OpenGL 矩阵绘画

// OpenGLDemo.cpp: 定义控制台应用程序的入口点。

#include "stdafx.h"
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <fstream>
#include <string>
#include <cstring>

using namespace std;

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow* window);
char* readTheFile(string strSource);

const char* vertexShaderSource = readTheFile("vertexShaderSource.vert");
const char* fragmentShaderSource = readTheFile("fragmentShaderSource.frag");

class MyTriangle {
public:
    float vertices[18] = {
        .5f,.5f,.0f,//右上
        -.5f,.5f,.0f,//左上
        .5f,-.5f,.0f,//右下
        -.5f,-.5f,.0f//左下
    };
    unsigned int indices[6] = {
        0,2,1,
        1,3,2
    };
    //生成顶点缓冲对象 ID:VBO
    unsigned int VBO;
    //生成顶点数组对象 ID:VAO
    unsigned int VAO;
    //生成引索对象
    unsigned int EBO;
    //储存 顶点着色器
    unsigned int vertexShader;
    //储存 片段着色器
    unsigned int fragmentShader;
    //存储 着色器程序
    unsigned int shaderProgram;

    void drawMyGraph(){
        vertexShaderInit();
        FragmentShaderInit();
        shaderProgramLinker();
        vertexInput();
    }
private:
    void vertexInput() {
        glGenBuffers(1, &VBO);
        glGenVertexArrays(1, &VAO);
        glGenBuffers(1, &EBO);
        // 1. 绑定VAO , VBO
        glBindVertexArray(VAO);

        // 2. 复制顶点数组到缓冲中供OpenGL使用
        //将缓冲对象 绑定到GL_ARRAY_BUFFER目标
        glBindBuffer(GL_ARRAY_BUFFER, VBO);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
        //定义顶点数据复制到缓冲内存
        glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,GL_STATIC_DRAW);
        // 3. 设置顶点属性指针
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
        glEnableVertexAttribArray(0);
    }

    void vertexShaderInit() {
        //创建一个顶点着色器对象
        vertexShader = glCreateShader(GL_VERTEX_SHADER);
        //着色器源码附着到着色器对象上
        glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
        //编译着色器对象
        glCompileShader(vertexShader);
        
        //检测着色编译是否成功
        int success;
        char infoLog[22];
        glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
        if (!success) {
            glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
            std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
        }
    }

    void FragmentShaderInit() {
        fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(fragmentShader, 1, &fragmentShaderSource,NULL);
        glCompileShader(fragmentShader);
        //检测着色编译是否成功
        int success;
        char infoLog[22];
        glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
        if (!success) {
            glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
            std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
        }
    }

    void shaderProgramLinker() {
        //创建着色器程序对象
        shaderProgram = glCreateProgram();
        //附加着色器到着色器程序
        glAttachShader(shaderProgram, vertexShader);
        glAttachShader(shaderProgram, fragmentShader);
        glLinkProgram(shaderProgram);
        int success;
        char infoLog[22];
        glGetProgramiv(shaderProgram, GL_LINK_STATUS,&success);
        if (!success) {
            glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
            std::cout << "ERROR::SHADER::LINKE_PROGRAM::COMPILATION_FAILED\n" << infoLog << std::endl;
        }
        glDeleteShader(vertexShader);
        glDeleteShader(fragmentShader);
    }

};

int main()
{
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR,3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR,3);
    glfwWindowHint(GLFW_OPENGL_PROFILE,GLFW_OPENGL_CORE_PROFILE);
    GLFWwindow* window = glfwCreateWindow(800, 600, "Oh!I see you!", NULL, NULL);
    if (window == NULL) {
        std::cout << "Failed to create the windows" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }

    MyTriangle myTriangle;
    myTriangle.drawMyGraph();
    //启用线段模式
    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
    while (!glfwWindowShouldClose(window)) {

        //输入处理
        processInput(window);

        //渲染指令
        glClearColor(0.2f,0.3f,0.3f,1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        // 4. 当我们渲染一个物体时要使用着色器程序
        glUseProgram(myTriangle.shaderProgram);
        glBindVertexArray(myTriangle.VAO);
        // 3. 绘制物体
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
        glBindVertexArray(0);

        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glDeleteVertexArrays(1, &myTriangle.VAO);
    glDeleteBuffers(1, &myTriangle.VBO);
    glfwTerminate();
    return 0;
}

void framebuffer_size_callback(GLFWwindow* windows, int width, int height) {
    glViewport(0, 0, width, height);
}

void processInput(GLFWwindow* window) {
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS) {
        glfwSetWindowShouldClose(window, true);
    }
}

//.frag .vert文件读取
char* readTheFile(string strSource) {
    std::ifstream myfile(strSource);
    std::string str((std::istreambuf_iterator<char>(myfile)),
        std::istreambuf_iterator<char>());
    //str数组长度一定要 +1,
    /*原因: https://blog.csdn.net/ShiQW5696/article/details/80676290 */
    int len = str.length();
    char* result = new char[len];
    strcpy_s(result, len + 1, str.c_str());
    return result;
}