《精通DirectX 3D》 第三十一章 三维场景交互 01_Pick

《精通DirectX 3D》 第三十一章 三维场景交互 01_Pick

// =============================================================================
//  Desc: 主程序源代码
// =============================================================================
#include  " dxstdafx.h "
#include  " resource.h "
#define  MAX_INTERSECTIONS 16


// -----------------------------------------------------------------------------
//  全局变量
// -----------------------------------------------------------------------------
ID3DXFont *                  g_pFont  =  NULL;           // ID3DXFont字体对象
ID3DXSprite *                g_pTextSprite  =  NULL;     // ID3DXSprite文本精灵对象
bool                        g_bShowHelp  =   true ;       // 标识是否显示简单说明文本

CDXUTDialogResourceManager g_DialogResourceManager;  // 对话框资源管理器
CD3DSettingsDlg            g_SettingsDlg;            // Direct3D设备设置对话框
CDXUTDialog                g_HUD;                    // 对话框
CDXUTDialog                g_SampleUI;               // 对话框

CDXUTMesh                  g_pMesh;                    // 网格模型对象
LPD3DXMESH                 g_pPickMesh;                // 用于计算拾取三角形的网格对象
DWORD                      g_dwNumIntersections  =   0 ;   // 拾取到的面的数量
LPDIRECT3DVERTEXBUFFER9    g_pVB  =  NULL;               // 存放所拾取到的三角形的顶点缓冲区
DWORD                      g_IntersectionArray[MAX_INTERSECTIONS];  // 存储拾取到三角形的索引


// -----------------------------------------------------------------------------
//  Desc: 顶点结构
// -----------------------------------------------------------------------------
struct  D3DVERTEX
{
    D3DXVECTOR3 p;
    D3DXVECTOR3 n;
     float        tu, tv;

     static   const  DWORD FVF;
};
const  DWORD D3DVERTEX::FVF  =  D3DFVF_XYZ  |  D3DFVF_NORMAL  |  D3DFVF_TEX1;


// -----------------------------------------------------------------------------
//  控件ID
// -----------------------------------------------------------------------------
#define  IDC_TOGGLEFULLSCREEN      1
#define  IDC_TOGGLEREF             2
#define  IDC_CHANGEDEVICE          3


// -----------------------------------------------------------------------------
//  Desc: 函数声明
// ------------------------------------------------------------------------------
bool     CALLBACK IsDeviceAcceptable( D3DCAPS9 *  pCaps, D3DFORMAT AdapterFormat, D3DFORMAT BackBufferFormat,  bool  bWindowed,  void *  pUserContext );
bool     CALLBACK ModifyDeviceSettings( DXUTDeviceSettings *  pDeviceSettings,  const  D3DCAPS9 *  pCaps,  void *  pUserContext );
HRESULT CALLBACK OnCreateDevice( IDirect3DDevice9 *  pd3dDevice,  const  D3DSURFACE_DESC *  pBackBufferSurfaceDesc,  void *  pUserContext );
HRESULT CALLBACK OnResetDevice( IDirect3DDevice9 *  pd3dDevice,  const  D3DSURFACE_DESC *  pBackBufferSurfaceDesc,  void *  pUserContext );
void     CALLBACK OnFrameMove( IDirect3DDevice9 *  pd3dDevice,  double  fTime,  float  fElapsedTime,  void *  pUserContext );
void     CALLBACK OnFrameRender( IDirect3DDevice9 *  pd3dDevice,  double  fTime,  float  fElapsedTime,  void *  pUserContext );
LRESULT CALLBACK MsgProc( HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam,  bool *  pbNoFurtherProcessing,  void *  pUserContext );
void     CALLBACK KeyboardProc( UINT nChar,  bool  bKeyDown,  bool  bAltDown,  void *  pUserContext );
void     CALLBACK OnGUIEvent( UINT nEvent,  int  nControlID, CDXUTControl *  pControl,  void *  pUserContext );
void     CALLBACK OnLostDevice(  void *  pUserContext );
void     CALLBACK OnDestroyDevice(  void *  pUserContext );

void     InitApp();
void     RenderText();
HRESULT Pick_Triangle(IDirect3DDevice9 *  pd3dDevice, LPD3DXMESH pMesh);


// -----------------------------------------------------------------------------
//  Desc: 入口函数
// -----------------------------------------------------------------------------
INT WINAPI WinMain( HINSTANCE, HINSTANCE, LPSTR,  int  )
{
     // 为Debug配置启用运行时内存检查功能
#if  defined(DEBUG) | defined(_DEBUG)
    _CrtSetDbgFlag( _CRTDBG_ALLOC_MEM_DF  |  _CRTDBG_LEAK_CHECK_DF );
#endif

     // 设置回调函数
    DXUTSetCallbackDeviceCreated( OnCreateDevice );
    DXUTSetCallbackDeviceReset( OnResetDevice );
    DXUTSetCallbackDeviceLost( OnLostDevice );
    DXUTSetCallbackDeviceDestroyed( OnDestroyDevice );
    DXUTSetCallbackMsgProc( MsgProc );
    DXUTSetCallbackKeyboard( KeyboardProc );
    DXUTSetCallbackFrameRender( OnFrameRender );
    DXUTSetCallbackFrameMove( OnFrameMove );

     // 应用程序相关的初始化
    InitApp();

     // 初始化DXUT, 创建窗口, 创建Direct3D设备对象
    DXUTInit(  true ,  true ,  true  );
    DXUTSetCursorSettings(  true ,  true  );
    DXUTCreateWindow( L " Pick "  );
    DXUTCreateDevice( D3DADAPTER_DEFAULT,  true ,  640 ,  480 , 
        IsDeviceAcceptable, ModifyDeviceSettings );

     // 进入消息循环和场景渲染
    DXUTMainLoop();

     // 在此进行应用程序相关的清除工作

     return  DXUTGetExitCode();
}


// -----------------------------------------------------------------------------
//  Desc: 应用程序相关初始化
// -----------------------------------------------------------------------------
void  InitApp()
{
     // 初始化对话框
    g_SettingsDlg.Init(  & g_DialogResourceManager );
    g_HUD.Init(  & g_DialogResourceManager );
    g_SampleUI.Init(  & g_DialogResourceManager );

     // 为g_HUD对话框设置消息处理函数,添加控件
    g_HUD.SetCallback( OnGUIEvent );  int  iY  =   10 ; 
    g_HUD.AddButton( IDC_TOGGLEFULLSCREEN, L " Toggle full screen " ,  35 , iY,  125 ,  22  );
    g_HUD.AddButton( IDC_TOGGLEREF, L " Toggle REF (F3) " ,  35 , iY  +=   24 ,  125 ,  22  );
    g_HUD.AddButton( IDC_CHANGEDEVICE, L " Change device (F2) " ,  35 , iY  +=   24 ,  125 ,  22 , VK_F2 );
}


// -----------------------------------------------------------------------------
//  Desc: 设备能力检查
// -----------------------------------------------------------------------------
bool  CALLBACK IsDeviceAcceptable( D3DCAPS9 *  pCaps, D3DFORMAT AdapterFormat, 
                                  D3DFORMAT BackBufferFormat,  bool  bWindowed, 
                                   void *  pUserContext )
{
     // 检查后台缓冲区格式是否支持Alpha混合等操作(post pixel blending operations)
    IDirect3D9 *  pD3D  =  DXUTGetD3DObject(); 
     if ( FAILED( pD3D -> CheckDeviceFormat( pCaps -> AdapterOrdinal, pCaps -> DeviceType,
                    AdapterFormat, D3DUSAGE_QUERY_POSTPIXELSHADER_BLENDING, 
                    D3DRTYPE_TEXTURE, BackBufferFormat ) ) )
         return   false ;

     return   true ;
}


// -----------------------------------------------------------------------------
//  Desc: 修改Direct3D渲染设备设置
// -----------------------------------------------------------------------------
bool  CALLBACK ModifyDeviceSettings( DXUTDeviceSettings *  pDeviceSettings, 
                                     const  D3DCAPS9 *  pCaps,  void *  pUserContext )
{
     // 如果不支持硬件顶点处理则使用软件顶点处理
     if ( (pCaps -> DevCaps  &  D3DDEVCAPS_HWTRANSFORMANDLIGHT)  ==   0 )
    {
        pDeviceSettings -> BehaviorFlags  =  D3DCREATE_SOFTWARE_VERTEXPROCESSING;
    }

     // 如果使用参考设备,则弹出警告对话框
     static   bool  s_bFirstTime  =   true ;
     if ( s_bFirstTime )
    {
        s_bFirstTime  =   false ;
         if ( pDeviceSettings -> DeviceType  ==  D3DDEVTYPE_REF )
            DXUTDisplaySwitchingToREFWarning();
    }

     return   true ;
}


// -----------------------------------------------------------------------------
//  Desc: 在此创建管理内存资源对象
// -----------------------------------------------------------------------------
HRESULT CALLBACK OnCreateDevice( IDirect3DDevice9 *  pd3dDevice, 
                                 const  D3DSURFACE_DESC *  pBackBufferSurfaceDesc, 
                                 void *  pUserContext )
{
    HRESULT hr;

    V_RETURN( g_DialogResourceManager.OnCreateDevice( pd3dDevice ) );
    V_RETURN( g_SettingsDlg.OnCreateDevice( pd3dDevice ) );
    
     // 创建字体
    V_RETURN( D3DXCreateFont( pd3dDevice,  15 ,  0 , FW_BOLD,  1 , FALSE, DEFAULT_CHARSET, 
                         OUT_DEFAULT_PRECIS, DEFAULT_QUALITY, DEFAULT_PITCH  |  FF_DONTCARE, 
                         L " Arial " ,  & g_pFont ) );

     // 创建老虎网格模型
    V_RETURN(g_pMesh.Create(pd3dDevice, L " Media\\tiger.x " ));
    V_RETURN(g_pMesh.SetFVF(pd3dDevice, D3DVERTEX::FVF));

    g_pMesh.GetMesh() -> CloneMeshFVF(D3DXMESH_MANAGED, g_pMesh.GetMesh() -> GetFVF(), pd3dDevice,  & g_pPickMesh);

     // 创建存放所拾取到的三角形的顶点缓冲区
    DWORD dwNumVertices  =  MAX_INTERSECTIONS  *   3 ;
    V_RETURN( pd3dDevice -> CreateVertexBuffer( dwNumVertices * sizeof (D3DVERTEX),
                                              D3DUSAGE_WRITEONLY, D3DVERTEX::FVF,
                                              D3DPOOL_MANAGED,  & g_pVB, NULL ) );

     return  hr;
}


// -----------------------------------------------------------------------------
//  Desc: 在此创建默认内存类型资源对象, 设置相关渲染状态
// -----------------------------------------------------------------------------
HRESULT CALLBACK OnResetDevice( IDirect3DDevice9 *  pd3dDevice, 
                                 const  D3DSURFACE_DESC *  pBackBufferSurfaceDesc, 
                                 void *  pUserContext )
{
    HRESULT hr;

    V_RETURN( g_DialogResourceManager.OnResetDevice() );
    V_RETURN( g_SettingsDlg.OnResetDevice() );

     // 设置对话框位置和尺寸
    g_HUD.SetLocation( pBackBufferSurfaceDesc -> Width - 170 ,  0  );
    g_HUD.SetSize(  170 ,  170  );
    g_SampleUI.SetLocation( pBackBufferSurfaceDesc -> Width - 170 , 
                            pBackBufferSurfaceDesc -> Height - 350  );
    g_SampleUI.SetSize(  170 ,  300  );

     // 恢复字体
     if ( g_pFont )
        V_RETURN( g_pFont -> OnResetDevice() );
   
     // 创建ID3DXSprite接口对象
    V_RETURN( D3DXCreateSprite( pd3dDevice,  & g_pTextSprite ) );

     // 设置观察矩阵
    D3DXMATRIXA16 matView;
    D3DXVECTOR3 vEyePt(  0.0f ,  2.0f , - 4.0f  );
    D3DXVECTOR3 vLookatPt(  0.0f ,  0.0f ,  0.0f  );
    D3DXVECTOR3 vUpVec(  0.0f ,  1.0f ,  0.0f  );
    D3DXMatrixLookAtLH(  & matView,  & vEyePt,  & vLookatPt,  & vUpVec );
    pd3dDevice -> SetTransform( D3DTS_VIEW,  & matView );

     // 设置投影矩阵
    D3DXMATRIXA16 matProj;
     float  fAspectRatio  =  ( float )pBackBufferSurfaceDesc -> Width  /  pBackBufferSurfaceDesc -> Height;
    D3DXMatrixPerspectiveFovLH(  & matProj, D3DX_PI / 4 , fAspectRatio,  1.0f ,  1000.0f  );
    pd3dDevice -> SetTransform( D3DTS_PROJECTION,  & matProj );

     // 设置纹理渲染状态
    pd3dDevice -> SetTextureStageState(  0 , D3DTSS_COLORARG1, D3DTA_TEXTURE );
    pd3dDevice -> SetTextureStageState(  0 , D3DTSS_COLOROP,   D3DTOP_SELECTARG1 );
    pd3dDevice -> SetSamplerState(  0 , D3DSAMP_MINFILTER, D3DTEXF_LINEAR );
    pd3dDevice -> SetSamplerState(  0 , D3DSAMP_MAGFILTER, D3DTEXF_LINEAR );

     // 关闭光照
    pd3dDevice -> SetRenderState( D3DRS_LIGHTING,  false  );

     return  S_OK;
}


// -----------------------------------------------------------------------------
//  Desc: 更新场景
// -----------------------------------------------------------------------------
void  CALLBACK OnFrameMove( IDirect3DDevice9 *  pd3dDevice,  double  fTime, 
                            float  fElapsedTime,  void *  pUserContext )
{
     // 世界变换
    D3DXMATRIXA16 matWorld;
    UINT  iTime   =  timeGetTime()  %   10000 ;
    FLOAT fAngle  =  iTime  *  ( 2.0f   *  D3DX_PI)  /   10000.0f ;
    D3DXMatrixRotationY(  & matWorld, fAngle );
    pd3dDevice -> SetTransform( D3DTS_WORLD,   & matWorld );

     // 拾取三角形
    Pick_Triangle(pd3dDevice, g_pPickMesh);    
}


// -----------------------------------------------------------------------------
//  Desc: 渲染场景
// -----------------------------------------------------------------------------
void  CALLBACK OnFrameRender( IDirect3DDevice9 *  pd3dDevice,  double  fTime, 
                             float  fElapsedTime,  void *  pUserContext )
{
    HRESULT hr;
  
     // 如果正在利用Direct3D设备设置对话框进行设置, 则不渲染场景
     if ( g_SettingsDlg.IsActive() )
    {
        g_SettingsDlg.OnRender( fElapsedTime );
         return ;
    }

     // 清除后台颜色缓冲区和深度缓冲区
    V( pd3dDevice -> Clear( 0 , NULL, D3DCLEAR_TARGET  |  D3DCLEAR_ZBUFFER, 
                         D3DCOLOR_ARGB( 0 ,  45 ,  50 ,  170 ),  1.0f ,  0 ) );

     // 开始渲染场景
     if ( SUCCEEDED( pd3dDevice -> BeginScene() ) )
    {        
         if ( g_dwNumIntersections  >   0  )  // 有三角形被拾取到
        {
             // 绘制被拾取到的三角形
            pd3dDevice -> SetFVF( D3DVERTEX::FVF );
            pd3dDevice -> SetStreamSource(  0 , g_pVB,  0 ,  sizeof (D3DVERTEX) );
            pd3dDevice -> SetRenderState( D3DRS_FILLMODE, D3DFILL_SOLID );
            pd3dDevice -> DrawPrimitive( D3DPT_TRIANGLELIST,  0 , g_dwNumIntersections );

             // 使用线填充模式
            pd3dDevice -> SetRenderState( D3DRS_FILLMODE, D3DFILL_WIREFRAME );
        }
         else
        {
             // 使用面填充模式
            pd3dDevice -> SetRenderState( D3DRS_FILLMODE, D3DFILL_SOLID );
        }

         // 渲染网格模型
        g_pMesh.Render( pd3dDevice );

         // 渲染文本和对话框
        DXUT_BeginPerfEvent( DXUT_PERFEVENTCOLOR, L " HUD / Stats "  ); 
        RenderText();
        V( g_HUD.OnRender( fElapsedTime ) );
        V( g_SampleUI.OnRender( fElapsedTime ) );
        DXUT_EndPerfEvent();

         // 结束渲染场景
        V( pd3dDevice -> EndScene() );
    }
}


// -----------------------------------------------------------------------------
//  Desc: 渲染文本
// -----------------------------------------------------------------------------
void  RenderText()
{
    CDXUTTextHelper txtHelper( g_pFont, g_pTextSprite,  15  );

     // 显示当前Direct3D设备状态和渲染帧速率
    txtHelper.Begin();
    txtHelper.SetInsertionPos(  5 ,  5  );
    txtHelper.SetForegroundColor( D3DXCOLOR(  1.0f ,  1.0f ,  0.0f ,  1.0f  ) );
    txtHelper.DrawTextLine( DXUTGetFrameStats( true ) );
    txtHelper.DrawTextLine( DXUTGetDeviceStats() );

     // 显示其他简要信息
    txtHelper.SetForegroundColor( D3DXCOLOR(  1.0f ,  1.0f ,  1.0f ,  1.0f  ) );
    txtHelper.DrawTextLine( L " 三角形拾取演示 "  );
    
     // 显示简单帮助文本
     const  D3DSURFACE_DESC *  pd3dsdBackBuffer  =  DXUTGetBackBufferSurfaceDesc();
     if ( g_bShowHelp )
    {
        txtHelper.SetInsertionPos(  10 , pd3dsdBackBuffer -> Height - 15 * 6  );
        txtHelper.SetForegroundColor( D3DXCOLOR(  1.0f ,  0.75f ,  0.0f ,  1.0f  ) );
        txtHelper.DrawTextLine( L " Controls (F1 to hide): "  );

        txtHelper.SetInsertionPos(  40 , pd3dsdBackBuffer -> Height - 15 * 5  );
        txtHelper.DrawTextLine( L " Quit: ESC "  );
    }
     else
    {
        txtHelper.SetInsertionPos(  10 , pd3dsdBackBuffer -> Height - 15 * 2  );
        txtHelper.SetForegroundColor( D3DXCOLOR(  1.0f ,  1.0f ,  1.0f ,  1.0f  ) );
        txtHelper.DrawTextLine( L " Press F1 for help "  );
    }
    txtHelper.End();
}


// -----------------------------------------------------------------------------
//  Desc: 消息处理
// -----------------------------------------------------------------------------
LRESULT CALLBACK MsgProc( HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam, 
                          bool *  pbNoFurtherProcessing,  void *  pUserContext )
{
      * pbNoFurtherProcessing  =  g_DialogResourceManager.MsgProc( hWnd, uMsg, wParam, lParam );
     if (  * pbNoFurtherProcessing )
         return   0 ;

     if ( g_SettingsDlg.IsActive() )
    {
        g_SettingsDlg.MsgProc( hWnd, uMsg, wParam, lParam );
         return   0 ;
    }

     * pbNoFurtherProcessing  =  g_HUD.MsgProc( hWnd, uMsg, wParam, lParam );
     if (  * pbNoFurtherProcessing )
         return   0 ;
   
     * pbNoFurtherProcessing  =  g_SampleUI.MsgProc( hWnd, uMsg, wParam, lParam );
     if (  * pbNoFurtherProcessing )
         return   0 ;

     // 消息循环
     switch ( uMsg )
    {
     case  WM_LBUTTONDOWN:
        SetCapture( hWnd );    // 捕获
         break ;

     case  WM_LBUTTONUP:
        ReleaseCapture();     // 释放
         break ;
    }

     return   0 ;
}

// -----------------------------------------------------------------------------
//  Desc: 键盘消息处理
// -----------------------------------------------------------------------------
void  CALLBACK KeyboardProc( UINT nChar,  bool  bKeyDown,  bool  bAltDown,  void *  pUserContext )
{
     if ( bKeyDown )
    {
         switch ( nChar )
        {
             case  VK_F1: g_bShowHelp  =   ! g_bShowHelp;  break ;
        }
    }
}


// -----------------------------------------------------------------------------
//  Desc: 处理各种控件消息
// -----------------------------------------------------------------------------
void  CALLBACK OnGUIEvent( UINT nEvent,  int  nControlID, CDXUTControl *  pControl, 
                          void *  pUserContext )
{
     switch ( nControlID )
    {
         case  IDC_TOGGLEFULLSCREEN:
            DXUTToggleFullScreen(); 
             break ;

         case  IDC_TOGGLEREF:
            DXUTToggleREF(); 
             break ;

         case  IDC_CHANGEDEVICE:
            g_SettingsDlg.SetActive(  ! g_SettingsDlg.IsActive() ); 
             break ;
    }
}


// -----------------------------------------------------------------------------
//  Desc: 释放在OnResetDevice()中创建的资源
// -----------------------------------------------------------------------------
void  CALLBACK OnLostDevice(  void *  pUserContext )
{
    g_DialogResourceManager.OnLostDevice();
    g_SettingsDlg.OnLostDevice();
     if ( g_pFont )
        g_pFont -> OnLostDevice();
    SAFE_RELEASE( g_pTextSprite );
}


// ------------------------------------------------------------------------------
//  Desc: 释放在OnCreateDevice()中创建的资源
// ------------------------------------------------------------------------------
void  CALLBACK OnDestroyDevice(  void *  pUserContext )
{
    g_DialogResourceManager.OnDestroyDevice();
    g_SettingsDlg.OnDestroyDevice();
    SAFE_RELEASE( g_pFont );

    g_pMesh.Destroy();
    SAFE_RELEASE(g_pPickMesh);
    SAFE_RELEASE(g_pVB);
}


// -----------------------------------------------------------------------------
//  Desc: 拾取三角形
// -----------------------------------------------------------------------------
HRESULT Pick_Triangle(IDirect3DDevice9 *  pd3dDevice, LPD3DXMESH pMesh)
{
    HRESULT hr  =  S_OK;
    g_dwNumIntersections  =   0L ;

     if (  ! GetCapture() )
         return  hr;

     // 计算拾取射线相关变量声明
    POINT        ptCursor;   // 鼠标位置
    D3DXMATRIX   matWorld, matView, pmatProj, m;
    D3DXVECTOR3  vPickRayOrig, vPickRayDir;
     int           iWidth, iHeight;

     // 获取后台缓冲区的宽度和高度
    iWidth  =  DXUTGetBackBufferSurfaceDesc() -> Width;
    iHeight  =  DXUTGetBackBufferSurfaceDesc() -> Height;

     // 获取当前鼠标在窗口客户区中的位置
    GetCursorPos(  & ptCursor );
    ScreenToClient( DXUTGetHWND(),  & ptCursor );
    
     // 获取当前设备的变换矩阵
    pd3dDevice -> GetTransform( D3DTS_WORLD,  & matWorld );
    pd3dDevice -> GetTransform( D3DTS_VIEW,  & matView );
    pd3dDevice -> GetTransform( D3DTS_PROJECTION,  & pmatProj );

     // 计算世界观察矩阵的逆矩阵
    D3DXMATRIX mWorldView  =  matWorld  *  matView;
    D3DXMatrixInverse(  & m, NULL,  & mWorldView );
    
     // 计算拾取射线的方向与原点
    D3DXVECTOR3 vTemp;
    vTemp.x  =   (((  2.0f   *  ptCursor.x )  /  iWidth  )  -   1  )  /  pmatProj._11;
    vTemp.y  =   - (((  2.0f   *  ptCursor.y )  /  iHeight )  -   1  )  /  pmatProj._22;
    vTemp.z  =    1.0f ;

    vPickRayDir.x   =  vTemp.x * m._11  +  vTemp.y * m._21  +  vTemp.z * m._31;
    vPickRayDir.y   =  vTemp.x * m._12  +  vTemp.y * m._22  +  vTemp.z * m._32;
    vPickRayDir.z   =  vTemp.x * m._13  +  vTemp.y * m._23  +  vTemp.z * m._33;

    vPickRayOrig.x  =  m._41;
    vPickRayOrig.y  =  m._42;
    vPickRayOrig.z  =  m._43;

     // 计算被拾取到的三角形, 得到拾取到三角形的索引
    BOOL               bHit;
    LPD3DXBUFFER       pBuffer  =  NULL;
    D3DXINTERSECTINFO *  pIntersectInfoArray;
    
    V_RETURN( D3DXIntersect( pMesh,  & vPickRayOrig,  & vPickRayDir,  & bHit, 
                             NULL, NULL, NULL, NULL, 
                             & pBuffer,  & g_dwNumIntersections ));

     if ( g_dwNumIntersections  >   0  )
    {
        pIntersectInfoArray  =  (D3DXINTERSECTINFO * )pBuffer -> GetBufferPointer();
         if ( g_dwNumIntersections  >  MAX_INTERSECTIONS )
            g_dwNumIntersections  =  MAX_INTERSECTIONS;
         for ( DWORD iIntersection  =   0 ; iIntersection  <  g_dwNumIntersections; iIntersection ++  )
        {
            g_IntersectionArray[iIntersection]  =  pIntersectInfoArray[iIntersection].FaceIndex;
        }
    }
    SAFE_RELEASE( pBuffer );

     // 根据拾取到三角形的索引, 将三角形顶点数据添加到g_pVB中
    LPDIRECT3DVERTEXBUFFER9  pVB;
    LPDIRECT3DINDEXBUFFER9   pIB;
    WORD *                     pIndices;
    D3DVERTEX *                pVertices;

    pMesh -> GetVertexBuffer(  & pVB );
    pMesh -> GetIndexBuffer(  & pIB );
    pIB -> Lock(  0 ,  0 , ( void ** ) & pIndices,  0  );
    pVB -> Lock(  0 ,  0 , ( void ** ) & pVertices,  0  );

     if ( g_dwNumIntersections  >   0  )
    {
        D3DVERTEX *  v;
        D3DVERTEX *  vThisTri;
        WORD *       iThisTri;
        DWORD *      pIntersection;

        g_pVB -> Lock(  0 ,  0 , ( void ** ) & v,  0  );

         for ( DWORD iIntersection  =   0 ; iIntersection  <  g_dwNumIntersections; iIntersection ++  )
        {
            pIntersection  =   & g_IntersectionArray[iIntersection];
            vThisTri       =   & v[iIntersection  *   3 ];
            iThisTri       =   & pIndices[ 3 * ( * pIntersection)];  

            vThisTri[ 0 ]  =  pVertices[iThisTri[ 0 ]];
            vThisTri[ 1 ]  =  pVertices[iThisTri[ 1 ]];
            vThisTri[ 2 ]  =  pVertices[iThisTri[ 2 ]];
        }

        g_pVB -> Unlock();
    }

    pVB -> Unlock();
    pIB -> Unlock();
    SAFE_RELEASE(pVB);
    SAFE_RELEASE(pIB);
    
     return  S_OK;
}