如何绘制五角星见：http://t.csdn.cn/5rMA1，本文国旗由五个五角星组成

使用OpenGL通过VAO数组、VBO数组和EBO数组绘制五星红旗

#include<iostream>
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include<cmath>#define pi 3.14159265const char* fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
"   FragColor = vec4(255.0f, 222.0f, 0.0f, 1.0f);\n"
"}\n\0";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";void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{glViewport(0, 0, width, height);
}void processInput(GLFWwindow* window)
{if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)glfwSetWindowShouldClose(window, true);
}float ang2rad(float ang) {return (ang * pi) / 180;
}float findBiggerRadius(float smallR) {float a, b, c, x1, x2, d;float num1 = sin(ang2rad(36)) / sin(ang2rad(126));a = (1 - (pow(num1, 2)));b = (2 * num1 * smallR * cos(ang2rad(126)));c = -(smallR * smallR);//scanf("%f %f %f",&a,&b,&c);if (a != 0){d = sqrt(b * b - 4 * a * c);x1 = (-b + d) / (2 * a);x2 = (-b - d) / (2 * a);if (x1 < x2)return x2;elsereturn x1;}return -1;
}int main()
{glfwInit();glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);//将主版本号(Major)和次版本号(Minor)都设为3glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);//告诉GLFW我们使用的是核心模式(Core-profile)GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);if (window == NULL){std::cout << "Failed to create GLFW window" << std::endl;glfwTerminate();return -1;}glfwMakeContextCurrent(window);if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))//我们给GLAD传入了用来加载系统相关的OpenGL函数指针地址的函数。GLFW给我们的是glfwGetProcAddress，它根据我们编译的系统定义了正确的函数。{std::cout << "Failed to initialize GLAD" << std::endl;return -1;}glViewport(0, 0, 500, 500);glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);unsigned int vertexShader;vertexShader = glCreateShader(GL_VERTEX_SHADER);glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);glCompileShader(vertexShader);unsigned int fragmentShader;fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);glCompileShader(fragmentShader);unsigned int shaderProgram;shaderProgram = glCreateProgram();glAttachShader(shaderProgram, vertexShader);glAttachShader(shaderProgram, fragmentShader);glLinkProgram(shaderProgram);//glUseProgram(shaderProgram);glDeleteShader(vertexShader);glDeleteShader(fragmentShader);//Vertex1float v_center1x = -0.5f;float v_center1y = 0.5f;float radius_small = 0.1f;float radius_big = findBiggerRadius(radius_small);float v[35];float degree = 54.0f;int i = 0;while (i < 15) {v[i++] = v_center1x + radius_small * cos(ang2rad(degree));v[i++] = v_center1y + radius_small * sin(ang2rad(degree));v[i++] = 1.0f;degree += 72.0f;}degree = 18.0f;while (i < 30) {v[i++] = v_center1x + radius_big * cos(ang2rad(degree));v[i++] = v_center1y + radius_big * sin(ang2rad(degree));v[i++] = 1.0f;degree += 72.0f;}v[i++] = v_center1x;v[i++] = v_center1y;v[i++] = 1.0f;//Vertex2float v1[35];v_center1x = -0.1f;v_center1y = 0.80f;radius_small = 0.05f;radius_big = findBiggerRadius(radius_small);degree = 94.0f;i = 0;while (i < 15) {v1[i++] = v_center1x + radius_small * cos(ang2rad(degree));v1[i++] = v_center1y + radius_small * sin(ang2rad(degree));v1[i++] = 1.0f;degree += 72.0f;}degree = 58.0f;while (i < 30) {v1[i++] = v_center1x + radius_big * cos(ang2rad(degree));v1[i++] = v_center1y + radius_big * sin(ang2rad(degree));v1[i++] = 1.0f;degree += 72.0f;}v1[i++] = v_center1x;v1[i++] = v_center1y;v1[i++] = 1.0f;//Vertex3float v2[35];v_center1x = 0.1f;v_center1y = 0.50f;radius_small = 0.05f;radius_big = findBiggerRadius(radius_small);degree = 74.0f;i = 0;while (i < 15) {v2[i++] = v_center1x + radius_small * cos(ang2rad(degree));v2[i++] = v_center1y + radius_small * sin(ang2rad(degree));v2[i++] = 1.0f;degree += 72.0f;}degree = 38.0f;while (i < 30) {v2[i++] = v_center1x + radius_big * cos(ang2rad(degree));v2[i++] = v_center1y + radius_big * sin(ang2rad(degree));v2[i++] = 1.0f;degree += 72.0f;}v2[i++] = v_center1x;v2[i++] = v_center1y;v2[i++] = 1.0f;//Vertex4float v3[35];v_center1x = 0.05f;v_center1y = 0.15f;radius_small = 0.05f;radius_big = findBiggerRadius(radius_small);degree = 54.0f;i = 0;while (i < 15) {v3[i++] = v_center1x + radius_small * cos(ang2rad(degree));v3[i++] = v_center1y + radius_small * sin(ang2rad(degree));v3[i++] = 1.0f;degree += 72.0f;}degree = 18.0f;while (i < 30) {v3[i++] = v_center1x + radius_big * cos(ang2rad(degree));v3[i++] = v_center1y + radius_big * sin(ang2rad(degree));v3[i++] = 1.0f;degree += 72.0f;}v3[i++] = v_center1x;v3[i++] = v_center1y;v3[i++] = 1.0f;//Vertex5float v4[35];v_center1x = -0.2f;v_center1y = -0.1f;radius_small = 0.05f;radius_big = findBiggerRadius(radius_small);degree = 34.0f;i = 0;while (i < 15) {v4[i++] = v_center1x + radius_small * cos(ang2rad(degree));v4[i++] = v_center1y + radius_small * sin(ang2rad(degree));v4[i++] = 1.0f;degree += 72.0f;}degree = -2.0f;while (i < 30) {v4[i++] = v_center1x + radius_big * cos(ang2rad(degree));v4[i++] = v_center1y + radius_big * sin(ang2rad(degree));v4[i++] = 1.0f;degree += 72.0f;}v4[i++] = v_center1x;v4[i++] = v_center1y;v4[i++] = 1.0f;/*unsigned int indices[] = {// 注意索引从0开始!// 此例的索引(0,1,2,3)就是顶点数组vertices的下标，// 这样可以由下标代表顶点组合成矩形0, 1, 3, // 第一个三角形1, 2, 3  // 第二个三角形};*/unsigned int indices[] = {// 注意索引从0开始! // 此例的索引(0,1,2,3)就是顶点数组vertices的下标，// 这样可以由下标代表顶点组合成矩形0, 6, 10,6, 1, 10,1, 7, 10,2, 7, 10,2, 8, 10,3, 8, 10,3, 9, 10,4, 9, 10,4, 5, 10,0, 5, 10};glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);glEnableVertexAttribArray(0);unsigned int VBO[5], VAO[5], EBO[5];glGenVertexArrays(6, VAO);glGenBuffers(6, VBO);glGenBuffers(6, EBO);//BIND BIGSTARglBindVertexArray(VAO[0]);glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);glBufferData(GL_ARRAY_BUFFER, sizeof(v), v, GL_STATIC_DRAW);glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[0]);glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);glVertexAttribPointer(0, 3, GL_FLOAT, GL_TRUE, 3 * sizeof(float), (void*)0);glEnableVertexAttribArray(0);glBindBuffer(GL_ARRAY_BUFFER, 0);glBindVertexArray(0);//BIND SMALLSTAR1glBindVertexArray(VAO[1]);glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);glBufferData(GL_ARRAY_BUFFER, sizeof(v1), v1, GL_STATIC_DRAW);glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[1]);glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);glVertexAttribPointer(0, 3, GL_FLOAT, GL_TRUE, 3 * sizeof(float), (void*)0);glEnableVertexAttribArray(0);glBindBuffer(GL_ARRAY_BUFFER, 0);glBindVertexArray(0);//BIND SMALLSTAR2glBindVertexArray(VAO[2]);glBindBuffer(GL_ARRAY_BUFFER, VBO[2]);glBufferData(GL_ARRAY_BUFFER, sizeof(v2), v2, GL_STATIC_DRAW);glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[2]);glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);glVertexAttribPointer(0, 3, GL_FLOAT, GL_TRUE, 3 * sizeof(float), (void*)0);glEnableVertexAttribArray(0);glBindBuffer(GL_ARRAY_BUFFER, 0);glBindVertexArray(0);//BIND SMALLSTAR3glBindVertexArray(VAO[3]);glBindBuffer(GL_ARRAY_BUFFER, VBO[3]);glBufferData(GL_ARRAY_BUFFER, sizeof(v3), v3, GL_STATIC_DRAW);glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[3]);glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);glVertexAttribPointer(0, 3, GL_FLOAT, GL_TRUE, 3 * sizeof(float), (void*)0);glEnableVertexAttribArray(0);glBindBuffer(GL_ARRAY_BUFFER, 0);glBindVertexArray(0);//BIND SMALLSTAR3glBindVertexArray(VAO[4]);glBindBuffer(GL_ARRAY_BUFFER, VBO[4]);glBufferData(GL_ARRAY_BUFFER, sizeof(v4), v4, GL_STATIC_DRAW);glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[4]);glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);glVertexAttribPointer(0, 3, GL_FLOAT, GL_TRUE, 3 * sizeof(float), (void*)0);glEnableVertexAttribArray(0);glBindBuffer(GL_ARRAY_BUFFER, 0);glBindVertexArray(0);while (!glfwWindowShouldClose(window))//我们需要在程序中添加一个while循环，我们可以把它称之为渲染循环(Render Loop)，它能在我们让GLFW退出前一直保持运行{// 输入processInput(window);//渲染指令QAQ//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);glClearColor(1.0f, 0.0f, 0.0f, 1.0f);glClear(GL_COLOR_BUFFER_BIT);glUseProgram(shaderProgram);glBindVertexArray(VAO[0]);glDrawElements(GL_TRIANGLES, 30, GL_UNSIGNED_INT, 0);glUseProgram(shaderProgram);glBindVertexArray(VAO[1]);glDrawElements(GL_TRIANGLES, 30, GL_UNSIGNED_INT, 0);glBindVertexArray(VAO[2]);glDrawElements(GL_TRIANGLES, 30, GL_UNSIGNED_INT, 0);glBindVertexArray(VAO[3]);glDrawElements(GL_TRIANGLES, 30, GL_UNSIGNED_INT, 0);glBindVertexArray(VAO[4]);glDrawElements(GL_TRIANGLES, 30, GL_UNSIGNED_INT, 0);//检查并调用事件，交换缓冲glfwSwapBuffers(window);glfwPollEvents();}glfwTerminate();return 0;
}

实现效果

参考1：LearnOpenGL CN：https://learnopengl-cn.github.io/01%20Getting%20started/04%20Hello%20Triangle/
参考2：沙拉酱609 opengl之如何在一个窗口中绘制多个角色/物体：https://blog.csdn.net/qq_45543503/article/details/120671763

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【OpenGL】VAO数组实现一个OpenGL程序绘制多个图形：绘制五星红旗

使用OpenGL通过VAO数组、VBO数组和EBO数组绘制五星红旗

实现效果

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