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Structure from Motion C++

Hello All,

I am working on Structure from Motion. I think when it come to structure from motion, people would have came across MultiView Geometry book. It is a very good book but I found something confusing data in that book. In the below following code, there is function called Populate point cloud, which has two parameter pointcloud and pointcloud_RGB. I have point3d type values in pointcloud but I didn't find any about pointcloud_RGB in that book and it suddenly appears in this function, which is used to fill the VEC3d rgbv. Can some one please help who came across.

   void PopulatePCLPointCloud(const vector<cv::Point3d>& pointcloud, 
      const std::vector<cv::Vec3b>& pointcloud_RGB

    cout<<"Creating point cloud..."; 
    cloud.reset(new pcl::PointCloud<pcl::PointXYZRGB>); 

    for (unsigned int i=0; i<pointcloud.size(); i++) { 
    // get the RGB color value for the point 
            cv::Vec3b rgbv(255,255,255); 

    if (i < pointcloud_RGB.size()) { 
    rgbv = pointcloud_RGB[i]; 

            // check for erroneous coordinates (NaN, Inf, etc.) 
                    if (pointcloud[i].x != pointcloud[i].x || 
                            pointcloud[i].y != pointcloud[i].y || 
                            pointcloud[i].z != pointcloud[i].z || 
    #ifndef WIN32 
                            isnan(pointcloud[i].x) || 
                            isnan(pointcloud[i].y) || 
                            isnan(pointcloud[i].z) || 
                            _isnan(pointcloud[i].x) || 
                            _isnan(pointcloud[i].y) || 
                            _isnan(pointcloud[i].z) || 
    pcl::PointXYZRGB pclp; 
    pclp.x = pointcloud[i].x; 
    pclp.y = pointcloud[i].y; 
    pclp.z = pointcloud[i].z; 
    // RGB color, needs to be represented as an integer 
    uint32_t rgb = ((uint32_t)rgbv[2] << 16 | (uint32_t)rgbv[1] << 8 | 
    pclp.rgb = *reinterpret_cast<float*>(&rgb); 
    cloud->width = (uint32_t) cloud->points.size(); // number of points 
    cloud->height = 1; // a list of points, one row of data 

    //Create visualizer 

    pcl::visualization::CloudViewer viewer ("Simple Cloud Viewer"); 
    viewer.showCloud (cloud);