OpenGL不會畫我的四邊形

Question

我已經使用Java學習了一些OpenGL。 現在，我正在嘗試過渡到C ++。 我正在嘗試設置一個窗口並渲染一個四邊形，但未顯示出來。 我只是黑屏。 我以OpenGL Superbible為例。

這是我的代碼：

#include <stdio.h>

#define GLEW_STATIC
#include "include\GL\glew.h"
#include "include\GL\wglew.h"

#pragma comment(lib, "lib\\glew32s.lib")
#pragma comment(lib, "opengl32.lib")
#pragma comment(lib, "glu32.lib")

HWND         g_hWnd;
HGLRC        g_hRC;
HDC          g_hDC;
HINSTANCE    g_hInstance;
WNDCLASS     g_windClass; 
RECT         g_windowRect;
bool         g_ContinueRendering;

void RenderScene(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glColor4f(1.0f, 1.0f, 1.0f, 1.0f);

    glBegin(GL_QUADS);
    glVertex3f(-10.0f, -10.0f, 5.0f);
    glVertex3f(-10.0f, 10.0f, 5.0f);
    glVertex3f(10.0f, 10.0f, 5.0f);
    glVertex3f(10.0f, -10.0f, 5.0f);
    glEnd();
    printf("%s", gluErrorString(glGetError()));
    SwapBuffers(g_hDC);
}

///////////////////////////////////////////////////////////////////////////////
// Window has changed size, or has just been created. In either case, we need
// to use the window dimensions to set the viewport and the projection matrix.
void ChangeSize(int w, int h)
{
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(90.0f, float(w) / float(h), 1.0f, 500.0f);
}

///////////////////////////////////////////////////////////////////////////////
// Callback functions to handle all window functions this app cares about.
// Once complete, pass message on to next app in the hook chain.
LRESULT CALLBACK WndProc(   HWND    hWnd,       // Handle For This Window
                            UINT    uMsg,       // Message For This Window
                            WPARAM  wParam,     // Additional Message Information
                            LPARAM  lParam)     // Additional Message Information
{
    unsigned int key = 0;

    // Handle relevant messages individually
    switch(uMsg)
    {
    case WM_ACTIVATE:
    case WM_SETFOCUS:
        RenderScene();
        return 0;
    case WM_SIZE:
        ChangeSize(LOWORD(lParam),HIWORD(lParam));
        RenderScene();
        break;
    case WM_CLOSE:
        g_ContinueRendering = false;
        PostQuitMessage(0);
        return 0;
    default:
        // Nothing to do now
        break;
    }

    // Pass All Unhandled Messages To DefWindowProc
    return DefWindowProc(hWnd,uMsg,wParam,lParam);
}

bool setupWindow(int nWidth, int nHeight)
{
    bool bRetVal = true;

    int nWindowX = 0;
    int nWindowY = 0;
    int nPixelFormat  = -1;
    PIXELFORMATDESCRIPTOR pfd;

    DWORD dwExtStyle;
    DWORD dwWindStyle;

    HINSTANCE g_hInstance = GetModuleHandle(NULL);

    TCHAR szWindowName[50] =  TEXT("Block Redux");
    TCHAR szClassName[50]  =  TEXT("OGL_CLASS");

    // setup window class
    g_windClass.lpszClassName = szClassName;                // Set the name of the Class
    g_windClass.lpfnWndProc   = (WNDPROC)WndProc;
    g_windClass.hInstance     = g_hInstance;                // Use this module for the module handle
    g_windClass.hCursor       = LoadCursor(NULL, IDC_ARROW);// Pick the default mouse cursor
    g_windClass.hIcon         = LoadIcon(NULL, IDI_WINLOGO);// Pick the default windows icons
    g_windClass.hbrBackground = NULL;                       // No Background
    g_windClass.lpszMenuName  = NULL;                       // No menu for this window
    g_windClass.style         = CS_HREDRAW | CS_OWNDC |     // set styles for this class, specifically to catch
                                CS_VREDRAW;                 // window redraws, unique DC, and resize
    g_windClass.cbClsExtra    = 0;                          // Extra class memory
    g_windClass.cbWndExtra    = 0;                          // Extra window memory

    // Register the newly defined class
    if(!RegisterClass( &g_windClass ))
        bRetVal = false;

    dwExtStyle  = WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;
    dwWindStyle = WS_OVERLAPPEDWINDOW;
    ShowCursor(TRUE);

    g_windowRect.left   = nWindowX;
    g_windowRect.right  = nWindowX + nWidth;
    g_windowRect.top    = nWindowY;
    g_windowRect.bottom = nWindowY + nHeight;

    // Setup window width and height
    AdjustWindowRectEx(&g_windowRect, dwWindStyle, FALSE, dwExtStyle);

    //Adjust for adornments
    int nWindowWidth = g_windowRect.right   - g_windowRect.left;
    int nWindowHeight = g_windowRect.bottom - g_windowRect.top;

    // Create window
    g_hWnd = CreateWindowEx(dwExtStyle,     // Extended style
                            szClassName,    // class name
                            szWindowName,   // window name
                            dwWindStyle |        
                            WS_CLIPSIBLINGS | 
                            WS_CLIPCHILDREN,// window stlye
                            nWindowX,       // window position, x
                            nWindowY,       // window position, y
                            nWindowWidth,   // height
                            nWindowHeight,  // width
                            NULL,           // Parent window
                            NULL,           // menu
                            g_hInstance,    // instance
                            NULL);          // pass this to WM_CREATE

    // now that we have a window, setup the pixel format descriptor
    g_hDC = GetDC(g_hWnd);

    // Set a dummy pixel format so that we can get access to wgl functions
    SetPixelFormat( g_hDC, 1,&pfd);
    // Create OGL context and make it current
    g_hRC = wglCreateContext( g_hDC );
    wglMakeCurrent( g_hDC, g_hRC );

    if (g_hDC == 0 ||
        g_hDC == 0)
    {
        bRetVal = false;
        printf("!!! An error occured creating an OpenGL window.\n");
    }

    // Setup GLEW which loads OGL function pointers
    GLenum err = glewInit();
    if (GLEW_OK != err)
    {
        /* Problem: glewInit failed, something is seriously wrong. */
        bRetVal = false;
        printf("Error: %s\n", glewGetErrorString(err));
    }
    const GLubyte *oglVersion = glGetString(GL_VERSION);
    printf("This system supports OpenGL Version %s.\n", oglVersion);

    // Now that extensions are setup, delete window and start over picking a real format.
    wglMakeCurrent(NULL, NULL);
    wglDeleteContext(g_hRC);
    ReleaseDC(g_hWnd, g_hDC);
    DestroyWindow(g_hWnd);

    // Create the window again
    g_hWnd = CreateWindowEx(dwExtStyle,     // Extended style
                            szClassName,    // class name
                            szWindowName,   // window name
                            dwWindStyle |        
                            WS_CLIPSIBLINGS | 
                            WS_CLIPCHILDREN,// window stlye
                            nWindowX,       // window position, x
                            nWindowY,       // window position, y
                            nWindowWidth,   // height
                            nWindowHeight,  // width
                            NULL,           // Parent window
                            NULL,           // menu
                            g_hInstance,    // instance
                            NULL);          // pass this to WM_CREATE

    g_hDC = GetDC(g_hWnd);

    int nPixCount = 0;

    // Specify the important attributes we care about
    int pixAttribs[] =
    {
        WGL_SUPPORT_OPENGL_ARB, 1, // Must support OGL rendering
        WGL_DRAW_TO_WINDOW_ARB, 1, // pf that can run a window
        WGL_COLOR_BITS_ARB,     24, // 8 bits of each R, G and B
        WGL_DEPTH_BITS_ARB,     16, // 16 bits of depth precision for window
        WGL_DOUBLE_BUFFER_ARB,  GL_TRUE, // Double buffered context
        WGL_SAMPLE_BUFFERS_ARB, GL_TRUE, // MSAA on
        WGL_SAMPLES_ARB,        8, // 8x MSAA
        WGL_PIXEL_TYPE_ARB,     WGL_TYPE_RGBA_ARB, // pf should be RGBA type
        0 // NULL termination
    }; 

    // Ask OpenGL to find the most relevant format matching our attribs
    // Only get one format back.
    wglChoosePixelFormatARB(g_hDC, &pixAttribs[0], NULL, 1, &nPixelFormat, (UINT*)&nPixCount);

    if(nPixelFormat == -1) 
    {
        // Couldn't find a format, perhaps no 3D HW or drivers are installed
        g_hDC = 0;
        g_hDC = 0;
        bRetVal = false;
        printf("!!! An error occurred trying to find a pixel format with the requested attribs.\n");
    }
    else
    {
        // Got a format, now set it as the current one
        SetPixelFormat( g_hDC, nPixelFormat, &pfd );

        GLint attribs[] = {WGL_CONTEXT_MAJOR_VERSION_ARB,  3,
                           WGL_CONTEXT_MINOR_VERSION_ARB,  3,
                           0 };

        g_hRC = wglCreateContextAttribsARB(g_hDC, 0, attribs);
        if (g_hRC == NULL)
        {
            printf("!!! Could not create an OpenGL 3.3 context.\n");
            attribs[3] = 2;
            g_hRC = wglCreateContextAttribsARB(g_hDC, 0, attribs);
            if (g_hRC == NULL)
            {
                printf("!!! Could not create an OpenGL 3.2 context.\n");
                attribs[3] = 1;
                g_hRC = wglCreateContextAttribsARB(g_hDC, 0, attribs);
                if (g_hRC == NULL)
                {
                    printf("!!! Could not create an OpenGL 3.1 context.\n");
                    attribs[3] = 0;
                    g_hRC = wglCreateContextAttribsARB(g_hDC, 0, attribs);
                    if (g_hRC == NULL)
                    {
                        printf("!!! Could not create an OpenGL 3.0 context.\n");
                        printf("!!! OpenGL 3.0 and higher are not supported on this system.\n");
                    }
                }
            }
        }

        wglMakeCurrent( g_hDC, g_hRC );
    }

    if (g_hDC == 0 ||
        g_hDC == 0)
    {
        bRetVal = false;
        printf("!!! An error occured creating an OpenGL window.\n");
    }

    // If everything went as planned, display the window 
    if( bRetVal )
    {
        ShowWindow( g_hWnd, SW_SHOW );
        SetForegroundWindow( g_hWnd );
        SetFocus( g_hWnd );
        g_ContinueRendering = true;
    }

    return bRetVal;
}

///////////////////////////////////////////////////////////////////////////////
// Cleanup window, OGL context and related state
// Called on exit and on error
bool KillWindow( )
{ 
    bool bRetVal = true;

    //Cleanup OGL RC
    if(g_hRC) 
    {
        wglMakeCurrent(NULL, NULL);
        wglDeleteContext(g_hRC);
        g_hRC = NULL;
    }

    // release the DC
    if(g_hDC)
    {
        ReleaseDC(g_hWnd, g_hDC);
        g_hDC = NULL;
    }

    // Destroy the window
    if(g_hWnd)
    {
        DestroyWindow(g_hWnd);
        g_hWnd = NULL;;
    }

    // Delete the window class
    TCHAR szClassName[50]  =  TEXT("OGL_CLASS");
    UnregisterClass(szClassName, g_hInstance);
    g_hInstance = NULL;
    ShowCursor(TRUE);
    return bRetVal;
}

///////////////////////////////////////////////////////////////////////////////
// Main rendering loop
// Check for window messages and handle events, also draw scene
void mainLoop()
{
    MSG msg;

    // Check for waiting mssgs
    if (PeekMessage(&msg,NULL,0,0,PM_REMOVE))
    {
        if (msg.message==WM_QUIT)
        {
            g_ContinueRendering = false;
        }
        else
        {
            // Deal with mssgs
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }
    else
    {
        RenderScene();       

    }
}

int main(int argc, char **argv)
{
    if(setupWindow(800, 600))
    {
        ChangeSize(800, 600);

        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        glEnable(GL_BLEND);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();

        while (g_ContinueRendering)
        {   
            mainLoop();
        }
    }
    KillWindow();
    return 0;
}

我很確定所有窗口設置程序都可以正常工作。 如果我更改glClearColor，則窗口顏色會更改。

我希望有人可以看到問題所在。

Answer 1

查看您的代碼，您正在使用OpenGL3.x。

嘗試使用三角形，因為不推薦使用GL_QUADS 。

另外，您應將CreateContextAttrib傳遞給您所需的最低版本，如果可用，您將自動獲得更新的版本。

Answer 2

您正在吸引他們。 四邊形的z值為+5，但是在OpenGL中，z方向的正向為負。 將z值更改為-5，我想您會看到的。

或添加：

glPushMatrix();
glTranslatef(0,0,-20.0f);
//Your code for drawing.
glBegin(GL_QUADS);
...
glEnd();
//Added
glPopMatrix();

Answer 3

我只是從臀部射擊，但是您是否嘗試過更改頂點的順序？ 這可能是背面剔除的元凶。