在 opengl 中画出三角形并用 shader 改变颜色

/*
glew.h 源代码中的一些宏定义
typedef unsigned int GLenum;
typedef unsigned int GLbitfield;
typedef unsigned int GLuint;
typedef int GLint;
typedef int GLsizei;
typedef unsigned char GLboolean;
typedef signed char GLbyte;
typedef short GLshort;
typedef unsigned char GLubyte;
typedef unsigned short GLushort;
typedef unsigned long GLulong;
typedef float GLfloat;
typedef float GLclampf;
typedef double GLdouble;
typedef double GLclampd;
typedef void GLvoid;
 */

#include 

#define GLEW_STATIC

#include 
#include 

void key_callback(GLFWwindow *windows, int key, int scancode, int actin, int mode);

const GLuint WIDTH = 800, HEIGHT = 600;

//Shaders
const GLchar *vertexShaderSource = "#version 330 core\n"
        "  \n"
        "layout (location = 0) in vec3 position;\n"
        "\n"
        "void main()\n"
        "{\n"
        "    gl_Position = vec4(position.x, position.y, position.z, 1.0);\n"
        "}";


const GLchar *fragmentShaderSource = "#version 330 core\n"
        "out vec4 color;\n"
        "void main()\n"
        "{\n"
        "color = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
        "}\n\0";
const GLchar* fragmentShaderSource2 = "#version 330 core\n"
        "out vec4 color;\n"
        "void main()\n"
        "{\n"
        "color = vec4(1.0f, 1.0f, 0.0f, 1.0f); // The color yellow \n"
        "}\n\0";

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_RESIZABLE, GL_FALSE);

    //返回指向 GLFWwindow 对象的指针，参数有五个，前两个是高和宽，中间是窗口的名字，后两个是模式和共享的选项，
    //现在都是 null， 注意 nullptr 是 c++11 的语法
    GLFWwindow *window = glfwCreateWindow(WIDTH, HEIGHT, "OpenGL", nullptr, nullptr);
    glfwMakeContextCurrent(window);  //用 GLFW 在当前现成创建主环境

    glewExperimental = GL_TRUE;//将其设为 true 来使 glew 用更新的技术来处理 opengl 函数

    glewInit();//初始化glew

    //用 viewport 来定义尺寸来使其能在高 dpi 屏幕上也能正常工作
    int width, height;
    glfwGetFramebufferSize(window, &width, &height);
    glViewport(0, 0, width, height);

    //创建 vertexShader,glShaderSource 将 shader 的代码给定到指定的 shader 中，返回对象的 ID
    //glCompileShader 来编译.
    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);

    //当编译 Shader 错误时报错
    GLint success;
    GLchar infoLog[512];
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if (!success) {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

    // Fragment shader ，同上
    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    glCompileShader(fragmentShader);
    // 检查编译错误
    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
    if (!success) {
        glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

    // Fragment shader ，同上
    GLuint fragmentShader2 = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader2, 1, &fragmentShaderSource2, NULL);
    glCompileShader(fragmentShader2);
    // Check for compile time errors
    glGetShaderiv(fragmentShader2, GL_COMPILE_STATUS, &success);
    if (!success) {
        glGetShaderInfoLog(fragmentShader2, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

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

    //检查 link 是否出错
    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
    }

    GLuint shaderProgram2 = glCreateProgram();
    glAttachShader(shaderProgram2, vertexShader);
    glAttachShader(shaderProgram2, fragmentShader2);
    glLinkProgram(shaderProgram2);

    //检查 link 是否出错
    glGetProgramiv(shaderProgram2, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(shaderProgram2, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
    }

    //用完后删除 Shader
    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);
    glDeleteShader(fragmentShader2);

    //定义点数据
    GLfloat vertices1[] = {
            0.0f, -0.5f, 0.0f,
            1.0f, -0.5f, 0.0f,
            0.5f, 0.5f, 0.0f,
    };

    GLfloat vertices2[] = {
            0.0f, -0.5f, 0.0f,
            -1.0, -0.5f, 0.0f,
            -0.5f, 0.5f, 0.0f
    };
    GLuint VBOs[2], VAOs[2];
    //第一个三角形
    glGenVertexArrays(1, &VAOs[0]);
    glGenBuffers(1, &VBOs[0]);

    glBindVertexArray(VAOs[0]);

    glBindBuffer(GL_ARRAY_BUFFER, VBOs[0]); //绑定 VBO
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices1), vertices1, GL_STATIC_DRAW);//将定义好的点放入缓存中,
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat),
                          (GLvoid *) 0);//定义如何使用点数据，第一个参数是 location，确定我们要设置哪些点属性
    glEnableVertexAttribArray(0); //使 location 为 0 的点可以使用属性，默认是关闭的

    glBindBuffer(GL_ARRAY_BUFFER, 0);//解绑 VBO
    glBindVertexArray(0);//解绑 VAO

    //第二个三角形
    glGenVertexArrays(1, &VAOs[1]);
    glGenBuffers(1, &VBOs[1]);

    glBindVertexArray(VAOs[1]);

    glBindBuffer(GL_ARRAY_BUFFER, VBOs[1]); //绑定 VBO
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_DRAW);//将定义好的点放入缓存中,
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat),
                          (GLvoid *) 0);//定义如何使用点数据，第一个参数是 location，确定我们要设置哪些点属性
    glEnableVertexAttribArray(0); //使 location 为 0 的点可以使用属性，默认是关闭的

    glBindBuffer(GL_ARRAY_BUFFER, 0);//解绑 VBO
    glBindVertexArray(0);//解绑 VAO
    //游戏循环
    while (!glfwWindowShouldClose(window)) {
        //检查是否有事件发生
        glfwPollEvents();

        //重置颜色
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        //运行shaderProgram
        glUseProgram(shaderProgram);
        glBindVertexArray(VAOs[0]);
        //画出三角形
        glDrawArrays(GL_TRIANGLES, 0, 3);

        glUseProgram(shaderProgram2);
        glBindVertexArray(VAOs[1]);
        //画出三角形
        glDrawArrays(GL_TRIANGLES, 0, 3);
        glBindVertexArray(0);
        //交换缓存
        glfwSwapBuffers(window);

    }

    glDeleteVertexArrays(2, VAOs);
    glDeleteBuffers(2, VBOs);

    glfwTerminate();
    return 0;
}

void key_callback(GLFWwindow *window, int key, int scancode, int action, int mode) {
    if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
        glfwSetWindowShouldClose(window, GL_TRUE);
}

这是 learnopengl 里的习题