遵循教程后 OpenGL 不渲染任何东西

Question

我最近开始在 youtube 上关注 TheCherno 的 OpenGL 教程系列。
这是我的代码：

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

#include <iostream>
#include <fstream>
#include <string>
#include <sstream>

struct ShaderProgramSource {
    std::string VertexSource;
    std::string FragmentSource;
};

static ShaderProgramSource ParseShader(const std::string& filepath) {
    std::ifstream stream(filepath);

    enum class ShaderType {
        NONE = -1, VERTEX = 0, FRAGMENT = 1
    };

    std::string line;
    std::stringstream ss[2];
    ShaderType type = ShaderType::NONE;
    while (getline(stream, line)) {

        if (line.find("#shader") != std::string::npos) {

            if (line.find("vertex") != std::string::npos)
                type = ShaderType::VERTEX;
            else if (line.find("fragment") != std::string::npos)
                type = ShaderType::FRAGMENT;

        } else {
            ss[(int)type] << line << '\n';
        }
    }

    return { ss[0].str(), ss[1].str() };
}

static unsigned int CompileShader(unsigned int type, const std::string& source) {

    std::cout << "Compiling " << (type == GL_VERTEX_SHADER ? "vertex" : "fragment") << " shader..." << std::endl;

    unsigned int id = glCreateShader(type);
    const char* src = source.c_str();
    glShaderSource(id, 1, &src, nullptr);
    std::cout << glGetError() << std::endl;

    glCompileShader(id);
    std::cout << glGetError() << std::endl;

    int result;
    glGetShaderiv(id, GL_COMPILE_STATUS, &result);
    std::cout << glGetError() << std::endl;

    if (result == GL_FALSE) {
        int length;
        glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
        std::cout << glGetError() << std::endl;

        char* message = (char*)alloca(length * sizeof(char));
        glGetShaderInfoLog(id, length, &length, message);
        std::cout << glGetError() << std::endl;

        std::cout << "Failed to compile" << (type == GL_VERTEX_SHADER ? "vertex" : "fragment") << " shader!" << std::endl;
        std::cout << message << std::endl;
        glDeleteShader(id);
        std::cout << glGetError() << std::endl;

        return 0;
    }

    std::cout << "Successfully compiled " << (type == GL_VERTEX_SHADER ? "vertex" : "fragment") << " shader!" << std::endl << std::endl;
    return id;
}

static unsigned int CreateShader(const std::string& vertexShader, const std::string& fragmentShader) {

    std::cout << "Creating shader..." << std::endl << std::endl;
    
    unsigned int program = glCreateProgram();
    unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
    unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);

    glAttachShader(program, vs);
    std::cout << glGetError() << std::endl;
    std::cout << "Attached vertex shader" << std::endl;

    glAttachShader(program, fs);
    std::cout << glGetError() << std::endl;
    std::cout << "Attached fragment shader" << std::endl;

    glLinkProgram(program);
    std::cout << glGetError() << std::endl;
    glValidateProgram(program);
    std::cout << glGetError() << std::endl;
    std::cout << "Linked and validated program" << std::endl;

    glDeleteShader(vs);
    std::cout << glGetError() << std::endl;
    std::cout << "Deleted vertex shader" << std::endl;

    glDeleteShader(fs);
    std::cout << glGetError() << std::endl;
    std::cout << "Deleted fragment shader" << std::endl;

    std::cout << "Succesfully created shader!" << std::endl << std::endl;

    return program;
}

int main(void)
{
    GLFWwindow* window;

    /* Initialize the library */
    if (!glfwInit())
        return -1;

    /* Create a windowed mode window and its OpenGL context */
    window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
    if (!window)
    {
        glfwTerminate();
        return -1;
    }

    /* Make the window's context current */
    glfwMakeContextCurrent(window);

    if (glewInit() != GLEW_OK) {
        std::cout << "Error!" << std::endl;
    }

    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);
    std::cout << glGetError() << std::endl;
    glBindBuffer(GL_ARRAY_BUFFER, buffer);
    std::cout << glGetError() << std::endl;
    glBufferData(GL_ARRAY_BUFFER, 6*sizeof(float), positions, GL_STATIC_DRAW);
    std::cout << glGetError() << std::endl;

    glDisableVertexAttribArray(0);
    std::cout << glGetError() << std::endl;
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(float)*2, 0);
    std::cout << glGetError() << std::endl;

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    std::cout << glGetError() << std::endl;
    
    ShaderProgramSource source = ParseShader("res/shaders/Basic.shader");
    std::cout << "VERTEX" << std::endl;
    std::cout << source.VertexSource << std::endl;
    std::cout << "FRAGMENT" << std::endl;
    std::cout << source.FragmentSource << std::endl;

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


    
    // render loop
    while (!glfwWindowShouldClose(window))
    {
        /* Render here */
        glClear(GL_COLOR_BUFFER_BIT);

        glDrawArrays(GL_TRIANGLES, 0, 3);

        /* Swap front and back buffers */
        glfwSwapBuffers(window);

        /* Poll for and process events */
        glfwPollEvents();
    }

    //glDeleteProgram(shader);

    glfwTerminate();
    return 0;
}

这是 Basic.shader 文件：

#shader vertex
#version 330 core  

layout(location = 0) in vec4 position;  

void main()  
{  
    gl_Position = position;  
}

#shader fragment
#version 330 core  

layout(location = 0) out vec4 color;  

void main()  
{  
    color = vec4(1.0, 0.0, 0.0, 1.0);  
}

我试过使用 glGetError 并且它没有输出任何错误。

Answer 1

您需要启用通用顶点属性数组而不是禁用它（参见 glEnableVertexAttribArray）：

~~glDisableVertexAttribArray(0);~~

glEnableVertexAttribArray(0);

另外，将sahder的编译链接安装代码注释掉：

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

unsigned int shader = CreateShader(source.VertexSource, source.FragmentSource);
glUseProgram(shader);

Answer 2

我相信@Rabbid76 的回答是正确的。如果它仍然不起作用，请确保您使用的是兼容的 OpenGL 上下文或创建一个 VAO 来保存状态。

兼容的 OpenGL 上下文可以设置为：

//Before glfwCreateWindow call, after glfwInit
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_COMPAT_PROFILE);

默认值为 GLFW_OPENGL_ANY_PROFILE，如果 COMPAT 不可用，这可能意味着 CORE。这确保默认 VAObject 始终存在并被绑定。这意味着您的 glVertexAttribPointer 调用实际上有一个地方可以存储该信息。我没有看到 Cherno 的这些教程，未来的教程很可能会介绍 VAO。在 CORE 中不会有，也可能不会画任何东西。

虽然我们在这里，但准确设置所需的最小 OpenGL 版本并不是一个坏主意。如果由于某种原因它在目标机器上不可用，window 创建将失败。这比调用不受支持的函数时出现“随机”段错误更可取。

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

我的首选方法是创建一个实际的 VAO 并使用 GLFW_OPENGL_CORE_PROFILE。不过请放心去学习教程，我从他那里看到的那些真的是high-quality。

//Put these before the vertex buffer initialization
int VAO;
glGenVertexArrays(1,&VAO);
glBindVertexArray(VAO);

遵循教程后 OpenGL 不渲染任何东西

OpenGL not rendering anything after following tutorial

c++

opengl

shader

glsl

glfw