Corrected behavior of the camera manipulator (backprojected diff-vect…

…or method)

Arrangement_on_surface_2/demo/earth/Camera.cpp

@@ -28,7 +28,7 @@ QMatrix4x4 Camera::get_view_matrix() const
 }
 
 
-void Camera::rotate(float theta, float phi)
+void Camera::rotate_from_init_config(float theta, float phi)
 {
   // TO-DO: use the following logic to eliminate the QT-deprecation warnings!
   //QMatrix4x4 rot;
@@ -72,6 +72,22 @@ void Camera::rotate(QMatrix4x4 rot)
   m_uz = rot * m_uz;
 }
 
+void Camera::save_config()
+{
+  m_saved_pos = m_pos;
+  m_saved_ux  = m_ux;
+  m_saved_uy  = m_uy;
+  m_saved_uz  = m_uz;
+}
+
+void Camera::rotate_from_saved_config(QMatrix4x4 rot)
+{
+  m_pos = rot * m_saved_pos;
+  m_ux =  rot * m_saved_ux;
+  m_uy =  rot * m_saved_uy;
+  m_uz =  rot * m_saved_uz;
+}
+
 void Camera::move_forward(float distance)
 {
   // recall that in OpenGL camera model, camera's z-axis points always

Arrangement_on_surface_2/demo/earth/Camera.h

@@ -25,9 +25,13 @@ class Camera
 
   // theta: angle around y-axis
   // phi: angle from the xz-plane (= rotated x-axis after the above rotation)
-  void rotate(float theta, float phi);
+  void rotate_from_init_config(float theta, float phi);
   void rotate(QMatrix4x4 rot);
 
+  // save config & rotate from saved config (move to separate class?)
+  void save_config();
+  void rotate_from_saved_config(QMatrix4x4 rot);
+
   // move the camera forward around its own z-axis
   void move_forward(float distance);
 
@@ -37,6 +41,11 @@ class Camera
   QVector3D m_uy;
   QVector3D m_uz;
 
+  QVector3D m_saved_pos;
+  QVector3D m_saved_ux;
+  QVector3D m_saved_uy;
+  QVector3D m_saved_uz;
+
   float m_z_near, m_z_far;
 
   QMatrix4x4 m_projection;

Arrangement_on_surface_2/demo/earth/Main_widget.cpp

@@ -34,7 +34,13 @@ void Main_widget::set_mouse_button_pressed_flag(QMouseEvent* e, bool flag)
 void Main_widget::mousePressEvent(QMouseEvent* e)
 {
   set_mouse_button_pressed_flag(e, true);
-  m_last_mouse_pos = QVector2D(e->position());
+  m_mouse_press_pos = m_last_mouse_pos = QVector2D(e->position());
+
+  // for the backprojected diff-vector method:
+  if (m_left_mouse_button_down)
+  {
+    m_camera.save_config();
+  }
 }
 void Main_widget::mouseMoveEvent(QMouseEvent* e)
 {
@@ -50,12 +56,13 @@ void Main_widget::mouseMoveEvent(QMouseEvent* e)
       // OUR CUSTOM AD-HOC CAMERA ROTATION
       m_theta += rotation_scale_factor * diff.x();
       m_phi += rotation_scale_factor * diff.y();
-      m_camera.rotate(-m_theta, -m_phi);
+      m_camera.rotate_from_init_config(-m_theta, -m_phi);
     }
     else
     {
       // ROTATION AROUND AN AXIS ORTHOGONAL TO THE BACKPROJECTED DIF-VECTOR
-      QVector3D p0(m_last_mouse_pos.x(), m_vp_height - m_last_mouse_pos.y(), 0);
+      //QVector3D p0(m_last_mouse_pos.x(), m_vp_height - m_last_mouse_pos.y(), 0);
+      QVector3D p0(m_mouse_press_pos.x(), m_vp_height - m_mouse_press_pos.y(), 0);
       QVector3D p1(current_mouse_pos.x(), m_vp_height - current_mouse_pos.y(), 0);
       auto dp = p1 - p0; // difference vector in OpenGL window coords.
       QVector3D rdp(-dp.y(), dp.x(), 0); // rotate diff-vector CCW by 90-deg
@@ -77,7 +84,7 @@ void Main_widget::mouseMoveEvent(QMouseEvent* e)
       QMatrix4x4 rot_matrix;
       rot_matrix.rotate(-rot_angle, rot_axis);
 
-      m_camera.rotate(rot_matrix);
+      m_camera.rotate_from_saved_config(rot_matrix);
     }
   }
   else if(m_middle_mouse_button_down)
@@ -108,23 +115,7 @@ void Main_widget::initializeGL()
   init_shader_programs();
 
   {
-    //// compute the back-projected error
-    //QRect vp(0, 0, m_vp_width, m_vp_height);
-    //auto proj = m_camera.get_projection_matrix();
-    //auto view = m_camera.get_view_matrix();
-    //QMatrix4x4 model;
-    //auto model_view = view * model;
-    //
-    //QVector3D p0(m_vp_width / 2, m_vp_height / 2, 0);
-    //QVector3D p1(p0.x() + 1, p0.y(), 0);
-    //auto wp0 = p0.unproject(model_view, proj, vp);
-    //auto wp1 = p1.unproject(model_view, proj, vp);
-    //const float z_near = 1.f;
-    //const float r = 1.f; // sphere radius
-    //const float d = m_camera.get_pos().distanceToPoint(QVector3D(0, 0, 0)) - r;
-    //float err = wp0.distanceToPoint(wp1) * (d / z_near);
-    //std::cout << "error = " << err << std::endl;
-
+    // TO-DO: move this code to resizeGL (when viewport is initialized)
     // has to be defined after camera has been defined:
     // because we want to compute the error based on camera parameters!
     Geodesic_arcs ga;

Arrangement_on_surface_2/demo/earth/Main_widget.h

@@ -66,6 +66,7 @@ class Main_widget : public QOpenGLWidget, protected OpenGLFunctionsBase
   bool m_left_mouse_button_down = false;
   bool m_middle_mouse_button_down = false;
   QVector2D m_last_mouse_pos;
+  QVector2D m_mouse_press_pos;
   float m_theta = 0, m_phi = 0;
   int   m_vp_width = 0, m_vp_height = 0;