天行健 君子當自強而不息

類CDXUTMeshFile位于DXUTMesh.h和DXUTMesh.cpp中，繼承自類CDXUTMeshFrame，其實類CDXUTMeshFrame本身只完成一些基礎操作，不是最終使用的一個類，CDXUTMeshFile在CDXUTMeshFrame的基礎上將各種操作進一步封裝。

在.x網格模型中使用框架的主要目的是實現模型自身包含的動畫，而CDXUTMeshFile和CDXUTMeshFrame雖然考慮了網格模型的層次框架，可是并沒有實現對網格模型動畫的播放，所以通常不直接使用這兩個類，因為對于不包含動畫信息的靜態網格模型CDXUTMesh類就已經足夠了。當然也完全可以像使用CDXUTMesh類一樣使用CDXUTMeshFile類來操作不包含動畫信息的網格模型。

來看看CDXUTMeshFile的定義：

LoadMesh()負責從ID3DXFileData中加載一個網格，該函數是內部調用的，其實質是調用CDXUTMesh::Create()函數來加載。

 

LoadFrame()用于從ID3DXFileData中加載一個框架：

首先，該函數調用GetType()獲取對象的GUID：

    // Get the type of the object
    if( FAILED( hr = pFileData->GetType( &Guid ) ) )
        return hr;

接下來根據GUID分別進行相應的操作，若是網格則調用LoadMesh()加載網格，若是框架變換矩陣則設置變換矩陣，若是框架，相應的操作有些復雜，首先獲取框架的名稱并將其轉化為widechar類型：

       if( FAILED( hr = pFileData->GetName(strAnsiName, &dwNameLength) ) )
            return hr;

        MultiByteToWideChar(CP_ACP, 0, strAnsiName, -1, strName, 512);
        strName[511] = 0;

接著新建一個CDXUTMeshFrame對象并將其添加進鏈表：

        // Create the frame
        pCurrentFrame = new CDXUTMeshFrame(strName);
        if(pCurrentFrame == NULL)
            return E_OUTOFMEMORY;

        pCurrentFrame->m_pNext = pParentFrame->m_pChild;
        pParentFrame->m_pChild = pCurrentFrame;

最后遍歷子框架并遞歸調用LoadFrame()加載框架:

        // Enumerate child objects

        pFileData->GetChildren(&cChildren);

        for (UINT iChild = 0; iChild < cChildren; iChild++)
        {
            // Query the child for its FileData
            hr = pFileData->GetChild(iChild, &pChildData);

            if( SUCCEEDED(hr) )
            {
                hr = LoadFrame(pd3dDevice, pChildData, pCurrentFrame);
                SAFE_RELEASE( pChildData );
            }

            if( FAILED(hr) )
                return hr;
        }

 

第一個Create()函數負責從模型文件加載網格模型：

首先函數創建了一個ID3DXFileData對象并注冊了XFILE標準模板：

    // Create a x file object
    if( FAILED( hr = D3DXFileCreate(&pDXFile) ) )
        return E_FAIL;

    // Register templates for d3drm and patch extensions.
    if( FAILED( hr = pDXFile->RegisterTemplates((void*) D3DRM_XTEMPLATES, D3DRM_XTEMPLATE_BYTES) ) )
    {
        SAFE_RELEASE( pDXFile );
        return E_FAIL;
    }

接下來查找網格模型文件將路徑存儲在strPath中，并將該路徑轉化為ANSI類型存儲在strPathANSI中：

    // Find the path to the file, and convert it to ANSI (for the D3DXOF API)

    WCHAR strPath[MAX_PATH];
    CHAR  strPathANSI[MAX_PATH];
    DXUTFindDXSDKMediaFileCch(strPath, sizeof(strPath) / sizeof(WCHAR), strFilename);        

    WideCharToMultiByte(CP_ACP, 0, strPath, -1, strPathANSI, MAX_PATH, NULL, NULL);
    strPathANSI[MAX_PATH - 1] = 0;

再接下來創建一個ID3DXFileEnumObject枚舉對象負責從.x文件中讀取數據：

    // Create enum object
    hr = pDXFile->CreateEnumObject((void*) strPathANSI, D3DXF_FILELOAD_FROMFILE, &pEnumObj);

    if( FAILED(hr) )
    {
        SAFE_RELEASE( pDXFile );
        return hr;
    }

函數CreateEnumObject()聲明如下：

Creates an enumerator object that will read a .x file.

HRESULT CreateEnumObject(
  LPCVOID pvSource,
  D3DXF_FILELOADOPTIONS loadflags,
  ID3DXFileEnumObject ** ppEnumObj
);

Parameters

pvSource

[out] The data source. Either:

• A file name
• A D3DXF_FILELOADMEMORY structure
• A D3DXF_FILELOADRESOURCE structure

Depending on the value of loadflags.

loadflags

[in] Value that specifies the source of the data. This value can be one of the D3DXF_FILELOADOPTIONS flags.

ppEnumObj

[out] Address of a pointer to an ID3DXFileEnumObject interface, representing the created enumerator object.

Return Values

If the method succeeds, the return value is S_OK. If the method fails, the return value can be one of the following: D3DXFERR_BADVALUE, D3DXFERR_PARSEERROR.

Remarks

After using this method, use one of the ID3DXFileEnumObject methods to retrieve a data object.

再接下來通過ID3DXFileEnumObjec枚舉對象讀取數據并調用LoadFrame()加載框架：

    // Enumerate top level objects (which are always frames)
    pEnumObj->GetChildren(&cChildren);

    for (UINT iChild = 0; iChild < cChildren; iChild++)
    {
        hr = pEnumObj->GetChild(iChild, &pFileData);
        if (FAILED(hr))
            return hr;

        hr = LoadFrame(pd3dDevice, pFileData, this);
        SAFE_RELEASE(pFileData);

        if( FAILED(hr) )
        {
            SAFE_RELEASE(pEnumObj);
            SAFE_RELEASE(pDXFile);
            return E_FAIL;
        }
    }

最后釋放不再使用的COM對象：

    SAFE_RELEASE(pFileData);
    SAFE_RELEASE(pEnumObj);
    SAFE_RELEASE(pDXFile);

 

第二個Create()函數與第一個非常類似，只是該函數負責從資源加載網格模型：

唯一需要解釋的代碼是：

    D3DXF_FILELOADRESOURCE dxlr;

    dxlr.hModule = NULL;
    dxlr.lpName = strResourceAnsi;
    dxlr.lpType = strTypeAnsi;

    // Create enum object
    hr = pDXFile->CreateEnumObject((void*) &dxlr, D3DXF_FILELOAD_FROMRESOURCE, &pEnumObj);

該代碼片段負責從指定的資源中加載網格模型，D3DXF_FILELOADRESOURCE的聲明如下:

Identifies resource data.

typedef struct D3DXF_FILELOADRESOURCE {
    HMODULE hModule;
    LPCSTR lpName;
    LPCSTR lpType;
} D3DXF_FILELOADRESOURCE, *LPD3DXF_FILELOADRESOURCE;

Members

hModule

Handle of the module containing the resource to be loaded. If this member is NULL, the resource must be attached to the executable file that will use it.

lpName

Pointer to a string specifying the name of the resource to be loaded. For example, if the resource is a mesh, this member should specify the name of the mesh file.

lpType

Pointer to a string specifying the user-defined type identifying the resource.

Remarks

This structure identifies a resource to be loaded when an application uses the ID3DXFile::CreateEnumObject method and specifies the D3DXF_FILELOAD_FROMRESOURCE flag.

 

Render()函數負責網格模型的渲染，它允許用戶在調用時設置一個世界坐標矩陣：

因為CDXUTMeshFile繼承自CDXUTMeshFrame，并且該類的默認構造函數定義如下：

CDXUTMeshFile() : CDXUTMeshFrame( L"CDXUTMeshFile_Root" ) {}

也就是說在創建該類對象時默認創建了一個CDXUTMeshFrame對象，這也意味著在加載網格模型時所有后續的CDXUTMeshFrame對象都是該對象的子對象，所以下面的代碼是合法的:

    // Render opaque subsets in the meshes
    if(m_pChild)
        m_pChild->Render(pd3dDevice, TRUE, FALSE, &matWorld);

    // Enable alpha blending
    pd3dDevice->SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE);
    pd3dDevice->SetRenderState(D3DRS_SRCBLEND,  D3DBLEND_SRCALPHA);
    pd3dDevice->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);

    // Render alpha subsets in the meshes
    if(m_pChild)
        m_pChild->Render(pd3dDevice, FALSE, TRUE, &matWorld);

    // Restore state
    pd3dDevice->SetRenderState(D3DRS_ALPHABLENDENABLE, FALSE);
    pd3dDevice->SetTransform(D3DTS_WORLD, &matSavedWorld);

先渲染所有不透明的子框架對象，再渲染所有半透明的子框架對象，最后恢復到先前的渲染狀態。