OpenGL创建一个带颜色的矩形

---

---

 Shader.h

#pragma once

#define GLEW_STATIC
#include  <GL\glew.h>
#include <GLFW/glfw3.h>

#include <string>
#include <fstream>
#include <sstream>
#include <iostream>

class Shader
{
public:
	Shader(const char* vertexPath, const char* fragmentPath);
	~Shader();
	unsigned int ID;
	void Shader::use();
	void Shader::setBool(const std::string &name, bool value) const;
	void Shader::setInt(const std::string &name, int value) const;
	void Shader::setFloat(const std::string &name, float value) const;

private:
	void Shader::checkCompileErrors(unsigned int shader, std::string type);
};

---

Shader.cpp

#include "Shader.h"


void Shader::use()
{
	glUseProgram(ID);
}
// utility uniform functions
// ------------------------------------------------------------------------
void Shader::setBool(const std::string &name, bool value) const
{
	glUniform1i(glGetUniformLocation(ID, name.c_str()), (int)value);
}
// ------------------------------------------------------------------------
void Shader::setInt(const std::string &name, int value) const
{
	glUniform1i(glGetUniformLocation(ID, name.c_str()), value);
}
// ------------------------------------------------------------------------
void Shader::setFloat(const std::string &name, float value) const
{
	glUniform1f(glGetUniformLocation(ID, name.c_str()), value);
}

void Shader::checkCompileErrors(unsigned int shader, std::string type)
{
	int success;
	char infoLog[1024];
	if (type != "PROGRAM")
	{
		glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
		if (!success)
		{
			glGetShaderInfoLog(shader, 1024, NULL, infoLog);
			std::cout << "ERROR::SHADER_COMPILATION_ERROR of type: " << type << "\n" << infoLog << "\n -- --------------------------------------------------- -- " << std::endl;
		}
	}
	else
	{
		glGetProgramiv(shader, GL_LINK_STATUS, &success);
		if (!success)
		{
			glGetProgramInfoLog(shader, 1024, NULL, infoLog);
			std::cout << "ERROR::PROGRAM_LINKING_ERROR of type: " << type << "\n" << infoLog << "\n -- --------------------------------------------------- -- " << std::endl;
		}
	}
}


Shader::Shader(const char* vertexPath, const char* fragmentPath)
{
	// 1. 从文件路径中获取顶点/片段着色器
	std::string vertexCode;
	std::string fragmentCode;
	std::ifstream vShaderFile;
	std::ifstream fShaderFile;
	// 保证ifstream对象可以抛出异常：
	vShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
	fShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
	try
	{
		// 打开文件
		vShaderFile.open(vertexPath);
		fShaderFile.open(fragmentPath);
		std::stringstream vShaderStream, fShaderStream;
		// 读取文件的缓冲内容到数据流中
		vShaderStream << vShaderFile.rdbuf();
		fShaderStream << fShaderFile.rdbuf();
		// 关闭文件处理器
		vShaderFile.close();
		fShaderFile.close();
		// 转换数据流到string
		vertexCode = vShaderStream.str();
		fragmentCode = fShaderStream.str();
	}
	catch (std::ifstream::failure e)
	{
		std::cout << "ERROR::SHADER::FILE_NOT_SUCCESFULLY_READ" << std::endl;
	}
	const char* vShaderCode = vertexCode.c_str();
	const char* fShaderCode = fragmentCode.c_str();

	unsigned int vertex, fragment;
	
	// vertex shader
	vertex = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertex, 1, &vShaderCode, NULL);
	glCompileShader(vertex);
	checkCompileErrors(vertex, "VERTEX");
	// fragment Shader
	fragment = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragment, 1, &fShaderCode, NULL);
	glCompileShader(fragment);
	checkCompileErrors(fragment, "FRAGMENT");
	// shader Program
	ID = glCreateProgram();
	glAttachShader(ID, vertex);
	glAttachShader(ID, fragment);
	glLinkProgram(ID);
	checkCompileErrors(ID, "PROGRAM");
	// delete the shaders as they're linked into our program now and no longer necessary
	glDeleteShader(vertex);
	glDeleteShader(fragment);
}






Shader::~Shader()
{
}

---

 main.cpp

#define GLEW_STATIC
#include  <GL\glew.h>
#include <GLFW/glfw3.h>

#include <iostream>

#include "Shader.h"
using namespace std;
//QQ技术交流群：386476712

//terminate	[ˈtɜ:mɪneɪt]  结束 终结
//hint [hɪnt] 提示 注意事项


void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
	cout << "width :  " << width << endl;
	glViewport(0, 0, width, height);
}

int main(){

	

	//glfw初始化
	//告诉glfw当前所用的OpenGL的版本号是3.3
	//告诉glfw当前使用核心模式，意味着我们只能使用OpenGL功能的一个子集（没有我们已不再需要的向后兼容特性）
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	//使用glfw创建一个窗口
	GLFWwindow* window = glfwCreateWindow(800, 600, "Hunk Xu  OpenGL", NULL, NULL);
	if (window == NULL)
	{
		std::cout << "Failed to create GLFW window" << std::endl;
		glfwTerminate();
		return -1;
	}
	//通知GLFW将window的上下文设置为当前线程的主上下文,设置主活动窗口
	glfwMakeContextCurrent(window);

    
	//glew初始化
	if (glewInit() != GLEW_OK){
		printf("glew init failed");
		glfwTerminate();
		return -1;
	}

	//告诉OpenGL视口(Viewport)大小
	//前两个参数为窗口左下角位置
	//后两个参数渲染窗口的宽和高（像素）
	glViewport(0, 0, 800, 600);
	//每当窗口调整大小时候，就调用这个函数
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

	float vertices[] = {
		0.5f, 0.5f, 0.0f,  // top right
		0.5f, -0.5f, 0.0f,  // bottom right
		-0.5f, -0.5f, 0.0f,  // bottom left
		-0.5f, 0.5f, 0.0f   // top left 
	};
	unsigned int indices[] = {  // note that we start from 0!
		0, 1, 3,  // first Triangle
		1, 2, 3   // second Triangle
	};
	unsigned int VBO, VAO, EBO;
	glGenVertexArrays(1, &VAO);
	glGenBuffers(1, &VBO);
	glGenBuffers(1, &EBO);

	glBindVertexArray(VAO);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);//第二个参数要设置成你想操作内存的标识，然后接下来的操作都是针对这一块内存进行的
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

	glVertexAttribPointer(4, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(4);


	//将顶点数据buffer和之前的绑定关系进行解绑 用于打破之前的顶点数据buffer的绑定关系
	//使OpenGL的顶点数据buffer绑定状态恢复到默认状态。
	glBindBuffer(GL_ARRAY_BUFFER, 0); 



	//将VAO绑定到默认的VAO处，一般用于打破之前的VAO绑定关系
	//使OpenGL的VAO绑定状态恢复到默认状态
	glBindVertexArray(0);


	Shader* myShader = new Shader("vertexSource.txt", "fragementSource.txt");
	//渲染循环
	while (!glfwWindowShouldClose(window)){

		myShader->use();
		glBindVertexArray(VAO); 
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0); //6表示6个顶点索引

		//双缓冲(Double Buffer)
		//前缓冲保存着最终输出的图像，它会在屏幕上显示；
		//而所有的的渲染指令都会在后缓冲上绘制。
		//当所有的渲染指令执行完毕后，我们交换(Swap)前缓冲和后缓冲，这样图像就立即呈显出来
		//不会出现图像闪烁的问题
		glfwSwapBuffers(window);  
		glfwPollEvents(); //轮询用户的输入(键盘移动，鼠标输入)
	}

	//终止
	glfwTerminate();
	return 0;
}

---

fragementSource.txt

#version 330 core
out vec4 FragColor;

in vec4 vertexColor; // 从顶点着色器传来的输入变量（名称相同、类型相同）

void main()
{
    FragColor = vertexColor;
}

---

vertexSource.txt

#version 330 core
layout (location = 4) in vec3 aPos; // 位置变量的属性位置值为0

out vec4 vertexColor; // 为片段着色器指定一个颜色输出

void main()
{
    gl_Position = vec4(aPos, 1.0); // 注意我们如何把一个vec3作为vec4的构造器的参数
    vertexColor = vec4(0, 0, 1.0, 1.0); // 把输出变量设置为暗红色
}

---

最后运行结果：

---

---

FR:海涛高软（hunk Xu）
QQ技术交流群：386476712