tutorial code for makeTransformToGlobal, makeCameraPose, minor fixes in widget_pose tutorial

samples/cpp/tutorial_code/viz/transformations.cpp

+/**
+ * @file transformations.cpp
+ * @brief Visualizing cloud in different positions, coordinate frames, camera frustums
+ * @author Ozan Cagri Tonkal
+ */
+
+#include <opencv2/viz.hpp>
+#include <iostream>
+
+using namespace cv;
+using namespace std;
+
+/**
+ * @function help
+ * @brief Display instructions to use this tutorial program
+ */
+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
+    << "./coordinate_frame [ G | C ]"                                                 << endl
+    << endl;
+}
+
+/**
+ * @function main
+ */
+int main(int argn, char **argv)
+{
+    help();
+    
+    if (argn < 2)
+    {
+        cout << "Missing arguments." << endl;
+        return 1;
+    }
+    
+    bool camera_pov = (argv[1][0] == 'C');
+    
+    /// Create a window
+    viz::Viz3d myWindow("Coordinate Frame");
+    
+    /// Add coordinate axes
+    myWindow.showWidget("Coordinate Widget", viz::CoordinateSystemWidget());
+    
+    /// Let's assume camera has the following properties
+    Point3f cam_pos(3.0f,3.0f,3.0f), cam_focal_point(3.0f, 3.0f, 2.0f), cam_y_dir(-1.0,0.0,0.0);
+    /// We can get the pose of the cam using makeCameraPose
+    Affine3f cam_pose = viz::makeCameraPose(cam_pos, cam_focal_point, cam_y_dir);
+    /// We can get the transformation matrix from camera coordinate system to global using
+    /// - makeTransformToGlobal. We need the axes of the camera
+    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);
+    
+    /// Create a cloud widget.
+    viz::SphereWidget sphere_widget(Point3f(0.0,0.0,0.0), 0.5, 10, viz::Color::red());
+    
+    /// Pose of the widget in camera frame
+    Affine3f sphere_pose = Affine3f().translate(Vec3f(0.0f,0.0f,3.0f));
+    /// Pose of the widget in global frame
+    Affine3f sphere_pose_global = transform * sphere_pose;
+    
+    /// Visualize camera frame
+    if (!camera_pov)
+    {
+        viz::CameraPositionWidget cpw(0.5); // Coordinate axes
+        viz::CameraPositionWidget cpw_frustum(Vec2f(0.889484, 0.523599)); // Camera frustum
+        myWindow.showWidget("CPW", cpw, cam_pose);
+        myWindow.showWidget("CPW_FRUSTUM", cpw_frustum, cam_pose);
+    }
+    
+    /// Visualize widget
+    myWindow.showWidget("sphere", sphere_widget, sphere_pose_global);
+    
+    /// Set the viewer pose to that of camera
+    if (camera_pov)
+        myWindow.setViewerPose(cam_pose);
+    
+    /// Start event loop.
+    myWindow.spin();
+    
+    return 0;
+}

samples/cpp/tutorial_code/viz/widget_pose.cpp

 /**
- * @file creating_widgets.cpp
- * @brief Creating custom widgets using VTK
+ * @file widget_pose.cpp
+ * @brief Setting pose of a widget
  * @author Ozan Cagri Tonkal
  */
 
@@ -20,9 +20,9 @@ void help()
     cout
     << "--------------------------------------------------------------------------"   << endl
     << "This program shows how to visualize a cube rotated around (1,1,1) and shifted "
-    << "using Rodrigues matrix."                                                      << endl
+    << "using Rodrigues vector."                                                      << endl
     << "Usage:"                                                                       << endl
-    << "./coordinate_frame"                                                           << endl
+    << "./widget_pose"                                                                << endl
     << endl;
 }