i got error when assining a pointer to a member RRS feed

  • Question

  • i have converted  the native C++ transparency project (from DirectX10 SDk 2010) to vb.NET, and the vb sample works fine but there is a point concerning assining a value (an IntPtr) to a member of a structure: a piece of code is:

    ' g_QuadVertices is an array of structure:

    Dim g_QuadVertices(0 To 5) As QuadVertex
            g_QuadVertices(0).v3Pos = New D3DXVECTOR3(-1.0F, -1.0F, 0.0F)
            g_QuadVertices(0).v3Normal = New D3DXVECTOR3(0.0F, 0.0F, -1.0F)
            g_QuadVertices(0).v2TexCoord = New D3DXVECTOR2(0.0F, 1.0F)
            g_QuadVertices(1).v3Pos = New D3DXVECTOR3(-1.0F, 1.0F, 0.0F)
            g_QuadVertices(1).v3Normal = New D3DXVECTOR3(0.0F, 0.0F, -1.0F)
            g_QuadVertices(1).v2TexCoord = New D3DXVECTOR2(0.0F, 0.0F)
            g_QuadVertices(2).v3Pos = New D3DXVECTOR3(1.0F, -1.0F, 0.0F)
            g_QuadVertices(2).v3Normal = New D3DXVECTOR3(0.0F, 0.0F, -1.0F)
            g_QuadVertices(2).v2TexCoord = New D3DXVECTOR2(1.0F, 1.0F)
            g_QuadVertices(3).v3Pos = New D3DXVECTOR3(-1.0F, 1.0F, 0.0F)
            g_QuadVertices(3).v3Normal = New D3DXVECTOR3(0.0F, 0.0F, -1.0F)
            g_QuadVertices(3).v2TexCoord = New D3DXVECTOR2(0.0F, 0.0F)
            g_QuadVertices(4).v3Pos = New D3DXVECTOR3(1.0F, 1.0F, 0.0F)
            g_QuadVertices(4).v3Normal = New D3DXVECTOR3(0.0F, 0.0F, -1.0F)
            g_QuadVertices(4).v2TexCoord = New D3DXVECTOR2(1.0F, 0.0F)
            g_QuadVertices(5).v3Pos = New D3DXVECTOR3(1.0F, -1.0F, 0.0F)
            g_QuadVertices(5).v3Normal = New D3DXVECTOR3(0.0F, 0.0F, -1.0F)
            g_QuadVertices(5).v2TexCoord = New D3DXVECTOR2(1.0F, 1.0F)

    Dim _all As IntPtr = Marshal.AllocHGlobal(Marshal.SizeOf(GetType(QuadVertex)) * g_QuadVertices.Length) 
            Dim g_QuadVertices_p(0 To g_QuadVertices.Length) As IntPtr
            For i = 0 To g_QuadVertices.Length - 1
                g_QuadVertices_p(i) = Marshal.AllocHGlobal(Marshal.SizeOf(GetType(QuadVertex)))
                Marshal.StructureToPtr(g_QuadVertices(i), g_QuadVertices_p(i), True)
            Next i

            Marshal.Copy(g_QuadVertices_p, 0, _all, g_QuadVertices_p.Length)
            InitData.pSysMem = _all

    so the sample does not show the quad (nothing is shown) but if the code above is replaced with the following code , it works

    BOOL ver2(QuadVertex sv[],  D3D10_SUBRESOURCE_DATA * InitData)

    InitData->pSysMem = (void*)sv;

    return TRUE;

    remark: the ver2 function is the bridge between the vb.NET project and the native C++ code:

    so finally , what is the equivalent vb.NET code for the line : InitData->pSysMem = (void*)sv;

    Wednesday, April 3, 2019 2:18 PM

All replies

  • may be the error is related to the member pSysMem of the object InitData, idon't know
    Wednesday, April 3, 2019 2:23 PM
  • If all of the values are structures, then try this:

       Dim h = GCHandle.Alloc(g_QuadVertices, GCHandleType.Pinned)

       Dim _all = h.AddrOfPinnedObject()


       InitData.pSysMem = _all


       ' . . .



    Wednesday, April 3, 2019 5:41 PM
  • yes , you are correct
    Wednesday, April 3, 2019 8:02 PM
  • Hi,

    Is your problem solved? If so, please mark the useful replies as answers.  

    Best Regards,


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    Thursday, April 4, 2019 2:42 AM