新手问题，怎样才能让DrawPrimitive成功执行?

代码如下：
C/C++ code

#include <d3d9.h>


#pragma comment (lib, "d3d9.lib")



struct s_CustomVertex
{
    float x, y, z, rhw;
    DWORD color;
};


HINSTANCE hInst;
HWND hwndHandle;
LPDIRECT3D9 pD3D;
LPDIRECT3DDEVICE9 pd3dDevice;
LPDIRECT3DVERTEXBUFFER9 g_pVB;



LRESULT CALLBACK WndProc (HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_DESTROY:
        PostQuitMessage (0);
        return 0;
    }
    return DefWindowProc (hWnd, message, wParam, lParam);
}

bool initWindow (HINSTANCE hInstance)
{
    WNDCLASSEX wcex;
    wcex.cbSize = sizeof (WNDCLASSEX);
    wcex.style = CS_HREDRAW | CS_VREDRAW;
    wcex.lpfnWndProc = (WNDPROC) WndProc;
    wcex.cbClsExtra = 0;
    wcex.cbWndExtra = 0;
    wcex.hInstance = hInstance;
    wcex.hIcon = 0;
    wcex.hCursor = LoadCursor (0, IDC_ARROW);
    wcex.hbrBackground = (HBRUSH) (COLOR_WINDOW + 1);
    wcex.lpszMenuName = 0;
    wcex.lpszClassName = "DirectXExample";
    wcex.hIconSm = 0;
    RegisterClassEx (&wcex);

    hwndHandle = CreateWindow (
        "DirectXExample",
        "DirectXExample",
        WS_EX_TOPMOST | WS_POPUP | WS_VISIBLE,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        800,
        600,
        0,
        0,
        hInstance,
        0);
    if (!hwndHandle)
        return false;

    ShowWindow (hwndHandle, SW_SHOW);
    UpdateWindow (hwndHandle);
    return true;
}
HRESULT SetupVB ()
{
    HRESULT hr;

    s_CustomVertex g_Vertices[] = {
        {320, 50, 0.5, 1, D3DCOLOR_ARGB (0,255,0,0)},
        {250, 400, 0.5, 1, D3DCOLOR_ARGB (0,0,255,0)},
        {50, 400, 0.5, 1, D3DCOLOR_ARGB (0,0,0,255)}
    };

    hr = pd3dDevice->CreateVertexBuffer (
        3 * sizeof (s_CustomVertex),
        0,
        D3DFVF_XYZRHW | D3DFVF_DIFFUSE,
        D3DPOOL_DEFAULT,
        &g_pVB,
        0);

    if (FAILED (hr))
        return hr;

    void* pVertices;

    hr = g_pVB->Lock (0, 3 * sizeof (s_CustomVertex), (void**) &pVertices, 0);

    if (FAILED (hr))
        return hr;

    memcpy (pVertices, g_Vertices, 3 * sizeof (s_CustomVertex));

    g_pVB->Unlock ();

    return S_OK;
}
bool initDirect3D ()
{
    // create pD3D object
    pD3D = 0;
    pd3dDevice = 0;

    if (0 == (pD3D = Direct3DCreate9 (D3D_SDK_VERSION)))
        return false;



    // create pd3dDevice object
    D3DPRESENT_PARAMETERS d3dpp;
    ZeroMemory (&d3dpp, sizeof (d3dpp));
    d3dpp.Windowed = TRUE;
    d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
    d3dpp.BackBufferFormat = D3DFMT_X8R8G8B8;
    d3dpp.BackBufferCount = 1;
    d3dpp.BackBufferHeight = 800;
    d3dpp.BackBufferWidth = 600;
    d3dpp.hDeviceWindow = hwndHandle;

    if (FAILED (pD3D->CreateDevice (
        D3DADAPTER_DEFAULT,
        D3DDEVTYPE_REF,
        hwndHandle,
        D3DCREATE_SOFTWARE_VERTEXPROCESSING,
        &d3dpp,
        &pd3dDevice)))
        return false;


    if (FAILED (SetupVB ()))
        return false;


    return true;
}

void render ()
{
    pd3dDevice->Clear (0, 0, D3DCLEAR_TARGET, D3DCOLOR_XRGB (0, 0, 255), 1.0f, 0);

    IDirect3DSurface9* backbuffer = 0;

    pd3dDevice->GetBackBuffer (
        0,
        0,
        D3DBACKBUFFER_TYPE_MONO,
        &backbuffer);


    if (FAILED (pd3dDevice->SetStreamSource (0, g_pVB, 0, sizeof (s_CustomVertex))))
        throw "SetStreamSource";

    if (FAILED (pd3dDevice->SetFVF (D3DFVF_XYZRHW | D3DFVF_DIFFUSE)))
        throw "SetFVF fail";

///////////////////////////////////////////////////////////////////////////////////
    /*下面这条语句不能成功执行*/
    if (FAILED (pd3dDevice->DrawPrimitive (D3DPT_TRIANGLESTRIP, 0, 1)))
        throw "DrawPrimitive fail";
///////////////////////////////////////////////////////////////////////////////////

    pd3dDevice->Present (0, 0, 0, 0);
}

void cleanUp ()
{
    pd3dDevice->Release ();
    pD3D->Release ();
}

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE, LPTSTR lpCmdLine, int nCmdShow)
{
    if (!initWindow (hInstance))
        return 0;

    if (!initDirect3D())
        return 0;

    MSG msg;
    ZeroMemory (&msg, sizeof (msg));
    while (msg.message != WM_QUIT)
    {
        if (PeekMessage (&msg, 0, 0, 0, PM_REMOVE))
        {
            TranslateMessage (&msg);
            DispatchMessage (&msg);
        }
        else
        {
            render ();
        }
    }

    cleanUp ();

    return (int) msg.wParam;
}

求帮助！！

DNF中新手怎么较快的入手呢

缺少IDirect3DDevice9::BeginScene();与IDirect3DDevice9::EndScene()语句
所有绘制必须在这两个语句之间调用。

例：
pd3dDevice->BeginScene();
绘制函数
pd3dDevice->EndScene();
pd3dDevice->Present (0, 0, 0, 0);