天行健 君子當自強而不息

接下來的Create()函數從接口ID3DXFileData創建網格模型：

 

該函數與上一個Create()函數并無太大區別，只是在加載網格模型時調用D3DXLoadMeshFromXof()而不是D3DXLoadMeshFromXW()。

 

最后一個Create()函數從輸入的網格模型中創建新的網格模型：

 

為了優化網格的渲染，函數首先生成網格面鄰接信息緩存：

    DWORD *rgdwAdjacency = NULL;

    rgdwAdjacency = new DWORD[pInMesh->GetNumFaces() * 3];
    if( rgdwAdjacency == NULL )
        return E_OUTOFMEMORY;

    pInMesh->GenerateAdjacency(1e-6f, rgdwAdjacency);

GenerateAdjacency()的聲明如下：

Generate a list of mesh edges, as well as a list of faces that share each edge.

HRESULT GenerateAdjacency(
  FLOAT Epsilon,
  DWORD * pAdjacency
);

Parameters

Epsilon

[in] Specifies that vertices that differ in position by less than epsilon should be treated as coincident.

pAdjacency

[in] Pointer to an array of three DWORDs per face to be filled with the indices of adjacent faces. The number of bytes in this array must be at least 3 * ID3DXBaseMesh::GetNumFaces * sizeof(DWORD).

Return Values

If the method succeeds, the return value is D3D_OK. If the method fails, the return value can be one of the following: D3DERR_INVALIDCALL, E_OUTOFMEMORY.

Remarks

After an application generates adjacency information for a mesh, the mesh data can be optimized for better drawing performance.

The order of the entries in the adjacency buffer is determined by the order of the vertex indices in the index buffer. The adjacent triangle 0 always corresponds to the edge between the indices of the corners 0 and 1. The adjacent triangle 1 always corresponds to the edge between the indices of the corners 1 and 2 while the adjacent triangle 2 corresponds to the edge between the indices of the corners 2 and 0.

為了優化網格的渲染，函數去除了32位索引、系統內存的使用、只寫訪問，增加了托管內存的使用，以及去除了無用的頂點和索引項、根據屬性給三角形排序并調整屬性表，增加了頂點緩存的命中率，并調用Optimize()對網格模型進行優化，優化后的網格模型存儲在pTempMesh中：

    DWORD dwOptions = pInMesh->GetOptions();

    dwOptions &= ~(D3DXMESH_32BIT | D3DXMESH_SYSTEMMEM | D3DXMESH_WRITEONLY);
    dwOptions |= D3DXMESH_MANAGED;
    dwOptions |= D3DXMESHOPT_COMPACT | D3DXMESHOPT_ATTRSORT | D3DXMESHOPT_VERTEXCACHE;

    ID3DXMesh* pTempMesh = NULL;

    if( FAILED( pInMesh->Optimize( dwOptions, rgdwAdjacency, NULL, NULL, NULL, &pTempMesh ) ) )
    {
        SAFE_DELETE_ARRAY( rgdwAdjacency );
        return E_FAIL;
    }

接下來刪除了鄰接數組、網格指針，并將優化后的網格模型指針賦給m_pMesh，并調用CreateMaterials()創建材質和紋理資源：

    SAFE_DELETE_ARRAY( rgdwAdjacency );
    SAFE_RELEASE( m_pMesh );

    m_pMesh = pTempMesh;

    HRESULT hr = CreateMaterials( L"", pd3dDevice, pd3dxMaterials, dwMaterials );

最后從優化后的網格模型中提取數據以方便日后訪問，并調用CreateVertexDeclaration()來創建頂點聲明：

   // Extract data from m_pMesh for easy access

    m_dwNumVertices    = m_pMesh->GetNumVertices();
    m_dwNumFaces       = m_pMesh->GetNumFaces();
    m_dwBytesPerVertex = m_pMesh->GetNumBytesPerVertex();

    m_pMesh->GetIndexBuffer( &m_pIB );
    m_pMesh->GetVertexBuffer( &m_pVB );

    D3DVERTEXELEMENT9 decl[MAX_FVF_DECL_SIZE];
    m_pMesh->GetDeclaration( decl );
    pd3dDevice->CreateVertexDeclaration( decl, &m_pDecl );

    return hr;

CreateVertexDeclaration()的聲明如下：

Create a vertex shader declaration from the device and the vertex elements.

HRESULT CreateVertexDeclaration(
  CONST D3DVERTEXELEMENT9* pVertexElements,
  IDirect3DVertexDeclaration9** ppDecl
);

Parameters

pVertexElements

[in] An array of D3DVERTEXELEMENT9 vertex elements.

ppDecl

[out, retval] Pointer to an IDirect3DVertexDeclaration9 pointer that returns the created vertex shader declaration.

Return Values

If the method succeeds, the return value is D3D_OK. If the method fails, the return value can be D3DERR_INVALIDCALL.

Remarks

See the Vertex Declaration (Direct3D 9) page for a detailed description of how to map vertex declarations between different versions of DirectX.

 

函數Destroy()用來在程序退出時銷毀指定的資源：

HRESULT CDXUTMesh::Destroy()
{
    InvalidateDeviceObjects();

    for( UINT i=0; i<m_dwNumMaterials; i++ )
        SAFE_RELEASE( m_pTextures[i] );

    SAFE_DELETE_ARRAY( m_pTextures );
    SAFE_DELETE_ARRAY( m_pMaterials );
    SAFE_DELETE_ARRAY( m_strMaterials );

    SAFE_RELEASE( m_pMesh );

    m_dwNumMaterials = 0L;

    return S_OK;
}