main.cpp

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include<iostream>
#include<fstream>
#include<sstream>
#include<string>

unsigned int shaderProgram = 0;
unsigned int VBO = 0;
unsigned int VAO = 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);
	}
}

void initShader(const char* _vertexPath, const char* _fragPath)
{
	shaderProgram = 0;
	std::string  _vertexCode("");
	std::string  _fragCode("");

	std::ifstream   _vShaderFile;
	std::ifstream   _fShaderFile;

	//增加try catch的扩展功能
	_vShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
	_fShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);

	try
	{
		_vShaderFile.open(_vertexPath);
		_fShaderFile.open(_fragPath);

		std::stringstream   _vShaderStream, _fShaderStream;
		_vShaderStream << _vShaderFile.rdbuf();
		_fShaderStream << _fShaderFile.rdbuf();

		_vShaderFile.close();
		_fShaderFile.close();

		_vertexCode = _vShaderStream.str();
		_fragCode = _fShaderStream.str();
	}
	catch (std::ifstream::failure e)
	{
		std::string  errStr = "ffShader constructor fail to read filePath";
		std::cout << errStr << std::endl;
		return;
	}

	const char* _vShaderStr = _vertexCode.c_str();
	const char* _fShaderStr = _fragCode.c_str();

	unsigned int    _vertexID = 0, _fragID = 0;
	char    _infoLog[512];
	int     _successFlag;

	//创建顶点shader
	_vertexID = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(_vertexID, 1, &_vShaderStr, NULL);
	glCompileShader(_vertexID);

	glGetShaderiv(_vertexID, GL_COMPILE_STATUS, &_successFlag);
	if (!_successFlag)
	{
		glGetShaderInfoLog(_vertexID, 512, NULL, _infoLog);
		std::string errStr(_infoLog);
		std::cout << errStr << std::endl;
	}

	//创建着色shader
	_fragID = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(_fragID, 1, &_fShaderStr, NULL);
	glCompileShader(_fragID);

	glGetShaderiv(_fragID, GL_COMPILE_STATUS, &_successFlag);
	if (!_successFlag)
	{
		glGetShaderInfoLog(_fragID, 512, NULL, _infoLog);
		std::string errStr(_infoLog);
		std::cout << errStr << std::endl;
	}

	//创建shader程序
	shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, _vertexID);
	glAttachShader(shaderProgram, _fragID);
	glLinkProgram(shaderProgram);

	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &_successFlag);
	if (!_successFlag)
	{
		glGetProgramInfoLog(shaderProgram, 512, NULL, _infoLog);
		std::string errStr(_infoLog);
		std::cout << errStr << std::endl;
	}
	glDeleteShader(_vertexID);
	glDeleteShader(_fragID);
}

void initModel()
{
	float vertices[] = {
	-0.5f, -0.5f, 0.0f,
	 0.5f, -0.5f, 0.0f,
	 0.0f,  0.5f, 0.0f
	};
	glGenVertexArrays(1, &VAO);
	glBindVertexArray(VAO);

	glGenBuffers(1, &VBO);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(0);
	glBindVertexArray(0);
}

void render()
{
	glBindVertexArray(VAO);
	glUseProgram(shaderProgram);
	glDrawArrays(GL_TRIANGLES, 0, 3);
	glUseProgram(0);
}

int main()
{
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	GLFWwindow* window = glfwCreateWindow(800, 600, "OpenGL Core", NULL, NULL);
	if (window == NULL)
	{
		std::cout << "Failed to create GLFW window" << std::endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);

	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		std::cout << "Failed to initialize GLAD" << std::endl;
		return -1;
	}

	glViewport(0, 0, 800, 600);
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

	initModel();
	initShader("vertexShader.glsl", "fragmentShader.glsl");

	while (!glfwWindowShouldClose(window))
	{
		processInput(window);

		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		render();

		glfwSwapBuffers(window);
		glfwPollEvents();
	}

	glDeleteBuffers(1, &VBO);
	glDeleteProgram(shaderProgram);
	glfwTerminate();
	return 0;
}