D3D的初始化

要開始D3D編程，首先是要初始化D3D環境，SDK文檔的tutorial將整個過程分爲幾部

1. 建立一個窗體
2. 初始化D3D
   • 獲取IDirect3D9的指針
   • 檢查設備的性能、對API的支持能力
   • 初始化D3DPRESENT_PARAMETERS
   • 使用D3DPRESENT_PARAMETER的參數建立IDirectDDevice9
3. 處理消息
4. 渲染&顯示場景
5. 關閉D3D，退出程序

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1. 建立窗體
   以前說過，D3D程序是在一個windows窗體的客戶區進行繪製，D3D至關於畫筆的話，這個窗體就是畫布，因此在初始化D3D以前首先要有一個窗體，根據簡單的Windows API編程回顧的內容，建立一個簡單窗體並不難。
   • 定義窗口類

   WNDCLASS wclass;

   • 註冊窗口類

   RegisterClass(&wclass);

   • 建立窗口

   CreateWindow(...);

2. 初始化D3D
   一旦建立好了窗體，就能夠在這個基礎上進一步去初始化D3D，建立D3D設備，以在窗體這個畫布上進行繪圖，初始化D3D的過程能夠分爲四部。
   • 獲取IDirect3D9的指針，遊戲開發中最經常使用的就是COM配合DirectX技術，這兒IDirect3D9就是一個表示D3D9的COM接口，所以不能直接使用C++的new操做符

   LPDIRECT3D9 g_pD3D9;    //IDirect3D9 *g_pD3D9；
   g_pD3D9 = Direct3DCreate9（D3D_SDK_VERSION);

   • 檢查設備性能，對API的支持程度(如硬件TnL,這個是比較老的固定功能流水線中所採用的一些東西，現代的可編程流水線已經見不着了)

   //以硬件TnL爲例
   D3DCAPS9 d3dcap;
   int hwTnL = 0;
   g_pD3D9->GetDeviceCaps(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, &d3dcaps);
   if(caps.Devcaps & D3DDEVCAPS_HWTRANSFORMANDLIGHT)
       hwTnL = D3DCREATE_HARDWARE_VERTEXPROCESSING;
   else
       hwTnL = D3DCREATE_SOFTWARE_VERTEXPROCESSING;

   • 創建一個D3DPRESENT_PARAMETERS

   D3DPRESENT_PARAMETERS d3dpp;
   //按需設置d3dpp的各種屬性

   • 創建D3D設備

   g_pD3D9->CreateDevice(D3DADAPTER,
                         D3DDEVTYPE,
                         HWND, BEHAVIOR_FLAGS
                         D3DPRESENT_PARAMETERS*,
                         IDirect3DDevice9 **);

   至此，D3D的初始化就完成了

3. 處理消息
   就如簡單的Windows API編程回顧中所述，遊戲程序多數不是事件驅動的，於是能夠使用PeekMessage處理消息

   MSG msg;
   while(PeekMessage(&msg, 0, 0, 0, 0))
   {
       if(msg.message == WM_QUIT)
           break;
       TranslateMessage(&msg);
       DispatchMessage(&msg);
   }
   //Game Codes

4. 渲染&顯示場景
   • 清除後臺緩存,將後臺緩存置爲所設定的顏色，將深度或模板緩存設置爲須要的值

   //IDirect3DDevice9::Clear
   g_pD3DDEV9->Clear(DWORD Count, const D3DRECT *pRects,
                     DWORD flags, D3DCOLOR Color, float Z, DWORD Stencil);

   • 向後臺緩存繪製場景

   g_pD3DDEV9->BeginScene();
   //Render Codes
   g_pD3DDEV9->EndScene();

   • 提交下一幀後臺緩存，僅僅是提交，尚未顯示

   //IDirect3DDevice9::Present
   g_pD3DDEV9->Present(0,0,0,0）;

5. 關閉D3D，退出程序
   退出程序不困難，但以前要先關閉D3D。以前說了g_pD3D9和g_pD3DDEV9是兩個COM接口指針，而COM不能夠使用C++的new/delete操做符來建立和銷燬，因此須要手動的來釋放一下

g_pD3D9->Release();
g_pD3D9 = NULL;
g_pD3DDEV9->Release();
g_pD3DDEV9 = NULL;

至此，整個D3D程序流程就結束了

所有代碼以下

#include <windows.h>
#include <d3d9.h>
#include <strsafe.h>

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


LPDIRECT3D9         g_pD3D9;
LPDIRECT3DDEVICE9   g_pD3D9dev;

HWND hMain;

bool initWinApp(HINSTANCE hInstance, int iCmdShow);
LRESULT CALLBACK MsgProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

HRESULT D3DInit(HWND hWnd);
void D3DRender();
void D3DCleanup();


int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR cmd, int iCmdShow)
{
    if( !initWinApp(hInstance, iCmdShow) )
    {
        ::MessageBox(0, TEXT("initWinApp Failed!"), TEXT("ERROR"), MB_OK);
        return 0;
    }

    if( SUCCEEDED(D3DInit(hMain)) )
    {
        ::ShowWindow(hMain, iCmdShow);
        ::UpdateWindow(hMain);

        MSG msg;
        while( PeekMessage(&msg, 0, 0, 0, 0 ) )
        {
            if( msg.message == WM_QUIT )
                break;
            msg.message = WM_PAINT;
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }

    D3DCleanup();
    UnregisterClass(L"D3DInit", hInstance);
    return 0;


}

bool initWinApp(HINSTANCE hInstance, int iCmdshow)
{
    WNDCLASS wc;
    wc.style        = CS_HREDRAW | CS_VREDRAW; 
    wc.lpfnWndProc  = MsgProc;
    wc.cbClsExtra   = 0;
    wc.cbWndExtra   = 0;
    wc.hInstance    = hInstance;
    wc.hIcon        = ::LoadIcon(0, IDI_APPLICATION);
    wc.hCursor      = ::LoadCursor(0, IDC_ARROW);
    wc.hbrBackground= static_cast<HBRUSH>(::GetStockObject(WHITE_BRUSH));
    wc.lpszMenuName = 0;
    wc.lpszClassName= TEXT("D3DInit");

    if( !RegisterClass(&wc) )
    {
        ::MessageBox(0, TEXT("RegisterClass Failed!"), TEXT("ERROR"), MB_OK);
        return false;
    }

    if( (hMain = CreateWindow(TEXT("D3DInit"), TEXT("D3DInit"), WS_OVERLAPPEDWINDOW, CW_USEDEFAULT,
        CW_USEDEFAULT, 800, 600, NULL, NULL, hInstance, NULL)) == NULL)
    {
        ::MessageBox(0, TEXT("CreateWindow Failed!"), TEXT("ERROR"), MB_OK);
        return false;
    }

    return true;
}

HRESULT D3DInit(HWND hWnd)
{
    //acquire pointer to IDirect3D9
    if( (g_pD3D9 = Direct3DCreate9(D3D_SDK_VERSION)) == NULL )
    {
        ::MessageBox(0, TEXT("Direct3DCreate Failed!"), TEXT("ERROR"), MB_OK);
        return E_FAIL;
    }

    //Check Device Capabilities, here we check the hardware TnL support
    D3DCAPS9 caps;
    g_pD3D9->GetDeviceCaps(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, &caps);
    int hardwareTnL = 0;
    if( caps.DevCaps & D3DDEVCAPS_HWTRANSFORMANDLIGHT )
        hardwareTnL = D3DCREATE_HARDWARE_VERTEXPROCESSING;
    else
        hardwareTnL = D3DCREATE_SOFTWARE_VERTEXPROCESSING;

    //setup D3DPRESENT_PARAMETERS which defines the behavior of the D3D app 
    D3DPRESENT_PARAMETERS d3dpp;
    d3dpp.BackBufferWidth           = 800;
    d3dpp.BackBufferHeight          = 600;
    d3dpp.BackBufferCount           = 2;
    d3dpp.BackBufferFormat          = D3DFMT_A8R8G8B8;
    d3dpp.MultiSampleType           = D3DMULTISAMPLE_NONE;
    d3dpp.MultiSampleQuality        = 0;
    d3dpp.SwapEffect                = D3DSWAPEFFECT_DISCARD;
    d3dpp.hDeviceWindow             = hMain;
    d3dpp.Windowed                  = 1;
    d3dpp.EnableAutoDepthStencil    = TRUE;
    d3dpp.AutoDepthStencilFormat    = D3DFMT_D24S8;
    d3dpp.Flags                     = 0;
    d3dpp.FullScreen_RefreshRateInHz= D3DPRESENT_RATE_DEFAULT;
    d3dpp.PresentationInterval      = D3DPRESENT_INTERVAL_IMMEDIATE;

    //Create D3D device
    if( FAILED(g_pD3D9->CreateDevice(D3DADAPTER_DEFAULT,
                                    D3DDEVTYPE_HAL,
                                    hWnd,
                                    hardwareTnL,
                                    &d3dpp,
                                    &g_pD3D9dev)) )
    {
        MessageBox(0, TEXT("CreateDevice Failed"), TEXT("ERROR"), MB_OK);
        return E_FAIL;
    }

    return S_OK;
}

LRESULT CALLBACK MsgProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch( msg )
    {
    case WM_DESTROY:
        ::PostQuitMessage(0);
        return 0;
    case WM_PAINT:
        D3DRender();
        ValidateRect(hWnd, NULL);
        return 0;
    }
    return DefWindowProc(hWnd, msg, wParam, lParam);
}

void D3DRender()
{
    //Set BackBuffer
    g_pD3D9dev->Clear(0, NULL, D3DCLEAR_TARGET,D3DCOLOR_XRGB( 0, 255, 0 ), 1.0f, 0 );

    //Render in this section
    if( SUCCEEDED(g_pD3D9dev->BeginScene()) )
    {
        g_pD3D9dev->EndScene();
    }

    //Present BackBuffer
    g_pD3D9dev->Present(NULL, NULL, NULL, NULL);
}

void D3DCleanup()
{
    if( g_pD3D9dev != NULL )
    {
        g_pD3D9dev->Release();
    }
    if( g_pD3D9 != NULL )
    {
        g_pD3D9->Release();
    }
}