2013-09-08 00:23:26 +08:00
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.. _transformations:
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Transformations
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***************
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Goal
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====
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In this tutorial you will learn how to
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.. container:: enumeratevisibleitemswithsquare
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* How to use makeTransformToGlobal to compute pose
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* How to use makeCameraPose and Viz3d::setViewerPose
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* How to visualize camera position by axes and by viewing frustum
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Code
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====
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2013-09-18 02:17:13 +08:00
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You can download the code from :download:`here <../../../../samples/cpp/tutorial_code/viz/transformations.cpp>`.
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2013-09-08 00:23:26 +08:00
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.. code-block:: cpp
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#include <opencv2/viz.hpp>
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#include <iostream>
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#include <fstream>
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using namespace cv;
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using namespace std;
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2014-11-27 18:23:24 +08:00
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/*
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2013-09-08 00:23:26 +08:00
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* @function cvcloud_load
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* @brief load bunny.ply
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*/
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Mat cvcloud_load()
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{
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Mat cloud(1, 1889, CV_32FC3);
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ifstream ifs("bunny.ply");
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string str;
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for(size_t i = 0; i < 12; ++i)
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getline(ifs, str);
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Point3f* data = cloud.ptr<cv::Point3f>();
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float dummy1, dummy2;
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for(size_t i = 0; i < 1889; ++i)
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ifs >> data[i].x >> data[i].y >> data[i].z >> dummy1 >> dummy2;
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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cloud *= 5.0f;
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return cloud;
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}
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2014-11-27 18:23:24 +08:00
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/*
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2013-09-08 00:23:26 +08:00
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* @function main
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*/
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int main(int argn, char **argv)
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2013-09-18 19:50:55 +08:00
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{
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2013-09-08 00:23:26 +08:00
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if (argn < 2)
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{
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cout << "Usage: " << endl << "./transformations [ G | C ]" << endl;
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return 1;
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}
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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bool camera_pov = (argv[1][0] == 'C');
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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/// Create a window
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viz::Viz3d myWindow("Coordinate Frame");
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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/// Add coordinate axes
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2013-09-15 22:26:53 +08:00
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myWindow.showWidget("Coordinate Widget", viz::WCoordinateSystem());
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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/// Let's assume camera has the following properties
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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);
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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/// We can get the pose of the cam using makeCameraPose
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Affine3f cam_pose = viz::makeCameraPose(cam_pos, cam_focal_point, cam_y_dir);
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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/// We can get the transformation matrix from camera coordinate system to global using
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/// - makeTransformToGlobal. We need the axes of the camera
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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);
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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/// Create a cloud widget.
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Mat bunny_cloud = cvcloud_load();
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2013-09-15 22:26:53 +08:00
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viz::WCloud cloud_widget(bunny_cloud, viz::Color::green());
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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/// Pose of the widget in camera frame
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Affine3f cloud_pose = Affine3f().translate(Vec3f(0.0f,0.0f,3.0f));
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/// Pose of the widget in global frame
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Affine3f cloud_pose_global = transform * cloud_pose;
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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/// Visualize camera frame
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if (!camera_pov)
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{
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2013-09-15 22:26:53 +08:00
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viz::WCameraPosition cpw(0.5); // Coordinate axes
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viz::WCameraPosition cpw_frustum(Vec2f(0.889484, 0.523599)); // Camera frustum
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2013-09-08 00:23:26 +08:00
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myWindow.showWidget("CPW", cpw, cam_pose);
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myWindow.showWidget("CPW_FRUSTUM", cpw_frustum, cam_pose);
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}
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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/// Visualize widget
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myWindow.showWidget("bunny", cloud_widget, cloud_pose_global);
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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/// Set the viewer pose to that of camera
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if (camera_pov)
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myWindow.setViewerPose(cam_pose);
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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/// Start event loop.
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myWindow.spin();
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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return 0;
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}
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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Explanation
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===========
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Here is the general structure of the program:
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* Create a visualization window.
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.. code-block:: cpp
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/// Create a window
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viz::Viz3d myWindow("Transformations");
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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* Get camera pose from camera position, camera focal point and y direction.
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.. code-block:: cpp
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/// Let's assume camera has the following properties
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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);
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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/// We can get the pose of the cam using makeCameraPose
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Affine3f cam_pose = viz::makeCameraPose(cam_pos, cam_focal_point, cam_y_dir);
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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* Obtain transform matrix knowing the axes of camera coordinate system.
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.. code-block:: cpp
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/// We can get the transformation matrix from camera coordinate system to global using
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/// - makeTransformToGlobal. We need the axes of the camera
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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);
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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* Create a cloud widget from bunny.ply file
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.. code-block:: cpp
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/// Create a cloud widget.
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Mat bunny_cloud = cvcloud_load();
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2013-09-15 22:26:53 +08:00
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viz::WCloud cloud_widget(bunny_cloud, viz::Color::green());
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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* Given the pose in camera coordinate system, estimate the global pose.
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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.. code-block:: cpp
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/// Pose of the widget in camera frame
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Affine3f cloud_pose = Affine3f().translate(Vec3f(0.0f,0.0f,3.0f));
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/// Pose of the widget in global frame
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Affine3f cloud_pose_global = transform * cloud_pose;
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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* If the view point is set to be global, visualize camera coordinate frame and viewing frustum.
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.. code-block:: cpp
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/// Visualize camera frame
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if (!camera_pov)
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{
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2013-09-15 22:26:53 +08:00
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viz::WCameraPosition cpw(0.5); // Coordinate axes
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viz::WCameraPosition cpw_frustum(Vec2f(0.889484, 0.523599)); // Camera frustum
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2013-09-08 00:23:26 +08:00
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myWindow.showWidget("CPW", cpw, cam_pose);
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myWindow.showWidget("CPW_FRUSTUM", cpw_frustum, cam_pose);
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}
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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* Visualize the cloud widget with the estimated global pose
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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.. code-block:: cpp
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/// Visualize widget
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myWindow.showWidget("bunny", cloud_widget, cloud_pose_global);
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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* If the view point is set to be camera's, set viewer pose to **cam_pose**.
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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.. code-block:: cpp
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/// Set the viewer pose to that of camera
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if (camera_pov)
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myWindow.setViewerPose(cam_pose);
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2013-09-18 19:50:55 +08:00
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2013-09-08 00:23:26 +08:00
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Results
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=======
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#. Here is the result from the camera point of view.
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.. image:: images/camera_view_point.png
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:alt: Camera Viewpoint
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:align: center
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#. Here is the result from global point of view.
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.. image:: images/global_view_point.png
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:alt: Global Viewpoint
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:align: center
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