计算机图形学（2）：OpenGL画球体

配置OpenGL环境看上一篇文章

效果图：

在这里插入图片描述

main.cpp：

#include "Dependencies/glew/glew.h"
#include "Dependencies/GLFW/glfw3.h"

#include "Dependencies/glm/glm.hpp"
#include "Dependencies/glm/gtc/matrix_transform.hpp"

#include <iostream>
#include <fstream>
#include <vector>
#include <math.h>

GLint programID;

unsigned int VBO, VAO, EBO;

const unsigned int SCR_WIDTH = 1200;
const unsigned int SCR_HEIGHT = 1200;


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;

void get_OpenGL_info() {
	// OpenGL information
	const GLubyte* name = glGetString(GL_VENDOR);
	const GLubyte* renderer = glGetString(GL_RENDERER);
	const GLubyte* glversion = glGetString(GL_VERSION);
	std::cout << "OpenGL company: " << name << std::endl;
	std::cout << "Renderer name: " << renderer << std::endl;
	std::cout << "OpenGL version: " << glversion << std::endl;
}

bool checkStatus(
	GLuint objectID,
	PFNGLGETSHADERIVPROC objectPropertyGetterFunc,
	PFNGLGETSHADERINFOLOGPROC getInfoLogFunc,
	GLenum statusType)
{
	GLint status;
	objectPropertyGetterFunc(objectID, statusType, &status);
	if (status != GL_TRUE)
	{
		GLint infoLogLength;
		objectPropertyGetterFunc(objectID, GL_INFO_LOG_LENGTH, &infoLogLength);
		GLchar* buffer = new GLchar[infoLogLength];

		GLsizei bufferSize;
		getInfoLogFunc(objectID, infoLogLength, &bufferSize, buffer);
		std::cout << buffer << std::endl;

		delete[] buffer;
		return false;
	}
	return true;
}

bool checkShaderStatus(GLuint shaderID) {
	return checkStatus(shaderID, glGetShaderiv, glGetShaderInfoLog, GL_COMPILE_STATUS);
}

bool checkProgramStatus(GLuint programID) {
	return checkStatus(programID, glGetProgramiv, glGetProgramInfoLog, GL_LINK_STATUS);
}

std::string readShaderCode(const char* fileName) {
	std::ifstream meInput(fileName);
	if (!meInput.good()) {
		std::cout << "File failed to load ... " << fileName << std::endl;
		exit(1);
	}
	return std::string(
		std::istreambuf_iterator<char>(meInput),
		std::istreambuf_iterator<char>()
	);
}

void installShaders() {
	GLuint vertexShaderID = glCreateShader(GL_VERTEX_SHADER);
	GLuint fragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);

	const GLchar* adapter[1];
	//adapter[0] = vertexShaderCode;
	std::string temp = readShaderCode("VertexShaderCode.glsl");
	adapter[0] = temp.c_str();
	glShaderSource(vertexShaderID, 1, adapter, 0);
	//adapter[0] = fragmentShaderCode;
	temp = readShaderCode("FragmentShaderCode.glsl");
	adapter[0] = temp.c_str();
	glShaderSource(fragmentShaderID, 1, adapter, 0);

	glCompileShader(vertexShaderID);
	glCompileShader(fragmentShaderID);

	if (!checkShaderStatus(vertexShaderID) || !checkShaderStatus(fragmentShaderID))
		return;

	programID = glCreateProgram();
	glAttachShader(programID, vertexShaderID);
	glAttachShader(programID, fragmentShaderID);
	glLinkProgram(programID);

	if (!checkProgramStatus(programID))
		return;

	glDeleteShader(vertexShaderID);
	glDeleteShader(fragmentShaderID);

	glUseProgram(programID);

}

void sendDataToOpenGL() {
	// TODO:
	// create 2D objects and 3D objects and/or lines (points) here and bind to VAOs & VBOs

	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);
		}
	}

	glGenVertexArrays(1, &VAO);
	glGenBuffers(1, &VBO);
	glGenBuffers(1, &EBO);

	glBindVertexArray(VAO);	
	glBindBuffer(GL_ARRAY_BUFFER, VBO);	
	glBufferData(GL_ARRAY_BUFFER, sphereVertices.size() * sizeof(float), &sphereVertices[0], GL_STATIC_DRAW);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0); // because the vertex data is tightly packed we can also specify 0 as the vertex attribute's stride to let OpenGL figure it out
	glEnableVertexAttribArray(0);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sphereIndices.size() * sizeof(int), &sphereIndices[0], GL_STATIC_DRAW);
	


}

void paintGL(void) {
	// always run
	// TODO:
	// render your objects and control the transformation here
	glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	glm::mat4 projection = glm::mat4(1.0f);
	glm::mat4 model = glm::mat4(1.0f);
	glm::mat4 view = glm::mat4(1.0f);

	glUniformMatrix4fv(glGetUniformLocation(programID, "projection"), 1, GL_FALSE, &projection[0][0]);
	glUniformMatrix4fv(glGetUniformLocation(programID, "view"), 1, GL_FALSE, &view[0][0]);
	glUniformMatrix4fv(glGetUniformLocation(programID, "model"), 1, GL_FALSE, &model[0][0]);

	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);

	


}


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

void initializedGL(void) {
	// run only once
	// TODO:
	sendDataToOpenGL();
	installShaders();
	glEnable(GL_DEPTH_TEST);
}

int main(int argc, char* argv[]) {
	GLFWwindow* window;

	/* Initialize the glfw */
	if (!glfwInit()) {
		std::cout << "Failed to initialize GLFW" << std::endl;
		return -1;
	}
	/* glfw: configure; necessary for MAC */
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

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

	/* do not allow resizing */
	glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);

	/* Create a windowed mode window and its OpenGL context */
	window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "Assignment 1", NULL, NULL);
	if (!window) {
		std::cout << "Failed to create GLFW window" << std::endl;
		glfwTerminate();
		return -1;
	}

	/* Make the window's context current */
	glfwMakeContextCurrent(window);
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

	/* Initialize the glew */
	if (GLEW_OK != glewInit()) {
		std::cout << "Failed to initialize GLEW" << std::endl;
		return -1;
	}
	get_OpenGL_info();
	initializedGL();



	/* Loop until the user closes the window */
	while (!glfwWindowShouldClose(window)) {
		/* Render here */
		paintGL();

		/* Swap front and back buffers */
		glfwSwapBuffers(window);

		/* Poll for and process events */
		glfwPollEvents();
	}



	glfwTerminate();
	return 0;
}

顶点着色器：

#version 330 core
layout (location = 0) in vec3 aPos;

void main()
{
    gl_Position = vec4(aPos, 1.0);
}

片段着色器：

#version 330 core
out vec4 FragColor;

void main()
{
    FragColor = vec4(1.0,0.635,0.345,1.0);
}

想画的更圆可以通过增大全局变量Y_SEGMENTS和X_SEGMENTS

下面是100时的效果

在这里插入图片描述

要给球体上颜色的话，每次生成顶点时要压入三个颜色的比例值，同时在顶点着色器中加入颜色输入值，下面是修改部分：

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);

			//压入顶点坐标
			sphereVertices.push_back(xPos);
			sphereVertices.push_back(yPos);
			sphereVertices.push_back(zPos);
			//压入颜色
			sphereVertices.push_back(sin(xPos) / 2 + 0.5);
			sphereVertices.push_back(sin(yPos) / 2 + 0.5);
			sphereVertices.push_back(sin(zPos) / 2 + 0.5);
		}
	}

同时将颜色传入顶点着色器中，注意偏移值要改成6

glBindVertexArray(VAO);	
	glBindBuffer(GL_ARRAY_BUFFER, VBO);	
	glBufferData(GL_ARRAY_BUFFER, sphereVertices.size() * sizeof(float), &sphereVertices[0], GL_STATIC_DRAW);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0); 
	glEnableVertexAttribArray(0);
	//新增两行
	glEnableVertexAttribArray(1);
	glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (char*)(3 * sizeof(float))); 
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sphereIndices.size() * sizeof(int), &sphereIndices[0], GL_STATIC_DRAW);

绘线模式去除

glBindVertexArray(VAO);
glDrawElements(GL_TRIANGLES, X_SEGMENTS * Y_SEGMENTS * 6, GL_UNSIGNED_INT, 0);

顶点着色器：

#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aColor;

out vec3 ourColor;

void main()
{
    gl_Position = vec4(aPos, 1.0);
    ourColor = aColor ;
}

片段着色器：

#version 330 core

out vec4 FragColor;

in vec3 ourColor;


void main()
{
    FragColor = vec4(ourColor,1.0);
}

效果图：

在这里插入图片描述

工程文件

原文链接：https://blog.csdn.net/qq_51684393/article/details/129801437

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