高級OpenGL之Uniform緩衝對象（高級GLSL）

使用Uniform緩衝對象畫出四個不同顏色的立方體：

#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 "Shader.h"
#include "Camera.h"
#include "Model.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 *windows);
void scroll_callback(GLFWwindow *window, double xoffset, double yoffset);
unsigned int loadCubemap(vector<std::string> faces);


#define screenWidth 800
#define screenHeight 600

Camera camera(glm::vec3(0.0f, 0.0f, 3.0f));
float lastX = screenWidth / 2.0f;
float lastY = screenHeight / 2.0f;
bool firstMouse = true;

//timing
float deltaTime = 0.2f;
float lastFrame = 0.0f;

unsigned int cubeVAO,cubeVBO;
float cubeVertices[] = {
	// positions         
	-0.5f, -0.5f, -0.5f,
	0.5f, -0.5f, -0.5f,
	0.5f,  0.5f, -0.5f,
	0.5f,  0.5f, -0.5f,
	-0.5f,  0.5f, -0.5f,
	-0.5f, -0.5f, -0.5f,

	-0.5f, -0.5f,  0.5f,
	0.5f, -0.5f,  0.5f,
	0.5f,  0.5f,  0.5f,
	0.5f,  0.5f,  0.5f,
	-0.5f,  0.5f,  0.5f,
	-0.5f, -0.5f,  0.5f,

	-0.5f,  0.5f,  0.5f,
	-0.5f,  0.5f, -0.5f,
	-0.5f, -0.5f, -0.5f,
	-0.5f, -0.5f, -0.5f,
	-0.5f, -0.5f,  0.5f,
	-0.5f,  0.5f,  0.5f,

	0.5f,  0.5f,  0.5f,
	0.5f,  0.5f, -0.5f,
	0.5f, -0.5f, -0.5f,
	0.5f, -0.5f, -0.5f,
	0.5f, -0.5f,  0.5f,
	0.5f,  0.5f,  0.5f,

	-0.5f, -0.5f, -0.5f,
	0.5f, -0.5f, -0.5f,
	0.5f, -0.5f,  0.5f,
	0.5f, -0.5f,  0.5f,
	-0.5f, -0.5f,  0.5f,
	-0.5f, -0.5f, -0.5f,

	-0.5f,  0.5f, -0.5f,
	0.5f,  0.5f, -0.5f,
	0.5f,  0.5f,  0.5f,
	0.5f,  0.5f,  0.5f,
	-0.5f,  0.5f,  0.5f,
	-0.5f,  0.5f, -0.5f,
};
glm::mat4 model = glm::mat4(1.0f);
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(screenWidth, screenHeight, "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_DEPTH_TEST);

	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, 3 * sizeof(float), (void*)0);
	glBindVertexArray(0);


	Shader shaderRed("uniform_buffer_object.vs", "red.fs");
	Shader shaderGreen("uniform_buffer_object.vs", "green.fs");
	Shader shaderBlue("uniform_buffer_object.vs", "blue.fs");
	Shader shaderYellow("uniform_buffer_object.vs", "yellow.fs");

	unsigned int uboMatrices;		//創建Uniform緩衝對象本身，並將其綁定到綁定點0
	glGenBuffers(1, &uboMatrices);		//創建一個Uniform緩衝對象，並將它綁定到GL_UNIFORM_BUFFER目標，並調用glBufferData，分配足夠的內存。
	glBindBuffer(GL_UNIFORM_BUFFER, uboMatrices);
	glBufferData(GL_UNIFORM_BUFFER, 2*sizeof(glm::mat4), NULL, GL_STATIC_DRAW);	//分配152字節的內存
	glBindBuffer(GL_UNIFORM_BUFFER, 0);

	glBindBufferRange(GL_UNIFORM_BUFFER, 0, uboMatrices, 0, 2 * sizeof(glm::mat4));

	unsigned int uniformBlockIndexRed = glGetUniformBlockIndex(shaderRed.ID, "Matrices");	//參數爲一個程序對象和Uniform塊的名稱
	unsigned int uniformBlockIndexGreen = glGetUniformBlockIndex(shaderGreen.ID, "Matrices");	//參數爲一個程序對象和Uniform塊的名稱
	unsigned int uniformBlockIndexBlue = glGetUniformBlockIndex(shaderBlue.ID, "Matrices");
	unsigned int uniformBlockIndexYellow = glGetUniformBlockIndex(shaderYellow.ID, "Matrices");
	
	glUniformBlockBinding(shaderRed.ID, uniformBlockIndexRed, 0);	//將Uniform塊綁定到一個特定的綁定點中，第一個參數是一個程序對象，之後是一個Uniform塊索引和鏈接到的綁定點
	glUniformBlockBinding(shaderGreen.ID, uniformBlockIndexGreen, 0);
	glUniformBlockBinding(shaderBlue.ID, uniformBlockIndexBlue, 0);
	glUniformBlockBinding(shaderYellow.ID, uniformBlockIndexYellow, 0);
	
	glm::mat4 projection = glm::perspective(glm::radians(45.0f), (float)screenWidth / (float)screenHeight, 0.1f, 100.0f);
	glBindBuffer(GL_UNIFORM_BUFFER, uboMatrices);
	glBufferSubData(GL_UNIFORM_BUFFER, 0, sizeof(glm::mat4), glm::value_ptr(projection));
	glBindBuffer(GL_UNIFORM_BUFFER, 0);


	while (!glfwWindowShouldClose(window))
	{
		float currentFrame = glfwGetTime();
		deltaTime = currentFrame - lastFrame;
		lastFrame = currentFrame;
		processInput(window);
		glClearColor(0.05f, 0.05f, 0.05f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

		//set the view matrix
		glm::mat4 view = camera.GetViewMatrix();
		glBindBuffer(GL_UNIFORM_BUFFER, uboMatrices);
		glBufferSubData(GL_UNIFORM_BUFFER, sizeof(glm::mat4), sizeof(glm::mat4), glm::value_ptr(view));
		glBindBuffer(GL_UNIFORM_BUFFER, 0);

		//draw 4 cubes
		//RED
		glBindVertexArray(cubeVAO);
		shaderRed.use();
		glm::mat4 model = glm::mat4(1.0f);
		model = glm::translate(model, glm::vec3(-0.75f, 0.75f, 0.0f));//move top-left
		shaderRed.setMat4("model", model);
		glDrawArrays(GL_TRIANGLES, 0, 36);

		//GREEN
		shaderGreen.use();
		model = glm::mat4(1.0f);
		model = glm::translate(model, glm::vec3(0.75f, 0.75f, 0.0f));
		shaderGreen.setMat4("model", model);
		glDrawArrays(GL_TRIANGLES, 0, 36);

		//YELLOW
		shaderYellow.use();
		model = glm::mat4(1.0f);
		model = glm::translate(model, glm::vec3(-0.75f, -0.75f, 0.0f));
		shaderYellow.setMat4("model", model);
		glDrawArrays(GL_TRIANGLES, 0, 36);

		//BLUE
		shaderBlue.use();
		model = glm::mat4(1.0f);
		model = glm::translate(model, glm::vec3(0.75f, -0.75f, 0.0f));
		shaderBlue.setMat4("model", model);
		glDrawArrays(GL_TRIANGLES, 0, 36);


		glfwSwapBuffers(window);
		glfwPollEvents();
	}
	glDeleteVertexArrays(1, &cubeVAO);
	glDeleteBuffers(1, &cubeVBO);
	glfwTerminate();
	return 0;
}
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 loadCubemap(vector<std::string> faces)	//創建立方體貼圖
{
	unsigned int textureID;
	glGenTextures(1, &textureID);
	glBindTexture(GL_TEXTURE_CUBE_MAP, textureID);

	int width, height, nrChannels;
	for (unsigned int i = 0; i < faces.size(); i++)
	{
		unsigned char *data = stbi_load(faces[i].c_str(), &width, &height, &nrChannels, 0);
		if (data)
		{
			glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
			stbi_image_free(data);
		}
		else
		{
			std::cout << "Cubemap texture failed to load at path: " << faces[i] << std::endl;
			stbi_image_free(data);
		}
	}
	glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
	glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
	glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);

	return textureID;
}

uniform_buffer_object.vs（頂點着色器）:

#version 330 core
layout(location=0)in vec3 aPos;
layout (std140) uniform Matrices
{
	mat4 projection;
	mat4 view;
};
uniform mat4 model;
void main()
{
	gl_Position=projection*view*model*vec4(aPos,1.0);
}

紅色片段着色器示例：

#version 330 core
out vec4 FragColor;
void main()
{
    FragColor=vec4(1.0,0.0,0.0,1.0);
}