Packt 学习OpenGL教程，渲染三角形时出现段错误。与GLchar * vertexShaderSource和GLchar *fragmentShaderSource相关？

问题描述 投票：0回答：1

我在上一个由 packt 学习 OpenGL 的示例中制作了一个橙色三角形。当我使用shader.h、core.vs和core.frag将代码更新到下一个示例时，我编译得很好，但出现了段错误。和

GLchar * fragmentShaderSource
和
GLchar * vertexShaderSource
有关系吗？我注意到它们被从 
colouredtriangle.cpp
中取出，#version 330 核心被移至 
core.frag
和 
core.vs
中。我收到一个错误，它们没有定义，所以我把它们放回去。我有：

#include <iostream>
#define GLEW_STATIC
#include "shader.h"
#include <GL/glew.h>
#include <GLFW/glfw3.h>

Shader ourShader("core.vs", "core.frag");

const GLchar *vertexShaderSource = "#version 330 core\n";

const GLchar *fragmentShaderSource = "#version 330 core\n";

const GLuint WIDTH = 800, HEIGHT = 600;

int main() {
  glfwInit();

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

  glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);

  GLFWwindow *window =
      glfwCreateWindow(WIDTH, HEIGHT, "Learn OpenGL", nullptr, nullptr);

  int screenWidth, screenHeight;

  glfwGetFramebufferSize(window, &screenWidth, &screenHeight);

  if (nullptr == window) {
    std::cout << "Failed to create glfw window!\n";
    glfwTerminate();

    return EXIT_FAILURE;
  }

  glfwMakeContextCurrent(window);

  glewExperimental = GL_TRUE;

  if (GLEW_OK != glewInit()) {
    std::cout << "Failed to initialize glew!" << std::endl;

    return EXIT_FAILURE;
  }

  glViewport(0, 0, screenWidth, screenHeight);
  GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
  glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);

  glCompileShader(vertexShader);
  GLint success;
  GLchar infoLog(512);

  glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);

  if (!success) {
    glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
    std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED" << infoLog
              << std::endl;
  }

  GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
  glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
  glCompileShader(fragmentShader);
  glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);

  if (!success) {
    glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
    std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION::FAILED\n"
              << infoLog << std::endl;
  }

  GLuint shaderProgram = glCreateProgram();
  glAttachShader(shaderProgram, vertexShader);
  glAttachShader(shaderProgram, fragmentShader);
  glLinkProgram(shaderProgram);

  glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);

  if (!success) {
    glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
    std::cout << "ERROR::SHADER::PROGRAM::LINKING::FAILED\n"
              << infoLog << std::endl;
  }

  glDeleteShader(vertexShader);
  glDeleteShader(fragmentShader);

  GLfloat vertices[] = {0.5f, -0.5f, 0.0f, -0.5f, -0.5f,
                        0.0f, 0.0f,  0.5f, 0.0f};

  GLuint VBO, VAO;
  glGenVertexArrays(1, &VAO);
  glGenBuffers(1, &VBO);

  glBindVertexArray(VAO);
  glBindBuffer(GL_ARRAY_BUFFER, VBO);
  glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat),
                        (GLvoid *)0);
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat),
                        (GLvoid *)(3 * sizeof(GLfloat)));

  glBindVertexArray(0);

  while (!glfwWindowShouldClose(window)) {
    glfwPollEvents();
    glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    ourShader.Use();
    glBindVertexArray(VAO);
    glDrawArrays(GL_TRIANGLES, 0, 3);
    glBindVertexArray(0);

    glfwSwapBuffers(window);
  }

  glDeleteVertexArrays(1, &VAO);
  glDeleteBuffers(1, &VBO);

  glfwTerminate();

  return EXIT_SUCCESS;
}

着色器.h

#ifndef SHADER_H
#define SHADER_H
#include <GL/glew.h>
#include <fstream>
#include <iostream>
#include <sstream>
#include <string>

class Shader {
public:
  GLuint Program;
  Shader(const GLchar *vertexPath, const GLchar *fragmentPath) {

    std::string vertexCode;
    std::string fragmentCode;
    std::ifstream vShaderFile;
    std::ifstream fShaderFile;

    vShaderFile.exceptions(std::ifstream::badbit);
    fShaderFile.exceptions(std::ifstream::badbit);

    try {
      vShaderFile.open(vertexPath);
      fShaderFile.open(fragmentPath);
      std::stringstream vShaderStream, fShaderStream;
      vShaderStream << vShaderFile.rdbuf();
      fShaderStream << fShaderFile.rdbuf();
      vShaderFile.close();
      fShaderFile.close();
      vertexCode = vShaderStream.str();
      fragmentCode = fShaderStream.str();
    } catch (std::ifstream::failure e) {
      std::cout << "ERROR::SHADER::FILE_NOT_SUCCESSFULLY_READ" << std::endl;
    }

    const GLchar *vShaderCode = vertexCode.c_str();
    const GLchar *fShaderCode = fragmentCode.c_str();

    GLuint vertex, fragment;
    GLint success;
    GLchar infoLog[512];

    vertex = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertex, 1, &vShaderCode, NULL);
    glCompileShader(vertex);
    glGetShaderiv(vertex, GL_COMPILE_STATUS, &success);
    if (!success) {
      glGetShaderInfoLog(vertex, 512, NULL, infoLog);
      std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED" << infoLog
                << std::endl;
    }

    this->Program = glCreateProgram();
    glAttachShader(this->Program, vertex);
    glAttachShader(this->Program, fragment);
    glLinkProgram(this->Program);

    glGetProgramiv(this->Program, GL_LINK_STATUS, &success);
    if (!success) {
      glGetProgramInfoLog(this->Program, 512, NULL, infoLog);
      std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n"
                << infoLog << std::endl;
    }

    glDeleteShader(vertex);
    glDeleteShader(fragment);
  }

  void Use() { glUseProgram(this->Program); }
};
#endif

核心.fs

#version 330 core
in vec3 ourColor;
out vec4 color;
void main()
{ 
  color vec4(ourColor, 1.0f);
}

核心.vs

#version 330 core

layout (location = 0) in vec3 position;
layout (location = 1) in vec3 color;"
out vec3 ourColor"
void main()
{
    glPosition = vec 4 (position, 1.0f);
    ourColor = color;}"
c++ opengl glfw
1个回答
1
投票

变量 

vertexShaderSource
和 
fragmentShaderSource
似乎未正确初始化，因为它们不是完整的着色器源，但分段错误与这些变量无关 - 它发生得更早。

主要问题是

ourShader
类型的
Shader
是在文件（全局）范围内声明的，因此它的构造函数在
main
函数之前运行。 Shader的构造函数使用的
OpenGL函数指针
在此时尚未初始化，并且仅在GLEW初始化后才会被初始化。该程序当前将尝试使用位于内存位置 0x0 等处的函数指针，这会导致分段错误。

解决方案是在

Shader ourShader(...)调用之后将

glewInit()
移动到。此外，具有 main 函数的文件和着色器类都包含从着色器源创建着色器程序的代码。假设这个想法是为此使用一个单独的类，请删除代码 
after
将视口设置为 before 从主文件定义顶点。现在也可以删除变量 vertexShaderSource 和 
fragmentShaderSource
。它们的内容没有用，从文件读取着色器源到链接着色器程序的所有内容现在都由 Shader 类处理。


有关 OpenGL 渲染的其他问题：




片段着色器源在 
    =
  1.  之后缺少 
    color
    ，
    glPosition
     应为 
    gl_Position
    。
    顶点着色器源有几个额外的引号 (
    2. "
  2. )，并且在 
    ourColor
     后面缺少一个分号。
    缺少编译片段着色器的代码。
    3. 

  3. vertices
  4. 的定义中缺少颜色信息。
    位置 1 处的属性（颜色）未启用。
    5. 

  5. 

    6. 更正来源：


主文件：


#include <iostream>

#define GLEW_STATIC
#include <GL/glew.h>

#include <GLFW/glfw3.h>

#include "shader.h"

const GLuint WIDTH = 800, HEIGHT = 600;

int main()
{
    glfwInit();

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

    glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);

    GLFWwindow *window = glfwCreateWindow (WIDTH, HEIGHT, "Learn OpenGL", nullptr, nullptr);

    int screenWidth, screenHeight;
    glfwGetFramebufferSize(window, &screenWidth, &screenHeight);

    if (nullptr == window)
    {
        std::cout<<"Failed to create glfw window!\n";
        glfwTerminate();
        return EXIT_FAILURE;
    }

    glfwMakeContextCurrent(window);

    glewExperimental = GL_TRUE;

    if (GLEW_OK != glewInit())
    {
        std::cout<<"Failed to initialize glew!"<<std::endl;
        return EXIT_FAILURE;
    }

    Shader ourShader ("core.vs", "core.frag");

    glViewport(0, 0, screenWidth, screenHeight);

    GLfloat vertices[] =
    {
        0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.0f,
        -0.5f, -0.5f, 0.0f, 0.0f, 1.0f, 0.0f,
        0.0f, 0.5f, 0.0f, 0.0f, 0.0f, 1.0f
    };

    GLuint VBO, VAO;
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);

    glBindVertexArray(VAO);
    glBindBuffer(GL_ARRAY_BUFFER,VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE, 6 * sizeof(GLfloat), (GLvoid *) 0);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(1,3,GL_FLOAT,GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*) (3 * sizeof(GLfloat)));
    glEnableVertexAttribArray(1);

    glBindVertexArray(0);

    while (!glfwWindowShouldClose(window))
    {
        glfwPollEvents();
        glClearColor(0.2f,0.3f,0.3f,1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        ourShader.Use();
        glBindVertexArray(VAO);
        glDrawArrays(GL_TRIANGLES, 0, 3);
        glBindVertexArray(0);

        glfwSwapBuffers(window);
    }

    glDeleteVertexArrays(1,&VAO);
    glDeleteBuffers(1,&VBO);

    glfwTerminate();

    return EXIT_SUCCESS;
}



着色器.h


#ifndef SHADER_H
#define SHADER_H

#include <string>
#include <fstream>
#include <sstream>
#include <iostream>
#include <GL/glew.h>

class Shader
{
public:
    GLuint Program;
    Shader(const GLchar * vertexPath, const GLchar * fragmentPath)
    {
        std::string vertexCode;
        std::string fragmentCode;
        std::ifstream vShaderFile;
        std::ifstream fShaderFile;

        vShaderFile.exceptions(std::ifstream::badbit);
        fShaderFile.exceptions(std::ifstream::badbit);

        try
        {
            vShaderFile.open(vertexPath);
            fShaderFile.open(fragmentPath);
            std::stringstream vShaderStream, fShaderStream;
            vShaderStream << vShaderFile.rdbuf();
            fShaderStream << fShaderFile.rdbuf();
            vShaderFile.close();
            fShaderFile.close();
            vertexCode = vShaderStream.str();
            fragmentCode = fShaderStream.str();
        }
        catch(std::ifstream::failure e)
        {
            std::cout<<"ERROR::SHADER::FILE_NOT_SUCCESSFULLY_READ"<<std::endl;
        }

        const GLchar * vShaderCode = vertexCode.c_str();
        const GLchar * fShaderCode = fragmentCode.c_str();

        GLuint vertex, fragment;
        GLint success;
        GLchar infoLog[512];

        vertex = glCreateShader(GL_VERTEX_SHADER);
        glShaderSource(vertex, 1, &vShaderCode, NULL);
        glCompileShader(vertex);
        glGetShaderiv(vertex, GL_COMPILE_STATUS, &success);
        if(!success)
        {
            glGetShaderInfoLog(vertex, 512, NULL, infoLog);
            std::cout<<"ERROR::SHADER::VERTEX::COMPILATION_FAILED"<<infoLog<<std::endl;
        }

        fragment = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(fragment, 1, &fShaderCode, NULL);
        glCompileShader(fragment);
        glGetShaderiv(fragment, GL_COMPILE_STATUS, &success);
        if(!success)
        {
            glGetShaderInfoLog(fragment, 512, NULL, infoLog);
            std::cout<<"ERROR::SHADER::VERTEX::COMPILATION_FAILED"<<infoLog<<std::endl;
        }

        this->Program = glCreateProgram();
        glAttachShader(this->Program, vertex);
        glAttachShader(this->Program, fragment);
        glLinkProgram(this->Program);

        glGetProgramiv(this->Program, GL_LINK_STATUS, &success);
        if(!success)
        {
            glGetProgramInfoLog(this->Program,512,NULL,infoLog);
            std::cout<<"ERROR::SHADER::PROGRAM::LINKING_FAILED\n"<<infoLog<<std::endl;
        }

        glDeleteShader(vertex);
        glDeleteShader(fragment);
    }

    void Use()
    {
        glUseProgram(this->Program);
    }
};

#endif



核心.vs


#version 330 core

layout (location = 0) in vec3 position;
layout (location = 1) in vec3 color;

out vec3 ourColor;

void main()
{
    gl_Position = vec4(position, 1.0f);
    ourColor = color;
}



核心.fs


#version 330 core

in vec3 ourColor;
out vec4 color;

void main()
{
    color = vec4(ourColor, 1.0f);
}



我修改了格式并为顶点选择了不同的任意颜色。

    

	

    

    


  

  

    
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