OpenGL核心配置文件不会纹理四边形

Posted 2023-02-22

【中文标题】OpenGL核心配置文件不会纹理四边形

【英文标题】：OpenGL Core Profile won't texture quad

【发布时间】：2014-09-14 02:02:11

【问题描述】：

我编写了以下代码来使用 GLFW 在两个不同的显示器上显示两个图像。当我尝试运行 OPENGL_CORE_PROFILE 时，它搞砸了，我的图像没有出现。

相反，屏幕只是保持黑色。但是当我不使用核心配置文件时，图像会很好地显示在屏幕上。我需要使用核心配置文件，以便可以使用 OpenGL 3.3 和 330 着色器。

我当前用来纹理四边形的方法是错误的吗？使用 OpenGL 3.3 显示和图像的最佳方法是什么？

#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/core/core.hpp>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <iostream>

static GLuint tex_lite;
static GLuint tex_dark;

static GLuint tex_front;
static GLuint tex_back;

float ratio;
int width, height;

char *textFileRead(char *fn) 


    FILE *fp;
    char *content = NULL;

    int count=0;

    if (fn != NULL) 
        fp = fopen(fn,"rt");

        if (fp != NULL) 

      fseek(fp, 0, SEEK_END);
      count = ftell(fp);
      rewind(fp);

            if (count > 0) 
                content = (char *)malloc(sizeof(char) * (count+1));
                count = fread(content,sizeof(char),count,fp);
                content[count] = '\0';
            
            fclose(fp);
        
    
    return content;


void printLog(GLuint obj)

    int infologLength = 0;
    int maxLength;

    if(glIsShader(obj))
        glGetShaderiv(obj,GL_INFO_LOG_LENGTH,&maxLength);
    else
        glGetProgramiv(obj,GL_INFO_LOG_LENGTH,&maxLength);

    char infoLog[maxLength];

    if (glIsShader(obj))
        glGetShaderInfoLog(obj, maxLength, &infologLength, infoLog);
    else
        glGetProgramInfoLog(obj, maxLength, &infologLength, infoLog);

    if (infologLength > 0)
        printf("%s\n",infoLog);


void image2texture(cv::Mat Image,GLuint &texName, int i)

    glClearColor (0.0, 0.0, 0.0, 0.0);
    glShadeModel(GL_FLAT);
    glEnable(GL_DEPTH_TEST);

    glActiveTexture(GL_TEXTURE0+i);
    glGenTextures(1, &texName);
    glBindTexture(GL_TEXTURE_2D, texName);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, 
                    GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, 
                    GL_NEAREST);

    glTexImage2D(GL_TEXTURE_2D, 0, 3, Image.cols, Image.rows, 0, GL_BGR,
                 GL_UNSIGNED_BYTE, Image.data);


static void error_callback(int error, const char* description)

    fputs(description, stderr);


GLuint linkShader(char* vert, char* frag)

    GLuint v,f,p;

    char *vs = NULL,*fs = NULL;

    v = glCreateShader(GL_VERTEX_SHADER);
    f = glCreateShader(GL_FRAGMENT_SHADER);

    vs = textFileRead(vert);
    fs = textFileRead(frag);

    const char * ff = fs;
    const char * vv = vs;

    glShaderSource(v, 1, &vv,NULL);
    glShaderSource(f, 1, &ff,NULL);

    free(vs);free(fs);

    glCompileShader(v);
    glCompileShader(f);

    p = glCreateProgram();
    glAttachShader(p,f);
    glAttachShader(p,v);

    glLinkProgram(p);

    return p;


static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)

    if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
        glfwSetWindowShouldClose(window, GL_TRUE);


void checkWindow(GLFWwindow* window)

    if (!window)
    
        glfwTerminate();
        exit(EXIT_FAILURE);
    


int main(void)

    GLFWwindow* window_back;
    GLFWwindow* window_front;

    glfwSetErrorCallback(error_callback);

    if ( !glfwInit() )
    
        exit(EXIT_FAILURE);
    

    cv::Mat image_lite = cv::imread("lena.tiff");
    cv::Mat image_dark = cv::imread("lena.tiff");

    cv::flip(image_lite, image_lite, 0);
    cv::flip(image_dark, image_dark, 0);

    int count;
    GLFWmonitor** monitors = glfwGetMonitors(&count);

    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    if (count >= 2)
    
        window_front = glfwCreateWindow(1680,1050,"Front Screen",monitors[0],NULL);
        window_back = glfwCreateWindow(1280,800,"Back Screen",monitors[1],NULL);
        glewInit();
    
    else
    
        exit(EXIT_FAILURE);
    

    checkWindow(window_front);
    checkWindow(window_back);

    glfwMakeContextCurrent(window_front);
    glfwSetKeyCallback(window_front, key_callback);

    glewExperimental = GL_TRUE;
    GLenum err = glewInit();
    if(err!=GLEW_OK)
    
        std::cout<<"glewInit failed, aborting."<<std::endl;
    

    std::cout << glGetString(GL_RENDERER) << std::endl;
    std::cout << glGetString(GL_VENDOR) << std::endl;
    std::cout << glGetString(GL_VERSION) << std::endl;
    std::cout << glGetString(GL_SHADING_LANGUAGE_VERSION) << std::endl;

    while (!glfwWindowShouldClose(window_front) && !glfwWindowShouldClose(window_back))
    

        glfwMakeContextCurrent(window_front);
        glfwSetKeyCallback(window_front, key_callback);

        glfwGetFramebufferSize(window_front, &width, &height);
        ratio = width / (float) height;
        glViewport(0,0,width,height);

        image2texture(image_lite, tex_lite,0);

        // GLuint prg = linkShader("toon.vert","toon.frag");

        glClear(GL_COLOR_BUFFER_BIT);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(-ratio,ratio,-1.f,1.f,-1.f,1.f);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();

        glActiveTexture(GL_TEXTURE0);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glEnable(GL_TEXTURE_2D);
        glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
        glBindTexture(GL_TEXTURE_2D, tex_lite);

        glBegin(GL_QUADS);
            glTexCoord2f(0.0, 0.0); glVertex3f(-1.0,-1.0,0.0);
            glTexCoord2f(0.0, 1.0); glVertex3f(-1.0,1.0,0.0);
            glTexCoord2f(1.0, 1.0); glVertex3f(1.0,1.0,0.0);
            glTexCoord2f(1.0, 0.0); glVertex3f(1.0,-1.0,0.0);
        glEnd();     
        glFlush();
        glfwSwapBuffers(window_front);
        glfwPollEvents();

        glfwMakeContextCurrent(window_back);
        glfwSetKeyCallback(window_back, key_callback);

        glfwGetFramebufferSize(window_back, &width, &height);
        ratio = width / (float) height;
        glViewport(0,0,width,height);

        image2texture(image_dark, tex_dark,1);

        glClear(GL_COLOR_BUFFER_BIT);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(-ratio,ratio,-1.f,1.f,-1.f,1.f);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();

        glActiveTexture(GL_TEXTURE0);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glEnable(GL_TEXTURE_2D);
        glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
        glBindTexture(GL_TEXTURE_2D, tex_lite);

        glBegin(GL_QUADS);
            glTexCoord2f(0.0, 0.0); glVertex3f(-1.0,-1.0,0.0);
            glTexCoord2f(0.0, 1.0); glVertex3f(-1.0,1.0,0.0);
            glTexCoord2f(1.0, 1.0); glVertex3f(1.0,1.0,0.0);
            glTexCoord2f(1.0, 0.0); glVertex3f(1.0,-1.0,0.0);
        glEnd();
        glFlush();
        glfwSwapBuffers(window_back);
        glfwPollEvents();
    
    glfwMakeContextCurrent(window_front);
    glfwDestroyWindow(window_front);
    glfwMakeContextCurrent(window_back);
    glfwDestroyWindow(window_back);

    glfwTerminate();
    exit(EXIT_SUCCESS);

【参考方案1】：

您的代码在核心配置文件中完全无效。在核心配置文件中，所有多年前已宣布“弃用”的旧功能实际上已删除。不支持GL_QUADS 原始类型，不支持使用glBegin()/glEnd() 的即时模式渲染，不支持glEnable(GL_TEXTURE_2D);，不支持texcoord 和顶点位置等内置顶点属性，不支持GL_TEXTURE_ENV_MODE，不支持着色器渲染（“固定功能管道”）不支持。 glMatrixMode()、glLoadIdentity、glOrtho() 和所有其他矩阵和矩阵堆栈相关的函数也是如此。 glTexImage2D() 也不支持内部格式“3”，您应该使用GL_RGB（您之前也应该使用过）。

当您想使用现代核心配置文件时，您必须使用带有着色器且没有所有内置属性的可编程管道。您可以改为定义自己的通用属性。您必须对几何图形使用 VBO，对顶点指针使用 VAO，而不是立即模式。您还必须用基于三角形的图元替换四边形图元。您将不得不使用自己的矩阵函数，或者为此使用一些库。

您可能想看看像 arcsynthesis 或 open.gl 这样专门处理现代 OpenGL 的教程。