OpenGL坐标系统--6

详细参考：这里

主要是坐标变换，变换又涉及坐标空间：局部空间、世界空间、观察空间、裁剪空间、屏幕空间。
变换矩阵：
模型矩阵：局部空间–>世界空间。
观察矩阵：世界空间–>观察空间。
投影矩阵：观察空间–>裁剪空间。
后续还需透视除法，标准化设备坐标，屏幕映射。

注：Unity中只需要操作到裁剪空间这样一步就可以了，后续的Unity会自动处理。
OpenGL是右手坐标系！！！
Unity里大部分空间都是左手坐标系，但观察空间是右手坐标系，系统会自动变换。
由于项目崩溃，新建项目时，glad的配置要按之前的教程进行配置，避免出现错误！

这节主要理论知识较多！

#include 
#include 
#include 

#include 
#include 
#include 

#include 

#include 

using namespace std;

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow* window);

const int SCR_WIDTH = 800;
const int SCR_HEIGHT = 600;


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

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

	GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "hahaha", NULL, NULL);
	if (window == NULL)
	{
		cout << "Failed to create GLFW window !" << endl;
		glfwTerminate();
		return -1;
	}

	glfwMakeContextCurrent(window);
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		cout << "Failed to init GLAD !" << endl;
	}

	//configure
	glEnable(GL_DEPTH_TEST);

	//build and compile shader
	Shader shader("Shaders/Learn6_coordinate.vs", "Shaders/Learn6_coordinate.fs");

	//set vertex data
	float vertices[] = {
	   -0.5f, -0.5f, -0.5f,  0.0f, 0.0f,
		0.5f, -0.5f, -0.5f,  1.0f, 0.0f,
		0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
		0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
	   -0.5f,  0.5f, -0.5f,  0.0f, 1.0f,
	   -0.5f, -0.5f, -0.5f,  0.0f, 0.0f,

	   -0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
		0.5f, -0.5f,  0.5f,  1.0f, 0.0f,
		0.5f,  0.5f,  0.5f,  1.0f, 1.0f,
		0.5f,  0.5f,  0.5f,  1.0f, 1.0f,
	   -0.5f,  0.5f,  0.5f,  0.0f, 1.0f,
	   -0.5f, -0.5f,  0.5f,  0.0f, 0.0f,

	   -0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
	   -0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
	   -0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
	   -0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
	   -0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
	   -0.5f,  0.5f,  0.5f,  1.0f, 0.0f,

		0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
		0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
		0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
		0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
		0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
		0.5f,  0.5f,  0.5f,  1.0f, 0.0f,

	   -0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
		0.5f, -0.5f, -0.5f,  1.0f, 1.0f,
		0.5f, -0.5f,  0.5f,  1.0f, 0.0f,
		0.5f, -0.5f,  0.5f,  1.0f, 0.0f,
	   -0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
	   -0.5f, -0.5f, -0.5f,  0.0f, 1.0f,

	   -0.5f,  0.5f, -0.5f,  0.0f, 1.0f,
		0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
		0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
		0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
	   -0.5f,  0.5f,  0.5f,  0.0f, 0.0f,
	   -0.5f,  0.5f, -0.5f,  0.0f, 1.0f
	};
	// world space positions of our cubes
	glm::vec3 cubePositions[] = {
		glm::vec3(0.0f,  0.0f,  0.0f),
		glm::vec3(2.0f,  5.0f, -15.0f),
		glm::vec3(-1.5f, -2.2f, -2.5f),
		glm::vec3(-3.8f, -2.0f, -12.3f),
		glm::vec3(2.4f, -0.4f, -3.5f),
		glm::vec3(-1.7f,  3.0f, -7.5f),
		glm::vec3(1.3f, -2.0f, -2.5f),
		glm::vec3(1.5f,  2.0f, -2.5f),
		glm::vec3(1.5f,  0.2f, -1.5f),
		glm::vec3(-1.3f,  1.0f, -1.5f)
	};

	//set buffer
	//create
	unsigned int VBO, VAO;
	glGenVertexArrays(1, &VAO);
	glGenBuffers(1, &VBO);

	//bind
	glBindVertexArray(VAO);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	//set data
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

	//set pointer:position
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
	glEnableVertexAttribArray(1);

	//load texture
	//create
	unsigned int texture1, texture2;
	//texture1
	glGenTextures(1, &texture1);
	//bind
	glBindTexture(GL_TEXTURE_2D, texture1);
	//set wrap para
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
	//set filtering para
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

	//load image
	int width, height, channels;

	//反转图片Y轴
	stbi_set_flip_vertically_on_load(true);

	unsigned char* data = stbi_load("Images/container.jpg", &width, &height, &channels, 0);
	if (data)
	{
		//set data
		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
		//generate minimap
		glGenerateMipmap(GL_TEXTURE_2D);
	}
	else
	{
		cout << "Failed to load texture !" << endl;
	}
	//释放图片内存
	stbi_image_free(data);

	//texture2
	glGenTextures(1, &texture2);
	//bind
	glBindTexture(GL_TEXTURE_2D, texture2);
	//set wrap para
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
	//set filtering para
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

	data = stbi_load("Images/awesomeface.png", &width, &height, &channels, 0);
	if (data)
	{
		//set data
		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
		//generate minimap
		glGenerateMipmap(GL_TEXTURE_2D);
	}
	else
	{
		cout << "Failed to load texture2 !" << endl;
	}
	//释放图片内存
	stbi_image_free(data);

	//set shader uniform value
	shader.use();//设置uniform值之前要先激活shader
	shader.setInt("texture1", 0);
	shader.setInt("texture2", 1);

	//render loop
	while (!glfwWindowShouldClose(window))
	{
		//input
		processInput(window);

		//render
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

		//bind texture on corresponding textue units
		glActiveTexture(GL_TEXTURE0);
		glBindTexture(GL_TEXTURE_2D, texture1);
		glActiveTexture(GL_TEXTURE1);
		glBindTexture(GL_TEXTURE_2D, texture2);

		//active shader
		shader.use();

		//create matrix transformations;
		glm::mat4 model = glm::mat4(1.0f);
		glm::mat4 view = glm::mat4(1.0f);
		glm::mat4 projection = glm::mat4(1.0f);
		view = glm::translate(view, glm::vec3(.0f, 0.0f, -3.0f));
		projection = glm::perspective(45.0f, (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);
		//set matrix
		shader.setMat4("model", model);
		shader.setMat4("view", view);
		shader.setMat4("projection", projection);

		//render boxes
		//bind data
		glBindVertexArray(VAO);
		for (unsigned i = 0; i < 10; i++)
		{
			model = glm::mat4(1.0f);
			model = glm::translate(model, cubePositions[i]);
			float angle = 20.0f * i;
			if (i % 3 != 0)
				model = glm::rotate(model, (float)glfwGetTime() * glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f));
			shader.setMat4("model", model);

			//draw
			glDrawArrays(GL_TRIANGLES, 0, 36);
		}

		//swap buffer
		glfwSwapBuffers(window);
		//call event
		glfwPollEvents();
	}

	//optional:de-allocate all resurces once they've outlived their pupose
	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	shader.deleteShader();


	//terminate clearing all previously allocated GLFW resources
	glfwTerminate();
	return 0;
}

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

void processInput(GLFWwindow* window)
{
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
	{
		glfwSetWindowShouldClose(window, true);
	}
}