice->TestCooperativeLevel() ) )
        {
            // If the device was lost, do not render until we get it back
            if( D3DERR_DEVICELOST == hr )
                return S_OK;

            // Check if the device needs to be reset.
            if( D3DERR_DEVICENOTRESET == hr )
            {
                // If we are windowed, read the desktop mode and use the same format for
                // the back buffer
                if( m_bWindowed )
                {
                    D3DAdapterInfo* pAdapterInfo = m_d3dSettings.PAdapterInfo();
                    m_pD3D->GetAdapterDisplayMode( pAdapterInfo->AdapterOrdinal, &m_d3dSettings.Windowed_DisplayMode );
                    m_d3dpp.BackBufferFormat = m_d3dSettings.Windowed_DisplayMode.Format;
                }

                if( FAILED( hr = Reset3DEnvironment() ) )
                    return hr;
            }
            return hr;
        }
        m_bDeviceLost = false;
    }

    // Get the app's time, in seconds. Skip rendering if no time elapsed
    FLOAT fAppTime        = DXUtil_Timer( TIMER_GETAPPTIME );
    FLOAT fElapsedAppTime = DXUtil_Timer( TIMER_GETELAPSEDTIME );
    if( ( 0.0f == fElapsedAppTime ) && m_bFrameMoving )
        return S_OK;

    // FrameMove (animate) the scene
    if( m_bFrameMoving || m_bSingleStep )
    {
        // Store the time for the app
        m_fTime        = fAppTime;
        m_fElapsedTime = fElapsedAppTime;

        // Frame move the scene
        if( FAILED( hr = FrameMove() ) )
            return hr;

        m_bSingleStep = false;
    }

    // Render the scene as normal
    if( FAILED( hr = Render() ) )
        return hr;

    UpdateStats();

    // Show the frame on the primary surface.
    hr = m_pd3dDevice->Present( NULL, NULL, NULL, NULL );
    if( D3DERR_DEVICELOST == hr )
        m_bDeviceLost = true;

    return S_OK;
}

第一部分是处理设备丢失的情况，老实说我到底也没弄清楚设备丢失是怎么个情况，貌似切换屏幕会导致设备丢失。不过丢失了就要重新设置有关窗口的设置。调用了下面的重置函数。

HRESULT CD3DApplication::Reset3DEnvironment()
{
    HRESULT hr;

    // Release all vidmem objects
    if( m_bDeviceObjectsRestored )
    {
        m_bDeviceObjectsRestored = false;
        InvalidateDeviceObjects();
    }
    // Reset the device
    if( FAILED( hr = m_pd3dDevice->Reset( &m_d3dpp ) ) )
        return hr;

    // Store render target surface desc
    LPDIRECT3DSURFACE9 pBackBuffer;
    m_pd3dDevice->GetBackBuffer( 0, 0, D3DBACKBUFFER_TYPE_MONO, &pBackBuffer );
    pBackBuffer->GetDesc( &m_d3dsdBackBuffer );
    pBackBuffer->Release();

    // Set up the fullscreen cursor
    if( m_bShowCursorWhenFullscreen && !m_bWindowed )
    {
        HCURSOR hCursor;
#ifdef _WIN64
        hCursor = (HCURSOR)GetClassLongPtr( m_hWnd, GCLP_HCURSOR );
#else
        hCursor = (HCURSOR)ULongToHandle( GetClassLong( m_hWnd, GCL_HCURSOR ) );
#endif
        D3DUtil_SetDeviceCursor( m_pd3dDevice, hCursor, true );
        m_pd3dDevice->ShowCursor( true );
    }

    // Confine cursor to fullscreen window
    if( m_bClipCursorWhenFullscreen )
    {
        if (!m_bWindowed )
        {
            RECT rcWindow;
            GetWindowRect( m_hWnd, &rcWindow );
            ClipCursor( &rcWindow );
        }
        else
        {
            ClipCursor( NULL );
        }
    }

    // Initialize the app's device-dependent objects
    hr = RestoreDeviceObjects();
    if( FAILED(hr) )
    {
        InvalidateDeviceObjects();
        return hr;
    }
    m_bDeviceObjectsRestored = true;

    // If the app is paused, trigger the rendering of the current frame
    if( false == m_bFrameMoving )
    {
        m_bSingleStep = true;
        DXUtil_Timer( TIMER_START );
        DXUtil_Timer( TIMER_STOP );
    }

    return S_OK;
}

这个函数就没有什么好说的了，里面调用的好几个函数都需要子类重写，但基本上功能就是这样了。

Render3DEnvironment剩下的部分就是子类主要工作了，重写渲染场景和更新数据的函数。

那么D3DApp框架的阅读就到此结束。老实说，我觉得D3DApp的条理性比DXUT的要好，为什么要换成以重写回调函数来完成功能的DXUT呢，实在不懂。下一篇，cGameHost类的阅读。