c - 三角形不显示在 OpenGL 应用程序中

Question

我正在尝试制作我的第一个多边形。

因为我写了一个代码，编译了它，瞧......三角形没有显示:(

这段代码有什么问题？

#pragma once

#include <Windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <gl\GL.h>
#include <gl\glu.h>
#include <gl\glut.h>

HDC         hDC=NULL;
HGLRC       hRC=NULL;

GLvoid GL_ReSizeGLScene(GLsizei width, GLsizei height);
int GL_init( GLvoid );
int GL_drawit( GLvoid );

typedef struct {
    HWND hWnd;
} Glab_t;

static Glab_t glab;

char szClassName[ ] = "GLab";

static LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {
    switch (message) {
        case WM_DESTROY:
            PostQuitMessage (0);
            break;
        case WM_SIZE:
            GL_ReSizeGLScene(LOWORD(lParam),HIWORD(lParam));
            break;
        default:
            return DefWindowProc (hwnd, message, wParam, lParam);
    }
    return 0;
}


int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
    MSG messages;
    RECT rect;
    WNDCLASSEX wndClass;
    int screenWidth, screenHeight;
    int x, y, w, h;
    GLuint      PixelFormat;

    screenWidth = GetSystemMetrics(SM_CXSCREEN);
    screenHeight = GetSystemMetrics(SM_CYSCREEN);

    rect.left = (screenWidth - 582) / 2;
    rect.top = (screenHeight - 358) / 2;
    rect.right = rect.left + 582;
    rect.bottom = rect.top + 358;

    x = rect.left;
    y = rect.top;
    w = 640;
    h = 480;


    wndClass.hInstance = hInstance;
    wndClass.lpszClassName = szClassName;
    wndClass.lpfnWndProc = WindowProcedure;
    wndClass.style = CS_DBLCLKS;
    wndClass.cbSize = sizeof (WNDCLASSEX);
    wndClass.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wndClass.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    wndClass.hCursor = LoadCursor (NULL, IDC_ARROW);
    wndClass.lpszMenuName = NULL;
    wndClass.cbClsExtra = 0;
    wndClass.cbWndExtra = 0;
    wndClass.hbrBackground = (HBRUSH)(COLOR_BTNFACE + 1);

    if (!RegisterClassEx (&wndClass)) {
        return 0;
    }

    glab.hWnd = CreateWindowEx (
           0,
           szClassName,
           "GLab - OpenGL",
           WS_OVERLAPPEDWINDOW,
           x,
           y,
           w,
           h,
           HWND_DESKTOP,
           NULL,
           hInstance,
           NULL 
           );

    static  PIXELFORMATDESCRIPTOR pfd=  {
        sizeof(PIXELFORMATDESCRIPTOR),
        1,
        PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,
        PFD_TYPE_RGBA,
        16, // Can be 32 tough :)
        0, 0, 0, 0, 0, 0,
        0,
        0,
        0,
        0, 0, 0, 0, 
        16, 
        0,
        0,
        PFD_MAIN_PLANE, 
        0,
        0, 0, 0 
    };

    if (!(hDC=GetDC(glab.hWnd))) {
        MessageBox(NULL,"Can't Create A GL Device Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if (!(PixelFormat=ChoosePixelFormat(hDC,&pfd))) {
        MessageBox(NULL,"Can't Find A Suitable PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if(!SetPixelFormat(hDC,PixelFormat,&pfd)) {
        MessageBox(NULL,"Can't Set The PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if (!(hRC=wglCreateContext(hDC))) {
        MessageBox(NULL,"Can't Create A GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if(!wglMakeCurrent(hDC,hRC)) {
        MessageBox(NULL,"Can't Activate The GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    ShowWindow (glab.hWnd, nCmdShow);
    SetForegroundWindow(glab.hWnd);
    SetFocus(glab.hWnd);
    GL_ReSizeGLScene( w, h );

    if (!GL_init() ) {
        MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return false;
    }

    if( !GL_drawit() ) {
        MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return false;
    }

    while (GetMessage (&messages, NULL, 0, 0)) {
        TranslateMessage(&messages);
        DispatchMessage(&messages);
    }

    return messages.wParam;
}

GLvoid GL_ReSizeGLScene(GLsizei width, GLsizei height) {
    if (height==0) {
        height=1;
    }

    glViewport(0,0,width,height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

int GL_init( GLvoid ) {
    glShadeModel(GL_SMOOTH);
    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);
    glClearDepth(1.0f);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
    return true;
}

int GL_drawit( GLvoid ) {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glTranslatef(-1.5f,0.0f,-6.0f);
    glBegin(GL_TRIANGLES);
        glVertex3f( 0.0f, 1.0f, 0.0f);
        glVertex3f(-1.0f,-1.0f, 0.0f);
        glVertex3f( 1.0f,-1.0f, 0.0f);
    glEnd();            
    return true;
}

使用 MC Visual C++ 2010 Express 和 OpenGL 1.4。

Answer 1

你需要一个 SwapBuffers()渲染场景后调用:

#include <Windows.h>
#include <GL/GL.h>
#include <GL/GLU.h>

HDC         hDC=NULL;
HGLRC       hRC=NULL;

GLvoid GL_ReSizeGLScene(GLsizei width, GLsizei height);
int GL_init( GLvoid );
int GL_drawit( GLvoid );

typedef struct {
    HWND hWnd;
} Glab_t;

static Glab_t glab;

char szClassName[ ] = "GLab";

static LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {
    switch (message) {
        case WM_DESTROY:
            PostQuitMessage (0);
            break;
        case WM_SIZE:
            GL_ReSizeGLScene(LOWORD(lParam),HIWORD(lParam));
            break;
        default:
            return DefWindowProc (hwnd, message, wParam, lParam);
    }
    return 0;
}


int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
    MSG messages;
    RECT rect;
    WNDCLASSEX wndClass;
    int screenWidth, screenHeight;
    int x, y, w, h;
    GLuint      PixelFormat;

    screenWidth = GetSystemMetrics(SM_CXSCREEN);
    screenHeight = GetSystemMetrics(SM_CYSCREEN);

    rect.left = (screenWidth - 582) / 2;
    rect.top = (screenHeight - 358) / 2;
    rect.right = rect.left + 582;
    rect.bottom = rect.top + 358;

    x = rect.left;
    y = rect.top;
    w = 640;
    h = 480;


    wndClass.hInstance = hInstance;
    wndClass.lpszClassName = szClassName;
    wndClass.lpfnWndProc = WindowProcedure;
    wndClass.style = CS_DBLCLKS;
    wndClass.cbSize = sizeof (WNDCLASSEX);
    wndClass.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wndClass.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    wndClass.hCursor = LoadCursor (NULL, IDC_ARROW);
    wndClass.lpszMenuName = NULL;
    wndClass.cbClsExtra = 0;
    wndClass.cbWndExtra = 0;
    wndClass.hbrBackground = (HBRUSH)(COLOR_BTNFACE + 1);

    if (!RegisterClassEx (&wndClass)) {
        return 0;
    }

    glab.hWnd = CreateWindowEx (
           0,
           szClassName,
           "GLab - OpenGL",
           WS_OVERLAPPEDWINDOW,
           x,
           y,
           w,
           h,
           HWND_DESKTOP,
           NULL,
           hInstance,
           NULL 
           );

    static  PIXELFORMATDESCRIPTOR pfd=  {
        sizeof(PIXELFORMATDESCRIPTOR),
        1,
        PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,
        PFD_TYPE_RGBA,
        16, // Can be 32 tough :)
        0, 0, 0, 0, 0, 0,
        0,
        0,
        0,
        0, 0, 0, 0, 
        16, 
        0,
        0,
        PFD_MAIN_PLANE, 
        0,
        0, 0, 0 
    };

    if (!(hDC=GetDC(glab.hWnd))) {
        MessageBox(NULL,"Can't Create A GL Device Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if (!(PixelFormat=ChoosePixelFormat(hDC,&pfd))) {
        MessageBox(NULL,"Can't Find A Suitable PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if(!SetPixelFormat(hDC,PixelFormat,&pfd)) {
        MessageBox(NULL,"Can't Set The PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if (!(hRC=wglCreateContext(hDC))) {
        MessageBox(NULL,"Can't Create A GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if(!wglMakeCurrent(hDC,hRC)) {
        MessageBox(NULL,"Can't Activate The GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    ShowWindow (glab.hWnd, nCmdShow);
    SetForegroundWindow(glab.hWnd);
    SetFocus(glab.hWnd);
    GL_ReSizeGLScene( w, h );

    if (!GL_init() ) {
        MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return false;
    }

    while (GetMessage (&messages, NULL, 0, 0)) {
        TranslateMessage(&messages);
        DispatchMessage(&messages);

        if( !GL_drawit() ) {
            MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
            return false;
        }
        SwapBuffers(hDC);
    }

    return messages.wParam;
}

GLvoid GL_ReSizeGLScene(GLsizei width, GLsizei height) {
    if (height==0) {
        height=1;
    }

    glViewport(0,0,width,height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

int GL_init( GLvoid ) {
    glShadeModel(GL_SMOOTH);
    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);
    glClearDepth(1.0f);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
    return true;
}

int GL_drawit( GLvoid ) {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glTranslatef(-1.5f,0.0f,-6.0f);
    glBegin(GL_TRIANGLES);
        glVertex3f( 0.0f, 1.0f, 0.0f);
        glVertex3f(-1.0f,-1.0f, 0.0f);
        glVertex3f( 1.0f,-1.0f, 0.0f);
    glEnd();            
    return true;
}

编辑:我还将您的GL_drawit() 调用移到了事件循环中，因此它会重新绘制以响应调整大小事件。好吧，任何事件都真的。