c++ - OpenGL 不显示任何内容？

Question

我的问题是我的程序没有在屏幕上显示任何内容。

这是“main.cpp”代码:

#include "paStdAfx.h"
#include "OpenGL.h"

HDC hDC = NULL;
HGLRC hRC = NULL;
HWND hwnd = NULL;
HINSTANCE hInstance = GetModuleHandle(NULL);

const wchar_t* szClassName = _T("*project name :3*");

static std::wstring Titles[] = { 
    _T("*project name :3* - 100% free!"),
    _T("*project name :3* - 100% OpenGL!"),
    _T("*project name :3* - Not cross platform!"),
    _T("*project name :3* - Rawr"),
    _T("*project name :3* - Entirely C++!"),
    _T("*project name :3* - Woo, /r/gamedev!"),
    _T("*project name :3* - Platypi, platypi everywhere."),
    _T("*project name :3* - Nom nom nom"),
    _T("*project name :3* - Thanks, StackExchange!"),
    _T("*project name :3* - DRM Free!"),
    _T("*project name :3* - <3"),
    _T("*project name :3* - Minecraft is also fun!")
};

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
BOOL CreateOpenGLWindow(const wchar_t*, int, int, int);

OpenGL ogl;

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int iCmdShow)
{
    srand(time(NULL));
    const std::wstring wtt = Titles[rand() % 11];
    const wchar_t* WindowTitle = wtt.c_str();

    BOOL done = FALSE;
    MSG msg;

    if(!CreateOpenGLWindow(WindowTitle, 800, 600, 32)){ MessageBox(NULL, _T("Could not create window :("), _T("Error!"), MB_OK | MB_ICONERROR); exit(EXIT_FAILURE); }

    while(!done)
    {
        if(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
        {
            if(msg.message == WM_QUIT)
                done = TRUE;
            else
            {
                TranslateMessage(&msg);
                DispatchMessage(&msg);
            }
        }
        else
        {
            ogl.RenderGLScene();
            SwapBuffers(hDC);
        }
    }

    ogl.KillOpenGL(hwnd, hDC, hRC);
    return 0;
}

BOOL CreateOpenGLWindow(const wchar_t* title, int width, int height, int bits)
{
    WNDCLASSEX wcx = {0};
    DWORD dwExStyle = WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;
    DWORD dwStyle = WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_MINIMIZEBOX;

    wcx.cbSize = sizeof(WNDCLASSEX);
    wcx.style = CS_OWNDC;
    wcx.lpfnWndProc = WndProc;
    wcx.cbClsExtra = 0;
    wcx.cbWndExtra = 0;
    wcx.hInstance = hInstance;
    wcx.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_PROGRAMICON));
    wcx.hCursor = LoadCursor(NULL, IDC_ARROW);
    wcx.hbrBackground = (HBRUSH) (COLOR_WINDOW + 1);
    wcx.lpszClassName = szClassName;
    wcx.lpszMenuName = NULL;
    wcx.hIconSm = (HICON) LoadImage(hInstance, MAKEINTRESOURCE(IDI_PROGRAMICON), IMAGE_ICON, 16, 16, 0);

    if(!RegisterClassEx(&wcx)){ MessageBox(NULL, _T("Failed to register window!"), _T("Error! :("), MB_OK | MB_ICONERROR); exit(EXIT_FAILURE); }
    if(!(hwnd = CreateWindowEx(dwExStyle, szClassName, title, dwStyle, 200, 69, width, height, NULL, NULL, hInstance, NULL))){ MessageBox(NULL, _T("Failed to create the window!"), _T("Error! :("), MB_OK | MB_ICONERROR); exit(EXIT_FAILURE); }

    ogl.CreateOpenGLContext(hwnd, &hDC, &hRC);
    ogl.PrepareOpenGLScene();
    ogl.ResizeGLScene(width, height);

    ShowWindow(hwnd, SW_SHOW);
    SetForegroundWindow(hwnd);
    SetFocus(hwnd);

    return TRUE;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch(msg)
    {
        case WM_CREATE:
            ogl.ProgramIcon(hwnd);
            break;

        case WM_KEYDOWN:
            switch(wParam)
            {
                case VK_ESCAPE:
                    PostQuitMessage(0);
                    break;
            }
            break;

        case WM_CLOSE:
            PostQuitMessage(0);
            break;

        case WM_DESTROY:
            return 0;
    }

    return DefWindowProc(hwnd, msg, wParam, lParam);
}

这是“OpenGL.cpp”代码:

#include "paStdAfx.h"
#include "OpenGL.h"

GLvoid OpenGL::CreateOpenGLContext(HWND hwnd, HDC* hDC, HGLRC* hRC)
{
    PIXELFORMATDESCRIPTOR pfd;
    HGLRC tempContext;

    memset(&pfd, 0, sizeof(PIXELFORMATDESCRIPTOR));
    pfd.nSize = sizeof(PIXELFORMATDESCRIPTOR);
    pfd.nVersion = 1;
    pfd.dwFlags = PFD_DOUBLEBUFFER | PFD_SUPPORT_OPENGL | PFD_DRAW_TO_WINDOW;
    pfd.iPixelType = PFD_TYPE_RGBA;
    pfd.cColorBits = 32;
    pfd.cDepthBits = 32;
    pfd.iLayerType = PFD_MAIN_PLANE;

    *hDC = GetDC(hwnd);

    int PixelFormat = ChoosePixelFormat(*hDC, &pfd);

    if(PixelFormat == 0){ MessageBox(NULL, _T("Could not choose pixel format :("), _T("Error!"), MB_OK | MB_ICONERROR); exit(EXIT_FAILURE); }
    if(!SetPixelFormat(*hDC, PixelFormat, &pfd)){ MessageBox(NULL, _T("Could not set pixel format :("), _T("Error!"), MB_OK | MB_ICONERROR); exit(3); }

    tempContext = wglCreateContext(*hDC);
    wglMakeCurrent(*hDC, tempContext);

    GLenum err = glewInit();
    if(GLEW_OK != err){ MessageBox(NULL, _T("Failed to initialize GLEW! :("), _T("Warning!"), MB_OK | MB_ICONINFORMATION); }

    int attribs[] = {
        WGL_CONTEXT_MAJOR_VERSION_ARB, 3,
        WGL_CONTEXT_MINOR_VERSION_ARB, 1,
        WGL_CONTEXT_FLAGS_ARB,
        WGL_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB,
        0
    };

    if(!glewIsSupported("GL_VERSION_3_1")){ MessageBox(NULL, _T("OpenGL 3.1 not supported :("), _T("Warning!"), MB_OK | MB_ICONERROR); }

    if(wglewIsSupported("WGL_ARB_create_context") == 1)
    {
        *hRC = wglCreateContextAttribsARB(*hDC, 0, attribs);
        wglMakeCurrent(NULL, NULL);
        wglDeleteContext(tempContext);
        wglMakeCurrent(*hDC, *hRC);
    }
    else{ *hRC = tempContext; }

    const char* GLVersionString = (char*) glGetString(GL_VERSION);
    int OpenGLVersion[2];
    glGetIntegerv(GL_MAJOR_VERSION, &OpenGLVersion[0]);
    glGetIntegerv(GL_MINOR_VERSION, &OpenGLVersion[1]);
}

GLvoid OpenGL::PrepareOpenGLScene(GLvoid)
{
    glClearColor(0.0f, 0.6f, 1.0f, 0.0f);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);
}

GLvoid OpenGL::RenderGLScene(GLvoid)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();

    /* Begin OpenGL Rendering */



    /* End OpenGL Rendering */
}

GLvoid OpenGL::ResizeGLScene(int w, int h)
{
    float ratio = 1.0 * w / h;

    if(h == 0)
        h = 1;

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0f, ratio, 0.1f, 1000.0f);
    glViewport(0, 0, w, h);
}

GLvoid OpenGL::ProgramIcon(HWND hwnd)
{
    HICON hIcon, hIconSm;

    hIcon = (HICON) LoadImage(NULL, _T("data/icon.ico"), IMAGE_ICON, 32, 32, LR_LOADFROMFILE);
    if(hIcon)
        SendMessage(hwnd, WM_SETICON, ICON_BIG, (LPARAM)hIcon);
    else
        MessageBox(NULL, _T("Could not load the big icon! :("), _T("Error!"), MB_OK | MB_ICONERROR);

    //---------------------------------------------------------------------------------------------//

    hIconSm = (HICON) LoadImage(NULL, _T("data/icon.ico"), IMAGE_ICON, 16, 16, LR_LOADFROMFILE);
    if(hIconSm)
        SendMessage(hwnd, WM_SETICON, ICON_SMALL, (LPARAM)hIconSm);
    else
        MessageBox(NULL, _T("Could not load the small icon! :("), _T("Error!"), MB_OK | MB_ICONERROR);
}

GLvoid OpenGL::KillOpenGL(HWND hwnd, HDC hDC, HGLRC hRC)
{
    wglMakeCurrent(NULL, NULL);
    wglDeleteContext(hRC);
    ReleaseDC(hwnd, hDC);
}

所有渲染代码都将进入 OpenGL.cpp 中的“RenderGLScene”函数，但是当我放置代码以在屏幕上渲染诸如三角形或正方形之类的基本内容时，什么也没有出现。我也尝试修改“gluLookAt()”函数和“gluPerspective()”函数，因为我认为这些可能是我问题的根源。我已经尝试了 VBO 和使用 glBegin()/glEnd() 的旧方法。

Answer 1

您创建了一个双缓冲上下文，但我没有看到您在完成渲染后执行缓冲区交换 (wglSwapBuffers)。如果没有缓冲区交换，您将看不到任何东西。