c++ - Linux 上的黑屏，但 Windows 上没有

Question

我使用 OpenGL（GLEW 和 GLFW 库）在 C++ 中编写了一个程序，该程序将红色三角形呈现到窗口。我在 Windows 10 上对其进行了测试，但是当我在 Linux (Ubuntu) 上尝试时，它会打开一个只有黑色且没有三角形的窗口。在编译/链接阶段，我没有收到任何错误。我正在使用 NVIDIA 的专有驱动程序。可能是什么问题呢？

这是我的代码：

#include <GL/glew.h>
#include <GLFW/glfw3.h>
 
#include <iostream>
 
static unsigned int CompileShader(unsigned int type, const std::string &source) {
    unsigned int id = glCreateShader(type);
    const char *src = source.c_str();
    glShaderSource(id, 1, &src, nullptr);
    glCompileShader(id);
 
    int result;
    glGetShaderiv(id, GL_COMPILE_STATUS, &result);
    if (result == GL_FALSE) {
        int length;
        glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
        char *message = (char*)alloca(length * sizeof(char));
        glGetShaderInfoLog(id, length, &length, message);
        std::cout << "Failed to compile " << (type == GL_VERTEX_SHADER ? "vertex" : "fragment") << "shader" << std::endl;
        std::cout << message << std::endl;
        glDeleteShader(id);
        return 0;
    }
 
    return id;
}
 
static unsigned int CreateShader(const std::string &vertexShader, const std::string &fragmentShader) {
    unsigned int program = glCreateProgram();
    unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
    unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);
 
    glAttachShader(program, vs);
    glAttachShader(program, fs);
    glLinkProgram(program);
    glValidateProgram(program);
 
    glDeleteShader(vs);
    glDeleteShader(fs);
 
    return program;
}
 
int main(void)
{
    GLFWwindow *window;
 
    /* Initialize the library */
    if (!glfwInit()) {
        std::cout << "Error initialising glfw3!" << std::endl;
        return -1;
    }
 
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
 
    window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
    if (!window)
    {
        std::cout << "Error initialising a window!" << std::endl;
        glfwTerminate();
        return -1;
    }
 
    glfwMakeContextCurrent(window);
 
    if (glewInit() != GLEW_OK) {
        std::cout << "Error initialising GLEW!" << std::endl;
        return -1;
    }
 
    std::cout << glGetString(GL_VERSION) << std::endl;
 
    float positions[6] = {
        -0.5f, -0.5f,
         0.0f,  0.5f,
         0.5f, -0.5f
    };
 
    unsigned int buffer;
    glGenBuffers(1, &buffer);
    glBindBuffer(GL_ARRAY_BUFFER, buffer);
    glBufferData(GL_ARRAY_BUFFER, 6 * sizeof(float), positions, GL_STATIC_DRAW);
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(float), 0);
    glEnableVertexAttribArray(0);
 
    std::string vertexShader =
        "#version 330 core\n"
        "\n"
        "layout(location = 0) in vec4 position;\n"
        "\n"
        "void main()\n"
        "{\n"
        "   gl_Position = position;\n"
        "}\n";
 
    std::string fragmentShader =
        "#version 330 core\n"
        "\n"
        "layout(location = 0) out vec4 color;\n"
        "\n"
        "void main()\n"
        "{\n"
        "   color = vec4(1.0, 0.0, 0.0, 1.0);\n"
        "}\n";
 
    unsigned int shader = CreateShader(vertexShader, fragmentShader);
    glUseProgram(shader);
 
    /* Loop until the user closes the window */
    while (!glfwWindowShouldClose(window))
    {
        glClear(GL_COLOR_BUFFER_BIT);
 
        glDrawArrays(GL_TRIANGLES, 0, 3);
 
        glfwSwapBuffers(window);
 
        glfwPollEvents();
    }
 
    glDeleteProgram(shader);
    glfwTerminate();
    return 0;
}

编译代码：

g++ -std=c++17 main.cpp -Wall  -lGL -lGLU -lGLEW -lglfw3 -lX11 -lXxf86vm -lXrandr -lpthread -lXi -ldl -lXinerama -lXcursor -o main

标签： c++linuxopenglglfwglew

Answer 1

核心上下文需要在渲染任何东西之前绑定一个顶点数组对象（VAO） 。

如果您不想花哨，可以在程序开始时创建一个 VAO 并将其绑定：

GLuint vao = 0;
glCreateVertexArrays( 1, &vao );
glBindVertexArray( vao );
...
glDrawArrays(GL_TRIANGLES, 0, 3);

全部一起：

#include <GL/glew.h>
#include <GLFW/glfw3.h>

#include <iostream>

static unsigned int CompileShader(unsigned int type, const std::string &source) {
    unsigned int id = glCreateShader(type);
    const char *src = source.c_str();
    glShaderSource(id, 1, &src, nullptr);
    glCompileShader(id);

    int result;
    glGetShaderiv(id, GL_COMPILE_STATUS, &result);
    if (result == GL_FALSE) {
        int length;
        glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
        char *message = (char*)alloca(length * sizeof(char));
        glGetShaderInfoLog(id, length, &length, message);
        std::cout << "Failed to compile " << (type == GL_VERTEX_SHADER ? "vertex" : "fragment") << "shader" << std::endl;
        std::cout << message << std::endl;
        glDeleteShader(id);
        return 0;
    }

    return id;
}

static unsigned int CreateShader(const std::string &vertexShader, const std::string &fragmentShader) {
    unsigned int program = glCreateProgram();
    unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
    unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);

    glAttachShader(program, vs);
    glAttachShader(program, fs);
    glLinkProgram(program);
    glValidateProgram(program);

    glDeleteShader(vs);
    glDeleteShader(fs);

    return program;
}

int main(void)
{
    GLFWwindow *window;

    /* Initialize the library */
    if (!glfwInit()) {
        std::cout << "Error initialising glfw3!" << std::endl;
        return -1;
    }

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

    window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
    if (!window)
    {
        std::cout << "Error initialising a window!" << std::endl;
        glfwTerminate();
        return -1;
    }

    glfwMakeContextCurrent(window);

    if (glewInit() != GLEW_OK) {
        std::cout << "Error initialising GLEW!" << std::endl;
        return -1;
    }

    std::cout << glGetString(GL_VERSION) << std::endl;

    float positions[6] = {
        -0.5f, -0.5f,
         0.0f,  0.5f,
         0.5f, -0.5f
    };

    GLuint vao = 0;
    glCreateVertexArrays( 1, &vao );
    glBindVertexArray( vao );

    unsigned int buffer;
    glGenBuffers(1, &buffer);
    glBindBuffer(GL_ARRAY_BUFFER, buffer);
    glBufferData(GL_ARRAY_BUFFER, 6 * sizeof(float), positions, GL_STATIC_DRAW);
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(float), 0);
    glEnableVertexAttribArray(0);

    std::string vertexShader =
        "#version 330 core\n"
        "\n"
        "layout(location = 0) in vec4 position;\n"
        "\n"
        "void main()\n"
        "{\n"
        "   gl_Position = position;\n"
        "}\n";

    std::string fragmentShader =
        "#version 330 core\n"
        "\n"
        "layout(location = 0) out vec4 color;\n"
        "\n"
        "void main()\n"
        "{\n"
        "   color = vec4(1.0, 0.0, 0.0, 1.0);\n"
        "}\n";

    unsigned int shader = CreateShader(vertexShader, fragmentShader);
    glUseProgram(shader);

    /* Loop until the user closes the window */
    while (!glfwWindowShouldClose(window))
    {
        glClear(GL_COLOR_BUFFER_BIT);

        glDrawArrays(GL_TRIANGLES, 0, 3);

        glfwSwapBuffers(window);

        glfwPollEvents();
    }

    glDeleteProgram(shader);
    glfwTerminate();
    return 0;
}