/***
* 例程 绘制球体 (MAKE后运行时可删除ALL_BUILD,也可以将Task-sphere设为默认启动工程)
* 步骤:
* 1-初始化: GLFW窗口,GLAD。
* 2-计算球体顶点:通过数学方法计算球体的每个顶点坐标
* 2-数据处理: 通过球体顶点坐标构造三角形网格,生成并绑定VAO&VBO&EBO(准备在GPU中进行处理),设置顶点属性指针(本质上就是告诉OpenGL如何处理数据)。
* 3-着色器: 给出顶点和片段着色器,然后链接为着色器程序,渲染时使用着色器程序。
* 4-渲染: 使用画线模式画圆,开启面剔除,剔除背面,使用线框模式画球
* 5-结束: 清空缓冲,交换缓冲区检查触发事件后释放资源
*/
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include "shader.h"
#include <iostream>
#include <math.h>
#include <vector>
const unsigned int screen_width = 780;
const unsigned int screen_height = 780;
const GLfloat PI = 3.14159265358979323846f;
// 将球横纵划分成50X50的网格
const int Y_SEGMENTS = 50;
const int X_SEGMENTS = 50;
int main()
{
// 初始化GLFW
glfwInit(); // 初始化GLFW
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); // OpenGL版本为3.3,主次版本号均设为3
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); // 使用核心模式(无需向后兼容性)
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // 如果使用的是Mac OS X系统,需加上这行
glfwWindowHint(GLFW_RESIZABLE, false); // 不可改变窗口大小
// 创建窗口(宽、高、窗口名称)
auto window = glfwCreateWindow(screen_width, screen_height, "Sphere", nullptr, nullptr);
if (window == nullptr)
{ // 如果窗口创建失败,输出Failed to Create OpenGL Context
std::cout << "Failed to Create OpenGL Context" << std::endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window); // 将窗口的上下文设置为当前线程的主上下文
// 初始化GLAD,加载OpenGL函数指针地址的函数
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
// 指定当前视口尺寸(前两个参数为左下角位置,后两个参数是渲染窗口宽、高)
glViewport(0, 0, screen_width, screen_height);
Shader shader("res/shader/task3.vs", "res/shader/task3.fs"); // 加载着色器
std::vector<float> sphereVertices;
std::vector<int> sphereIndices;
// 生成球的顶点
for (int y = 0; y <= Y_SEGMENTS; y++)
{
for (int x = 0; x <= X_SEGMENTS; x++)
{
float xSegment = (float)x / (float)X_SEGMENTS;
float ySegment = (float)y / (float)Y_SEGMENTS;
float xPos = std::cos(xSegment * 2.0f * PI) * std::sin(ySegment * PI);
float yPos = std::cos(ySegment * PI);
float zPos = std::sin(xSegment * 2.0f * PI) * std::sin(ySegment * PI);
sphereVertices.push_back(xPos);
sphereVertices.push_back(yPos);
sphereVertices.push_back(zPos);
}
}
// 根据球面上每一点的坐标,去构造一个三角形顶点数组
for (int i = 0; i < Y_SEGMENTS; i++)
{
for (int j = 0; j < X_SEGMENTS; j++)
{
sphereIndices.push_back(i * (X_SEGMENTS + 1) + j);
sphereIndices.push_back((i + 1) * (X_SEGMENTS + 1) + j);
sphereIndices.push_back((i + 1) * (X_SEGMENTS + 1) + j + 1);
sphereIndices.push_back(i * (X_SEGMENTS + 1) + j);
sphereIndices.push_back((i + 1) * (X_SEGMENTS + 1) + j + 1);
sphereIndices.push_back(i * (X_SEGMENTS + 1) + j + 1);
}
}
// 球
unsigned int VBO, VAO;
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
// 生成并绑定球体的VAO和VBO
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
// 将顶点数据绑定至当前默认的缓冲中
glBufferData(GL_ARRAY_BUFFER, sphereVertices.size() * sizeof(float), &sphereVertices[0], GL_STATIC_DRAW);
GLuint element_buffer_object; // EBO
glGenBuffers(1, &element_buffer_object);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, element_buffer_object);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sphereIndices.size() * sizeof(int), &sphereIndices[0], GL_STATIC_DRAW);
// 设置顶点属性指针
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
glEnableVertexAttribArray(0);
// 解绑VAO和VBO
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
// 渲染循环
while (!glfwWindowShouldClose(window))
{
// 清空颜色缓冲
glClearColor(0.0f, 0.34f, 0.57f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
shader.Use();
// 绘制球
// 开启面剔除(只需要展示一个面,否则会有重合)
glEnable(GL_CULL_FACE);
glCullFace(GL_BACK);
glBindVertexArray(VAO);
// 使用线框模式绘制
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glDrawElements(GL_TRIANGLES, X_SEGMENTS * Y_SEGMENTS * 6, GL_UNSIGNED_INT, 0);
// 点阵模式绘制
// glPointSize(5);
// glDrawElements(GL_POINTS, X_SEGMENTS*Y_SEGMENTS*6, GL_UNSIGNED_INT, 0);
// 交换缓冲并且检查是否有触发事件(比如键盘输入、鼠标移动等)
glfwSwapBuffers(window);
glfwPollEvents();
}
// 删除VAO和VBO,EBO
glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(1, &VBO);
glDeleteBuffers(1, &element_buffer_object);
// 清理所有的资源并正确退出程序
glfwTerminate();
return 0;
}