高級OpenGL之模板測試

和深度測試一樣，對模板緩衝應該通過還是失敗，以及它應該如何影響模板緩衝，有一定控制。一共有兩個函數能夠用來配置模板測試: glStencilFunc和glStencilOp

glStencilFunc(GLenum func, GLint ref,Gluint mask)一共包含三個參數:

func：設置模板測試函數。用於比較已儲存的模板值上和glStencilFunc函數的ref值上。可用的選項有:GL_NEVER,GL_LESS,GL_LEQUAL,GL_GREATER,GL_GEQUAL,GL_EQUAL,GL_NOTEQUAL和GL_ALWAYS。

ref:設置了模板測試的參考值。模板緩衝的內容將會與這個值進行比較。

mask:設置一個掩碼，它將會與參考值和儲存的模板值在測試比較它們之前進行與（AND）運算。初始情況下所有位都爲1.

指示如何更新緩衝，需要glStencilOp函數：

glStencilOp(GLenum sfail,GLenum dpfail,GLenum dppass)一共包含三個選項，

sfail:模板測試失敗時採取的行爲

dpfail:模板測試通過，但深度測試失敗時採取的行爲。

dppass：模板測試和深度測試都通過時採取的行爲。

模板測試小節代碼實現：

#include <iostream>
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <fstream>
#include <sstream>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
//#include <boost/filesystem.cpp>
#define STB_IMAGE_IMPLEMENTATION
#include <stb_image.h>

#include "Shader.h"
#include "Camera.h"
#define _USE_MATH_DEFINES
#include<math.h>
void framebuffer_size_callback(GLFWwindow* windows, int width, int height);
void mouse_callback(GLFWwindow* window, double xpos, double ypos);
void processInput(GLFWwindow *window);
void scroll_callback(GLFWwindow *window, double xoffset, double yoffset);
unsigned int loadTexture(const char *path);
void DrawTwoContainers(Shader &normalShader);
void DrawTwoScaledUpContainers(Shader &shaderSingleColor);
//settings
const unsigned int SCR_WIDTH = 1280;
const unsigned int SCR_HEIGHT = 720;

#define ambient_light 0.1 //定義四個點光源的環境光影響
#define specular_light 0.05	// 定義四個點光源鏡面反射的影響


Camera camera(glm::vec3(0.0f, 0.0f, 3.0f));
float lastX = (float)SCR_HEIGHT/ 2.0f;
float lastY = (float)SCR_WIDTH / 2.0f;
bool firstMouse = true;
unsigned int cubeVAO, cubeVBO;
unsigned int cubeTexture;
unsigned int floorTexture;
//timing
float deltaTime = 0.0f;
float lastFrame = 0.0f;

int main()
{
	//glfw:initialize and configure
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
	GLFWwindow *window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "model_loading", NULL, NULL);
	if (window == NULL)
	{
		std::cout << "Failed to create GLFW window" << std::endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

	glfwSetCursorPosCallback(window, mouse_callback);
	glfwSetScrollCallback(window, scroll_callback);

	glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);


	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		std::cout << "Failed to initialize GLAD" << std::endl;
		return -1;
	}
	glEnable(GL_STENCIL_TEST);
	glDepthFunc(GL_LESS);
	//Model ourModel("D:/opengltask/LearnOpenGL-master/resources/objects/nanosuit/nanosuit.obj");
	float cubeVertices[] = {
		// positions          // texture Coords
		-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
	};
	float planeVertices[] = {
		// positions          // texture Coords (note we set these higher than 1 (together with GL_REPEAT as texture wrapping mode). this will cause the floor texture to repeat)
		5.0f, -0.5f,  5.0f,  2.0f, 0.0f,
		-5.0f, -0.5f,  5.0f,  0.0f, 0.0f,
		-5.0f, -0.5f, -5.0f,  0.0f, 2.0f,

		5.0f, -0.5f,  5.0f,  2.0f, 0.0f,
		-5.0f, -0.5f, -5.0f,  0.0f, 2.0f,
		5.0f, -0.5f, -5.0f,  2.0f, 2.0f
	};
	//對於立方體的VAO
	glGenVertexArrays(1, &cubeVAO);
	glGenBuffers(1, &cubeVBO);
	glBindVertexArray(cubeVAO);
	glBindBuffer(GL_ARRAY_BUFFER, cubeVBO);
	glBufferData(GL_ARRAY_BUFFER, sizeof(cubeVertices), &cubeVertices, GL_STATIC_DRAW);
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(1);
	glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
	glBindVertexArray(0);

	//對於平面的VAO
	unsigned int planeVAO, planeVBO;
	glGenVertexArrays(1, &planeVAO);
	glGenBuffers(1, &planeVBO);
	glBindVertexArray(planeVAO);
	glBindBuffer(GL_ARRAY_BUFFER, planeVBO);
	glBufferData(GL_ARRAY_BUFFER, sizeof(planeVertices), &planeVertices, GL_STATIC_DRAW);
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(1);
	glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
	glBindVertexArray(0);
	cubeTexture= loadTexture("D:/opengltask/LearnOpenGL-master/resources/textures/marble.jpg");
	floorTexture = loadTexture("D:/opengltask/LearnOpenGL-master/resources/textures/metal.png");
	Shader normalShader=Shader("1.1.depth_testing.vs", "1.1.depth_testing.fs");
	Shader shaderSingleColor=Shader("1.1.depth_testing.vs", "shaderSingleColor.fs");
	//加載紋理
	normalShader.use();
	//normalShader.setInt("texture1", 0);
	while (!glfwWindowShouldClose(window))
	{
		float currentFrame = glfwGetTime();
		deltaTime = currentFrame - lastFrame;
		lastFrame = currentFrame;

		//處理鍵盤輸入
		processInput(window);

		//渲染
		glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT|GL_STENCIL_BUFFER_BIT);	//將模板緩衝清楚爲0
		normalShader.use();
		glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);
		glm::mat4 view = camera.GetViewMatrix();
		normalShader.setMat4("projection", projection);
		normalShader.setMat4("view", view);
		shaderSingleColor.use();
		shaderSingleColor.setMat4("projection", projection);
		shaderSingleColor.setMat4("view", view);
		normalShader.use();
		//畫地板
		glStencilMask(0x00);	// 保證在繪製地板的時候不會更新模板緩衝
		glBindVertexArray(planeVAO);
		glBindTexture(GL_TEXTURE_2D, floorTexture);
		normalShader.setMat4("model", glm::mat4(1.0f));
		glDrawArrays(GL_TRIANGLES, 0, 6);
		glBindVertexArray(0);
		glEnable(GL_DEPTH_TEST);
		glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
		glStencilFunc(GL_ALWAYS, 1, 0xFF); //用於已儲存的模板值和ref之間進行比較,所有的片段都應該更新模板緩衝
		glStencilMask(0xFF);//啓用模板緩衝寫入

		normalShader.use();
		DrawTwoContainers(normalShader);

		glStencilFunc(GL_NOTEQUAL, 1, 0xFF);
		glStencilMask(0x00);	//禁止模板緩衝的寫入
		glDisable(GL_DEPTH_TEST);
		shaderSingleColor.use();
		DrawTwoScaledUpContainers(shaderSingleColor);
		
		glStencilMask(0xFF);
		glEnable(GL_DEPTH_TEST);
		glfwSwapBuffers(window);
		glfwPollEvents();
	}
	glDeleteVertexArrays(1, &cubeVAO);
	glDeleteVertexArrays(1, &planeVAO);
	glDeleteBuffers(1, &cubeVBO);
	glDeleteBuffers(1, &planeVBO);
	glfwTerminate();
	return 0;
}
void DrawTwoContainers(Shader &normalShader)
{
	//畫第一個立方體
	glBindVertexArray(cubeVAO);
	glActiveTexture(GL_TEXTURE0);
	glBindTexture(GL_TEXTURE_2D, cubeTexture);
	glm::mat4 model = glm::mat4(1.0f);
	model = glm::translate(model, glm::vec3(-1.0f, 0.0f, -1.0f));
	normalShader.setMat4("model", model);
	glDrawArrays(GL_TRIANGLES, 0, 36);
	//畫第二個立方體
	model = glm::mat4(1.0f);
	model = glm::translate(model, glm::vec3(2.0f, 0.0f, 0.0f));
	normalShader.setMat4("model", model);
	glDrawArrays(GL_TRIANGLES, 0, 36);
}
void DrawTwoScaledUpContainers(Shader &shaderSingleColor)
{
	//畫第一個立方體
	glBindVertexArray(cubeVAO);
	glActiveTexture(GL_TEXTURE0);
	glBindTexture(GL_TEXTURE_2D, cubeTexture);
	glm::mat4 model = glm::mat4(1.0f);
	model = glm::translate(model, glm::vec3(-1.0f, 0.0f, -1.0f));
	model = glm::scale(model, glm::vec3(1.1f, 1.1f, 1.1f));
	shaderSingleColor.setMat4("model", model);
	glDrawArrays(GL_TRIANGLES, 0, 36);
	//畫第二個立方體
	model = glm::mat4(1.0f);
	model = glm::translate(model, glm::vec3(2.0f, 0.0f, 0.0f));
	model = glm::scale(model, glm::vec3(1.1f, 1.1f, 1.1f));
	shaderSingleColor.setMat4("model", model);
	glDrawArrays(GL_TRIANGLES, 0, 36);
}
void framebuffer_size_callback(GLFWwindow* window, int width, int height)	//視口根據窗口大小調整的函數，兩個整數表示窗口的新維度
{
	glViewport(0, 0, width, height);
}
void processInput(GLFWwindow *window)	//輸入的控制
{
	if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
		camera.ProcessKeyboard(FORWARD, deltaTime);
	if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
		camera.ProcessKeyboard(BACKWARD, deltaTime);
	if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS)
		camera.ProcessKeyboard(LEFT, deltaTime);
	if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS)
		camera.ProcessKeyboard(RIGHT, deltaTime);

	/*if (glfwGetKey(window, GLFW_KEY_L) == GLFW_PRESS)
		model = glm::rotate(model, (float)(M_PI / 360.0), glm::vec3(0.0f, 1.0f, 0.0f));
	if (glfwGetKey(window, GLFW_KEY_R) == GLFW_PRESS)
		model = glm::rotate(model, (float)(-M_PI / 360.0), glm::vec3(0.0f, 1.0f, 0.0f));*/
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)	//	glfwGetKey函數需要一個窗口以及一個按鍵作爲輸入，函數將會返回這個按鍵是否正在被按下
		glfwSetWindowShouldClose(window, true);
}
void mouse_callback(GLFWwindow* window, double xpos, double ypos)	//鼠標回調函數
{
	if (firstMouse)
	{
		lastX = xpos;
		lastY = ypos;
		firstMouse = false;
	}
	float xoffset = xpos - lastX;
	float yoffset = lastY - ypos;	//相反的，因爲y座標是從底部往頂部依次增大的
	lastX = xpos;
	lastY = ypos;
	camera.ProcessMouseMovement(xoffset, yoffset);
}
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset)	//鼠標滾輪的回調函數
{
	camera.ProcessMouseScroll(yoffset);
}
unsigned int loadTexture(char const *path)
{
	unsigned int texture_id;
	glGenTextures(1, &texture_id);
	int width, height, nrChannels;
	unsigned char *data = stbi_load(path, &width, &height, &nrChannels, 0);
	if (data)
	{
		GLenum format;	//unsigned int 類型的別稱
		if (nrChannels == 1)
			format = GL_RED;
		else if (nrChannels == 3)
			format = GL_RGB;
		else if (nrChannels == 4)
			format = GL_RGBA;
		glBindTexture(GL_TEXTURE_2D, texture_id);
		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, format, GL_UNSIGNED_BYTE, data);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

		glGenerateMipmap(GL_TEXTURE_2D);

		stbi_image_free(data);
	}
	else
	{
		std::cout << "Failed to load texture at path:" <<path<< std::endl;
	}

	return texture_id;
}