C++ OpenGL绘制球

代码骑士 2022-09-27 我要评论

1、封装Shader

（1）为什么要封装Shader

封装后，在应对存在对个着色器程序的渲染流程时，可以更方便使用不同的着色器程序，同时也可以降低代码冗余。

（2）如何使用

如下，传入参数分别为顶点着色器和片元着色器的路径，在封装了Shader类之后，我们就可以通过一行代码去创建一个新的着色器对象：

Shader shader("res/shader/task3.vs","res/shader/task3.fs");

假如我们在绘制时需要切换到某个着色器并使用它，我们仅需要一行代码：

shader.Use();

假如我们需要向着色器传入一种类型的值，我们也仅需要一行代码去解决它（name是着色器中的名称，value为你希望设置的值）：

SetFloat(string &name,float value)

2、绘制球模型

（1）球面顶点遍历

//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(ySement*PI);
            float yPos = std::cos(ySegment*PI);
            float zPos = std::sin(xSegment*2.0f*PI)*std::sin(ySement*PI);
            
            sphereVertices.push_back(x_Pos);
            sphereVertices.push_back(y_Pos);
            sphereVertices.push_back(z_Pos);
        }
}

（2）构造三角形图元

//根据球面上每一点的坐标，去构造一个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);
    }
 }

（3）开启线框模式

glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);//使用线框模式绘制

（4）开启面剔除

//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);

（5）最后

项目工程文件结构：

shader.h

/***
* 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);
		}
	}
 
	// 生成球的Indices
	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;
}

shader.cpp

#include "Shader.h"
#include "fstream"
#include "sstream"
#include "iostream"
 
Shader::Shader(const GLchar* vertex_shader_path, const GLchar* fragment_shader_path)
{
	std::string vertex_shader_code;
	std::string fragment_shader_code;
	if (GetShaderFromFile(vertex_shader_path, fragment_shader_path, &vertex_shader_code, &fragment_shader_code))
	{
		return;
	}
	if (LinkShader(vertex_shader_code.c_str(), fragment_shader_code.c_str()))
	{
		return;
	}
}
 
Shader::~Shader()
{
 
}
 
void Shader::Use()
{
	glUseProgram(ID);
}
 
void Shader::SetBool(const std::string &name, bool value) const
{
	SetInt(name, (int)value);
}
 
void Shader::SetInt(const std::string &name, int value) const
{
	glUniform1i(GetUniform(name), value);
}
 
void Shader::SetFloat(const std::string &name, float value) const
{
	glUniform1f(GetUniform(name), value);
}
 
void Shader::SetVec2(const std::string &name, float x, float y) const
{
	glUniform2f(GetUniform(name), x, y);
}
 
void Shader::SetVec2(const std::string &name, const glm::vec2 &value) const
{
	SetVec2(name, value.x, value.y);
}
 
void Shader::SetVec3(const std::string &name, float x, float y, float z) const
{
	glUniform3f(GetUniform(name), x, y, z);
}
 
void Shader::SetVec3(const std::string &name, const glm::vec3 &value) const
{
	SetVec3(name, value.x, value.y, value.z);
}
 
void Shader::SetVec4(const std::string &name, float x, float y, float z, float w) const
{
	glUniform4f(GetUniform(name), x, y, z, w);
}
 
void Shader::SetVec4(const std::string &name, const glm::vec4 &value) const
{
	SetVec4(name, value.x, value.y, value.z, value.w);
}
 
void Shader::SetMat2(const std::string &name, const glm::mat2 &value) const
{
	glUniformMatrix2fv(GetUniform(name), 1, GL_FALSE, &value[0][0]);
}
 
void Shader::SetMat3(const std::string &name, const glm::mat3 &value) const
{
	glUniformMatrix3fv(GetUniform(name), 1, GL_FALSE, &value[0][0]);
}
 
void Shader::SetMat4(const std::string &name, const glm::mat4 &value) const
{
	glUniformMatrix4fv(GetUniform(name), 1, GL_FALSE, &value[0][0]);
}
 
int Shader::GetShaderFromFile(const GLchar* vertex_shader_path, const GLchar* fragment_shader_path, std::string *vertex_shader_code, std::string *fragment_shader_code)
{
	std::ifstream vertex_shader_file;
	std::ifstream fragment_shader_file;
	vertex_shader_file.exceptions(std::ifstream::badbit | std::ifstream::failbit);
	fragment_shader_file.exceptions(std::ifstream::badbit | std::ifstream::failbit);
	try
	{
		vertex_shader_file.open(vertex_shader_path);
		fragment_shader_file.open(fragment_shader_path);
		std::stringstream vertex_shader_stream, fragment_shader_stream;
		vertex_shader_stream << vertex_shader_file.rdbuf();
		fragment_shader_stream << fragment_shader_file.rdbuf();
		vertex_shader_file.close();
		fragment_shader_file.close();
		*vertex_shader_code = vertex_shader_stream.str();
		*fragment_shader_code = fragment_shader_stream.str();
	}
	catch (std::ifstream::failure e)
	{
		std::cout << "Load Shader File Error!" << std::endl;
		return -1;
	}
	return 0;
}
 
int Shader::LinkShader(const char* vertex_shader_code, const char* fragment_shader_code)
{
	int vertex_shader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertex_shader, 1, &vertex_shader_code, NULL);
	glCompileShader(vertex_shader);
	CheckCompileErrors(vertex_shader, "VERTEX");
 
	int fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragment_shader, 1, &fragment_shader_code, NULL);
	glCompileShader(fragment_shader);
	CheckCompileErrors(fragment_shader, "FRAGMENT");
 
	this->ID = glCreateProgram();
	glAttachShader(ID, vertex_shader);
	glAttachShader(ID, fragment_shader);
	glLinkProgram(ID);
	CheckCompileErrors(ID, "PROGRAM");
 
	glDeleteShader(vertex_shader);
	glDeleteShader(fragment_shader);
	return 0;
}
 
int Shader::GetUniform(const std::string &name) const
{
	int position = glGetUniformLocation(ID, name.c_str());
	if (position == -1)
	{
		std::cout << "uniform " << name << " set failed!" << std::endl;
	}
	return position;
}
 
void Shader::CheckCompileErrors(GLuint shader, std::string type)
{
	GLint success;
	GLchar infoLog[512];
	if (type == "PROGRAM")
	{
		glGetProgramiv(shader, GL_LINK_STATUS, &success);
		if (!success)
		{
			glGetProgramInfoLog(shader, 512, NULL, infoLog);
			std::cout << "ERROR::PROGRAM_LINKING_ERROR!\n" << infoLog << std::endl;
		}
	}
	else
	{
		glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
		if (!success)
		{
			glGetShaderInfoLog(shader, 512, NULL, infoLog);
			std::cout << "ERROR::SHADER::" << type << "::COMPILATION_FAILED\n" << infoLog << std::endl;
		}
	}
}

main.cpp

/***
* 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);
		}
	}
 
	// 生成球的Indices
	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;
}

输出结果：