orb-slam系列 开始(一)

1 系统架构

2 程序入口

    // Retrieve paths to images
    vector<string> vstrImageLeft;
    vector<string> vstrImageRight;
    vector<double> vTimeStamp;
    LoadImages(string(argv[3]), string(argv[4]), string(argv[5]), vstrImageLeft, vstrImageRight, vTimeStamp);

载入图片信息

```cpp
// Create SLAM system. It initializes all system threads and gets ready to process frames.
    ORB_SLAM2::System SLAM(argv[1],argv[2],ORB_SLAM2::System::STEREO,true);

开始建立了slam2对象。

   //初始化SLAM系统 。启动当地建图，回环检测和可视化器线程
    System(const string &strVocFile, const string &strSettingsFile, const eSensor sensor, const bool bUseViewer = true);

 /*******************************************************************************
 *     函数属性：类System的构造函数
 *     函数功能：（1）将配置文件读入到内存中，存储到fsSettings变量中
 *                        （2）将字典读入mpVocabulary变量中
 *                        （3）创建关键帧数据集
 *                        （4）创建全局地图
 *                        （5）初始化观测器（关键帧观测器、地图观测器）、图像追踪器、局部地图构建器、回环检测器、
 *                        （6）四个线程初始化（追踪线程（主线程）、局部地图构建线程、回环检测线程、观测器线程）
 *                        （7）四个线程之间建立联系
 *     函数参数介绍：
 *                          strVocFile：指向字典的路径
 *                          strSettingsFile：指向参数配置文件的路径
 *                          sensor：所使用传感器的种类
 *                          bUseViewer：是否打开实时观测标志
 *     备注：给类中的各个成员变量进行初始化
 * 
 ******************************************************************************/
System::System(const string &strVocFile, const string &strSettingsFile, const eSensor sensor,
               const bool bUseViewer):mSensor(sensor), mpViewer(static_cast<Viewer*>(NULL)), mbReset(false),mbActivateLocalizationMode(false),
        mbDeactivateLocalizationMode(false)
{
    // Output welcome message
    cout << endl <<
    "ORB-SLAM2 Copyright (C) 2014-2016 Raul Mur-Artal, University of Zaragoza." << endl <<
    "This program comes with ABSOLUTELY NO WARRANTY;" << endl  <<
    "This is free software, and you are welcome to redistribute it" << endl <<
    "under certain conditions. See LICENSE.txt." << endl << endl;

    cout << "Input sensor was set to: ";

    if(mSensor==MONOCULAR)
        cout << "Monocular" << endl;
    else if(mSensor==STEREO)
        cout << "Stereo" << endl;
    else if(mSensor==RGBD)
        cout << "RGB-D" << endl;

    //Check settings file   将配置文件读入到内存中，存储到fsSettings变量中
    cv::FileStorage fsSettings(strSettingsFile.c_str(), cv::FileStorage::READ);
    if(!fsSettings.isOpened())
    {
       cerr << "Failed to open settings file at: " << strSettingsFile << endl;
       exit(-1);
    }


    //Load ORB Vocabulary   
    cout << endl << "Loading ORB Vocabulary. This could take a while..." << endl;

    mpVocabulary = new ORBVocabulary();
    bool bVocLoad = mpVocabulary->loadFromTextFile(strVocFile); //将字典加载到mpVocabulary中
    if(!bVocLoad)
    {
        cerr << "Wrong path to vocabulary. " << endl;
        cerr << "Falied to open at: " << strVocFile << endl;
        exit(-1);
    }
    cout << "Vocabulary loaded!" << endl << endl;

    //Create KeyFrame Database 创建关键帧数据集
    mpKeyFrameDatabase = new KeyFrameDatabase(*mpVocabulary);

    //Create the Map  创建地图
    mpMap = new Map();

    //Create Drawers. These are used by the Viewer  创建观测器 帧的观测器和地图观测器
    mpFrameDrawer = new FrameDrawer(mpMap);
    mpMapDrawer = new MapDrawer(mpMap, strSettingsFile);

    //Initialize the Tracking thread  初始化跟踪线程器
    //(it will live in the main thread of execution, the one that called this constructor)  它运行在主线程中，这个线程被称作constructor
    mpTracker = new Tracking(this, mpVocabulary, mpFrameDrawer, mpMapDrawer,
                             mpMap, mpKeyFrameDatabase, strSettingsFile, mSensor);

    //Initialize the Local Mapping thread and launch   初始化当地地图线程并启动
    mpLocalMapper = new LocalMapping(mpMap, mSensor==MONOCULAR);
    mptLocalMapping = new thread(&ORB_SLAM2::LocalMapping::Run,mpLocalMapper);

    //Initialize the Loop Closing thread and launch    初始化回环检测线程并启动
    mpLoopCloser = new LoopClosing(mpMap, mpKeyFrameDatabase, mpVocabulary, mSensor!=MONOCULAR);
    mptLoopClosing = new thread(&ORB_SLAM2::LoopClosing::Run, mpLoopCloser);

    //Initialize the Viewer thread and launch   初始化观测器线程并启动
    if(bUseViewer)
    {
        mpViewer = new Viewer(this, mpFrameDrawer,mpMapDrawer,mpTracker,strSettingsFile);
        mptViewer = new thread(&Viewer::Run, mpViewer);
        mpTracker->SetViewer(mpViewer);
    }

    //Set pointers between threads   各个线程之间建立联系
    mpTracker->SetLocalMapper(mpLocalMapper);
    mpTracker->SetLoopClosing(mpLoopCloser);

    mpLocalMapper->SetTracker(mpTracker);
    mpLocalMapper->SetLoopCloser(mpLoopCloser);

    mpLoopCloser->SetTracker(mpTracker);
    mpLoopCloser->SetLocalMapper(mpLocalMapper);
}

slam2对象作用
1）将配置文件读入到内存中，存储到fsSettings变量中。
2）载入了orb 词典。
3）创建关键帧数据集mpKeyFrameDatabase。
4）创建地图，创建观测器。
5）Tracking主线程

mpTracker = new Tracking(this, mpVocabulary, mpFrameDrawer, mpMapDrawer,
                             mpMap, mpKeyFrameDatabase, strSettingsFile, mSensor);

6）LocalMapping线程

mpLocalMapper = new LocalMapping(mpMap, mSensor==MONOCULAR);
    mptLocalMapping = new thread(&ORB_SLAM2::LocalMapping::Run,mpLocalMapper);

7）LoopClosing线程

mpLoopCloser = new LoopClosing(mpMap, mpKeyFrameDatabase, mpVocabulary, mSensor!=MONOCULAR);
    mptLoopClosing = new thread(&ORB_SLAM2::LoopClosing::Run, mpLoopCloser)