Home | History | Annotate | Download | only in transformations 
      1 Transformations {#tutorial_transformations}
      2 ===============
      3 
      4 Goal
      5 ----
      6 
      7 In this tutorial you will learn how to
      8 
      9 -   How to use makeTransformToGlobal to compute pose
     10 -   How to use makeCameraPose and Viz3d::setViewerPose
     11 -   How to visualize camera position by axes and by viewing frustum
     12 
     13 Code
     14 ----
     15 
     16 You can download the code from [here ](https://github.com/Itseez/opencv/tree/master/samples/cpp/tutorial_code/viz/transformations.cpp).
     17 @include samples/cpp/tutorial_code/viz/transformations.cpp
     18 
     19 Explanation
     20 -----------
     21 
     22 Here is the general structure of the program:
     23 
     24 -   Create a visualization window.
     25     @code{.cpp}
     26     /// Create a window
     27     viz::Viz3d myWindow("Transformations");
     28     @endcode
     29 -   Get camera pose from camera position, camera focal point and y direction.
     30     @code{.cpp}
     31     /// Let's assume camera has the following properties
     32     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);
     33 
     34     /// We can get the pose of the cam using makeCameraPose
     35     Affine3f cam_pose = viz::makeCameraPose(cam_pos, cam_focal_point, cam_y_dir);
     36     @endcode
     37 -   Obtain transform matrix knowing the axes of camera coordinate system.
     38     @code{.cpp}
     39     /// We can get the transformation matrix from camera coordinate system to global using
     40     /// - makeTransformToGlobal. We need the axes of the camera
     41     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);
     42     @endcode
     43 -   Create a cloud widget from bunny.ply file
     44     @code{.cpp}
     45     /// Create a cloud widget.
     46     Mat bunny_cloud = cvcloud_load();
     47     viz::WCloud cloud_widget(bunny_cloud, viz::Color::green());
     48     @endcode
     49 -   Given the pose in camera coordinate system, estimate the global pose.
     50     @code{.cpp}
     51     /// Pose of the widget in camera frame
     52     Affine3f cloud_pose = Affine3f().translate(Vec3f(0.0f,0.0f,3.0f));
     53     /// Pose of the widget in global frame
     54     Affine3f cloud_pose_global = transform * cloud_pose;
     55     @endcode
     56 -   If the view point is set to be global, visualize camera coordinate frame and viewing frustum.
     57     @code{.cpp}
     58     /// Visualize camera frame
     59     if (!camera_pov)
     60     {
     61         viz::WCameraPosition cpw(0.5); // Coordinate axes
     62         viz::WCameraPosition cpw_frustum(Vec2f(0.889484, 0.523599)); // Camera frustum
     63         myWindow.showWidget("CPW", cpw, cam_pose);
     64         myWindow.showWidget("CPW_FRUSTUM", cpw_frustum, cam_pose);
     65     }
     66     @endcode
     67 -   Visualize the cloud widget with the estimated global pose
     68     @code{.cpp}
     69     /// Visualize widget
     70     myWindow.showWidget("bunny", cloud_widget, cloud_pose_global);
     71     @endcode
     72 -   If the view point is set to be camera's, set viewer pose to **cam_pose**.
     73     @code{.cpp}
     74     /// Set the viewer pose to that of camera
     75     if (camera_pov)
     76         myWindow.setViewerPose(cam_pose);
     77     @endcode
     78 
     79 Results
     80 -------
     81 
     82 -#  Here is the result from the camera point of view.
     83 
     84     ![](images/camera_view_point.png)
     85 
     86 -#  Here is the result from global point of view.
     87 
     88     ![](images/global_view_point.png)
     89