luca-penasa · February 14, 2017 16:33 · Feb 18, 2016 · Feb 18, 2016 · Feb 18, 2016
diff --git a/make_vtk_camera.cpp b/make_vtk_camera.cpp
@@ -47,3 +47,25 @@ vtkSmartPointer<vtkCamera> make_vtk_camera(double focal_len,
 
   return camera;
 }
+
+
+/** 
+ * Helper function: Convert rotation and translation into a vtk 4x4 homogeneous transform
+ */
+vtkSmartPointer<vtkMatrix4x4> make_transform(vgl_rotation_3d<double> const& R,
+                                             vgl_vector_3d<double> const& T)
+{
+  vtkSmartPointer<vtkMatrix4x4> m = vtkSmartPointer<vtkMatrix4x4>::New();
+  vnl_matrix_fixed<double,3,3> R_mat = R.as_matrix();
+  for (int r=0; r<3; ++r) {
+    for (int c=0; c<3; ++c) {
+      m->SetElement(r,c,R_mat[r][c]);
+    }
+  }
+  m->SetElement(0,3,T.x());
+  m->SetElement(1,3,T.y());
+  m->SetElement(2,3,T.z());
+  m->SetElement(3,3,1);
+
+  return m;
+}
diff --git a/make_vtk_camera.cpp b/make_vtk_camera.cpp
@@ -29,6 +29,7 @@ vtkSmartPointer<vtkCamera> make_vtk_camera(double focal_len,
   camera->SetPosition(0, 0, 0);
   // look in the +Z direction of the camera coordinate system
   camera->SetFocalPoint(0, 0, 1);
+  // the camera Y axis points down
   camera->SetViewUp(0,-1,0);
 
   // ensure the relevant range of depths are rendered

diff --git a/make_vtk_camera.cpp b/make_vtk_camera.cpp
@@ -0,0 +1,48 @@
+/**
+ * Convert standard camera intrinsic and extrinsic parameters to a vtkCamera instance for rendering
+ * Assume square pixels and 0 skew (for now).
+ *
+ * focal_len : camera focal length (units pixels)
+ * nx,ny : image dimensions in pixels
+ * principal_pt: camera principal point,
+ *    i.e. the intersection of the principal ray with the image plane (units pixels)
+ * camera_rot, camera_trans : rotation, translation matrix mapping world points to camera coordinates
+ * depth_min, depth_max : needed to set the clipping range
+ *
+ **/
+vtkSmartPointer<vtkCamera> make_vtk_camera(double focal_len,
+                                           int nx, int ny,
+                                           vgl_point_2d<double> const& principal_pt,
+                                           vgl_rotation_3d<double> const& camera_rot,
+                                           vgl_vector_3d<double> const& camera_trans,
+                                           double depth_min, double depth_max)
+{
+  // create the camera
+  vtkSmartPointer<vtkCamera> camera = vtkSmartPointer<vtkCamera>::New();
+
+  // convert camera rotation and translation into a 4x4 homogeneous transformation matrix
+  vtkSmartPointer<vtkMatrix4x4> camera_RT = make_transform(camera_rot, camera_trans);
+  // apply the transform to scene objects
+  camera->SetModelTransformMatrix( camera_RT );
+
+  // the camera can stay at the origin because we are transforming the scene objects
+  camera->SetPosition(0, 0, 0);
+  // look in the +Z direction of the camera coordinate system
+  camera->SetFocalPoint(0, 0, 1);
+  camera->SetViewUp(0,-1,0);
+
+  // ensure the relevant range of depths are rendered
+  camera->SetClippingRange(depth_min, depth_max);
+
+  // convert the principal point to window center (normalized coordinate system) and set it
+  double wcx = -2*(principal_pt.x() - double(nx)/2) / nx;
+  double wcy =  2*(principal_pt.y() - double(ny)/2) / ny;
+  camera->SetWindowCenter(wcx, wcy);
+
+  // convert the focal length to view angle and set it
+  double view_angle = vnl_math::deg_per_rad * (2.0 * std::atan2( ny/2.0, focal_len ));
+  std::cout << "view_angle = " << view_angle << std::endl;
+  camera->SetViewAngle( view_angle );
+
+  return camera;
+}