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前一个教程： 小控件的姿势
下一个教程： 创建小控件

目标

在本教程中，你将学习如何

• 如何使用 makeTransformToGlobal 计算姿势
• 如何使用 makeCameraPose 和 Viz3d::setViewerPose
• 如何通过轴和观察截锥体来可视化相机位置

代码

你可以从 此处 下载代码。

 
#include <opencv2/viz.hpp>
#include <iostream>
#include <fstream>
 
using namespace cv;
using namespace std;
 
static void help()
{
cout
<< "--------------------------------------------------------------------------" << endl
<< "该程序展示了如何使用 makeTransformToGlobal() 计算所需的姿势，"
<< "如何使用 makeCameraPose 和 Viz3d::setViewerPose。你可以观察场景 "
<< "来自相机视点 (C) 或全局视点 (G)" << endl
<< "用法:" << 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 << "输入参数缺失" << endl;
        return 1;
    }
 
    bool camera_pov = (argv[1][0] == 'C');
 
    viz::Viz3d myWindow("坐标系");
 
myWindow.showWidget("坐标轴", 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); // 坐标轴
        viz::WCameraPosition cpw_frustum(Vec2f(0.889484, 0.523599)); // 相机视锥
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

以下是程序的一般结构

• 创建一个可视化窗口。

   
  viz::Viz3d myWindow("Transformations");

• 根据摄像机位置、摄像机焦距和 y 方向获取摄像机姿态。

   
  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);

• 知道摄像机坐标系轴的情况下，获取变换矩阵。

   
  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);

• 根据 bunny.ply 文件创建云小组件

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

• 根据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;

• 如果将视点设置为全局，则可视化摄像机坐标系和视椎空间。

   
  if (!camera_pov)
  {
      viz::WCameraPosition cpw(0.5); // 坐标轴
      viz::WCameraPosition cpw_frustum(Vec2f(0.889484, 0.523599)); // 相机视锥
  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组件

   
  myWindow.showWidget("bunny", cloud_widget, cloud_pose_global);

• 如果将视点设置为摄像机，则将查看器姿态设置为cam_pose。

   
  if (camera_pov)
  myWindow.setViewerPose(cam_pose);

结果

1. 以下是从摄像机视点获得的结果。

1. 以下是从全局视点获得的结果。