OpenGL使用纯VBO方式渲染出三角形，非VAO

OpenGL使用纯VBO方式渲染出三角形，要设置兼容格式GLFW_OPENGL_COMPAT_PROFILE。

    // 必须使用VAO渲染
    //glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    // 渲染出纯VBO三角形
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_COMPAT_PROFILE);

 

#include <glad/glad.h>
#include <GLFW/glfw3.h>

#include <iostream>

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);

// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

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

const char* fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
"   FragColor = vec4(1.0f, 0.0f, 0.0f, 1.0f);\n"
"}\0";

int main()
{
    // glfw: initialize and configure
    // ------------------------------
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);

    // 必须使用VAO渲染
    //glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    // 渲染出纯VBO三角形
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_COMPAT_PROFILE);

#ifdef __APPLE__
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif

    // glfw window creation
    // --------------------
    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    // glad: load all OpenGL function pointers
    // ---------------------------------------
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }  

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

    // 生成一个VBO对象
    unsigned int VBO;
    glGenBuffers(1, &VBO);

    // 生成一个VAO
    //unsigned int VAO;
    //glGenVertexArrays(1, &VAO);
    //glBindVertexArray(VAO);

    // 绑定到数组缓冲
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    // 复制顶点数据到缓冲内存
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    printf("glBufferData sizeof(vertices)=%d\n", sizeof(vertices));
    // sizeof(vertices)=36
    // 设置顶点属性指针，并启用
    //layout(location = 0 aPosition
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
    //location = 0
    glEnableVertexAttribArray(0); //顶点坐标
    // 解绑
    // note that this is allowed, the call to glVertexAttribPointer registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
    glBindBuffer(GL_ARRAY_BUFFER, 0);

    /*三角形的位置数据不会改变，每次渲染调用时都保持原样，所以它的使用类型最好是GL_STATIC_DRAW。
    如果，比如说一个缓冲中的数据将频繁被改变，
    那么使用的类型就是GL_DYNAMIC_DRAW或GL_STREAM_DRAW，
    这样就能确保显卡把数据放在能够高速写入的内存部分。*/

    // 创建顶点着色器，
    unsigned int vertexShader;
    vertexShader = glCreateShader(GL_VERTEX_SHADER);
    // 附加上着色器源代码
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    // 编译着色器
    glCompileShader(vertexShader);

    // 检测是否编译成功
    int success = 0;
    char infoLog[512] = { 0 };
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        glGetShaderInfoLog(vertexShader, sizeof(infoLog), NULL, infoLog);
        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
    }
    else
    {
        std::cout << "SHADER::VERTEX::COMPILATION SUCCESS!";
    }

    // 创建片段着色器
    unsigned int fragmentShader;
    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    // 附加上片段着色器源代码
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    // 编译
    glCompileShader(fragmentShader);

    // 判断编译结果
    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        glGetShaderInfoLog(fragmentShader, sizeof(infoLog), NULL, infoLog);
        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
    }
    else
    {
        std::cout << "SHADER::FRAGMENT::COMPILATION SUCCESS!" << std::endl;
    }

    // 创建着色器程序
    unsigned int shaderProgram;
    shaderProgram = glCreateProgram();
    // 链接之前编译的着色器
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);

    // 判断着色器程序链接结果
    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::PROGRAM::COMPILATION_FAILED\n" << infoLog << std::endl;
    }
    else
    {
        std::cout << "SHADER::LinkProgram SUCCESS!" << std::endl;
    }

    // 删除之前链接过的对象
    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);

    // You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
    // VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
    //glBindVertexArray(0);

    // render loop
    // -----------
    while (!glfwWindowShouldClose(window))
    {
        // input
        // -----
        processInput(window);

        // render
        // ------
        glClearColor(0.1f, 0.3f, 0.2f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        // 激活程序对象
        glUseProgram(shaderProgram);

        //glBindVertexArray(VAO);
        //glBindVertexArray(VAO);
        //glBindBuffer(GL_ARRAY_BUFFER, VBO);     
        glDrawArrays(GL_TRIANGLES, 0, 3);

        //glDrawElements(GL_TRIANGLES, 1, GL_UNSIGNED_SHORT, 0);

        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        // -------------------------------------------------------------------------------
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glDeleteBuffers(1, &VBO);
    glDeleteProgram(shaderProgram);

    // glfw: terminate, clearing all previously allocated GLFW resources.
    // ------------------------------------------------------------------
    glfwTerminate();
    return 0;
}

// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow *window)
{
    if(glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);
}

// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    // make sure the viewport matches the new window dimensions; note that width and 
    // height will be significantly larger than specified on retina displays.
    //glViewport(0, 0, width, height);
    glViewport(0, 0, 100, 100);
}

标签：VAO,OpenGL,int,VBO,window,GLFW,GL
来源： https://blog.csdn.net/a2831942318/article/details/122385250