目标

在本教程中，您将学习如何

• 如何使用makeTransformToGlobal来计算pose
• 如何使用makeCameraPose和Viz3d :: setViewerPose

• 如何用轴和视锥显示相机位置

Code

你可以从这里下载代码。

#include <opencv2/viz.hpp>
#include <iostream>
#include <fstream>
using namespace cv;
using namespace std;
static void help()
{
    cout
    << "--------------------------------------------------------------------------"   << endl
    << "This program shows how to use makeTransformToGlobal() to compute required pose,"
    << "how to use makeCameraPose and Viz3d::setViewerPose. You can observe the scene "
    << "from camera point of view (C) or global point of view (G)"                    << endl
    << "Usage:"                                                                       << endl
    << "./transformations [ G | C ]"                                                 << endl
    << endl;
}
static Mat cvcloud_load()
{
    Mat cloud(1, 1889, CV_32FC3);
    ifstream ifs("bunny.ply");
    string str;
    for(size_t i = 0; i < 12; ++i)
        getline(ifs, str);
    Point3f* data = cloud.ptr<cv::Point3f>();
    float dummy1, dummy2;
    for(size_t i = 0; i < 1889; ++i)
        ifs >> data[i].x >> data[i].y >> data[i].z >> dummy1 >> dummy2;
    cloud *= 5.0f;
    return cloud;
}
int main(int argn, char **argv)
{
    help();
    if (argn < 2)
    {
        cout << "Missing arguments." << endl;
        return 1;
    }
    bool camera_pov = (argv[1][0] == 'C');
    viz::Viz3d myWindow("Coordinate Frame");
    myWindow.showWidget("Coordinate Widget", viz::WCoordinateSystem());
    Vec3f cam_pos(3.0f,3.0f,3.0f), cam_focal_point(3.0f,3.0f,2.0f), cam_y_dir(-1.0f,0.0f,0.0f);
    Affine3f cam_pose = viz::makeCameraPose(cam_pos, cam_focal_point, cam_y_dir);
    Affine3f transform = viz::makeTransformToGlobal(Vec3f(0.0f,-1.0f,0.0f), Vec3f(-1.0f,0.0f,0.0f), Vec3f(0.0f,0.0f,-1.0f), cam_pos);
    Mat bunny_cloud = cvcloud_load();
    viz::WCloud cloud_widget(bunny_cloud, viz::Color::green());
    Affine3f cloud_pose = Affine3f().translate(Vec3f(0.0f,0.0f,3.0f));
    Affine3f cloud_pose_global = transform * cloud_pose;
    if (!camera_pov)
    {
        viz::WCameraPosition cpw(0.5); // Coordinate axes
        viz::WCameraPosition cpw_frustum(Vec2f(0.889484, 0.523599)); // Camera frustum
        myWindow.showWidget("CPW", cpw, cam_pose);
        myWindow.showWidget("CPW_FRUSTUM", cpw_frustum, cam_pose);
    }
    myWindow.showWidget("bunny", cloud_widget, cloud_pose_global);
    if (camera_pov)
        myWindow.setViewerPose(cam_pose);
    myWindow.spin();
    return 0;
}

说明

这是程序的一般结构：

• 创建一个可视化窗口。

viz :: Viz3d myWindow（“Transformations”）;

• 从相机位置，相机焦点和y方向获取相机姿势。
  

Point3f cam_pos（3.0f，3.0f，3.0f），cam_focal_point（3.0f，3.0f，2.0f），cam_y_dir（-1.0f，0.0f，0.0f）;
Affine3f cam_pose = viz :: makeCameraPose（cam_pos，cam_focal_point，cam_y_dir）;

• 获取摄像机坐标系轴的变换矩阵。
  

Affine3f transform = viz :: makeTransformToGlobal（Vec3f（0.0f，-1.0f，0.0f），Vec3f（-1.0f，0.0f，0.0f）），Vec3f（0.0f，0.0f，-1.0f），cam_pos）;

• 从bunny.ply文件创建一个云小部件
  

Mat bunny_cloud = cvcloud_load（）;
viz :: WCloud cloud_widget（bunny_cloud，viz :: Color :: green（））;

• 给定摄像机坐标系中的姿态，估计全局姿态。
  

Affine3f cloud_pose = Affine3f（）.translate（Vec3f（0.0f，0.0f，3.0f））;
Affine3f cloud_pose_global = transform * cloud_pose;

• 如果视点设置为全局，可视化摄像机坐标系和观察平截头体。
  

if (!camera_pov)
{
    viz::WCameraPosition cpw(0.5); // Coordinate axes
    viz::WCameraPosition cpw_frustum(Vec2f(0.889484, 0.523599)); // Camera frustum
    myWindow.showWidget("CPW", cpw, cam_pose);
    myWindow.showWidget("CPW_FRUSTUM", cpw_frustum, cam_pose);
}

• 使用估计的全局姿态可视化云小部件
  

myWindow.showWidget（“bunny”，cloud_widget，cloud_pose_global）;

• 如果视点设置为相机，请将观看者姿态设置为cam_pose。
  

if (camera_pov)
    myWindow.setViewerPose(cam_pose);

结果

1. 这是从相机视图点的结果。

• 这是全局视野的结果。