Add getters for camera parameters #1419

library/private/camera_impl.h

@@ -50,6 +50,9 @@ class camera_impl : public camera
   camera& setState(const camera_state_t& state) override;
   camera_state_t getState() const override;
   void getState(camera_state_t& state) const override;
+  double getWorldAzimuth() const override;
+  double getWorldElevation() const override;
+  double getDistance() const override;
 
   camera& dolly(double val) override;
   camera& pan(double right, double up, double forward) override;
@@ -85,6 +88,13 @@ class camera_impl : public camera
   bool GetSuccessfullyReset() const;
 
 private:
+  /**
+   * This helper computes the direction vector pointing from the camera position
+   * toward the focal point in world coordinates:
+   * view = focal_point - position
+   */
+  void getPositionToFocalVector(vector3_t& vec) const;
+
   class internals;
   std::unique_ptr<internals> Internals;
 };

library/public/camera.h

@@ -68,7 +68,12 @@ class F3D_EXPORT camera
   [[nodiscard]] virtual camera_state_t getState() const = 0;
   /** Get the complete state of the camera into the provided arg */
   virtual void getState(camera_state_t& state) const = 0;
-
+  /** Return the camera azimuth angle in degrees */
+  [[nodiscard]] virtual double getWorldAzimuth() const = 0;
+  /** Return the camera elevation angle in degrees */
+  [[nodiscard]] virtual double getWorldElevation() const = 0;
+  /** Return the distance between the camera position and its focal point */
+  [[nodiscard]] virtual double getDistance() const = 0;
   ///@}
 
   ///@{ @name Manipulation

library/src/camera_impl.cxx

@@ -5,6 +5,8 @@
 #include <vtkRenderWindow.h>
 #include <vtkRenderer.h>
 #include <vtkVersion.h>
+#include <cmath>
+
 
 namespace f3d::detail
 {
@@ -103,6 +105,74 @@ void camera_impl::getFocalPoint(point3_t& foc) const
   cam->GetFocalPoint(foc.data());
 }
 
+//----------------------------------------------------------------------------
+  void camera_impl::getPositionToFocalVector(vector3_t& vec) const
+{
+  point3_t pos, focal;
+  this->getPosition(pos);
+  this->getFocalPoint(focal);
+
+  vtkMath::Subtract(pos.data(), focal.data(), vec.data());
+}
+
+//----------------------------------------------------------------------------
+  double camera_impl::getWorldAzimuth() const
+{
+  vector3_t view;
+  this->getPositionToFocalVector(view);
+  vtkMath::Normalize(view.data());
+
+  vtkRenderer* ren = this->Internals->VTKRenderer;
+  double* up = ren->GetEnvironmentUp();
+  double* right = ren->GetEnvironmentRight();
+
+  // Project view vector onto plane orthogonal to up
+  vector3_t projUp;
+  vtkMath::ProjectVector(view.data(), up, projUp.data());
+
+  vector3_t horizontal;
+  vtkMath::Subtract(view.data(), projUp.data(), horizontal.data());
+
+  static constexpr double EPS = 128 * std::numeric_limits<double>::epsilon();
+  if (vtkMath::Norm(horizontal.data()) < EPS)
+  {
+    return 0.0;
+  }
+
+  vtkMath::Normalize(horizontal.data());
+
+  // Signed angle between right and horizontal projection
+  double angleRad = vtkMath::SignedAngleBetweenVectors(right, horizontal.data(), up);
+
+  return vtkMath::DegreesFromRadians(angleRad);
+
+}
+
+//----------------------------------------------------------------------------
+  double camera_impl::getWorldElevation() const
+{
+  vector3_t view;
+  this->getPositionToFocalVector(view);
+  vtkMath::Normalize(view.data());
+
+  vtkRenderer* ren = this->Internals->VTKRenderer;
+  double* up = ren->GetEnvironmentUp();
+
+  // Elevation is angle above the horizontal plane
+  double dot = vtkMath::Dot(view.data(), up);
+  dot = std::clamp(dot, -1.0, 1.0);
+
+  return vtkMath::DegreesFromRadians(std::asin(dot));
+}
+
+//----------------------------------------------------------------------------
+  double camera_impl::getDistance() const
+{
+  vector3_t v;
+  this->getPositionToFocalVector(v);
+  return vtkMath::Norm(v.data());
+}
+
 //----------------------------------------------------------------------------
 camera& camera_impl::setViewUp(const vector3_t& up)
 {

library/testing/TestSDKCamera.cxx

@@ -219,6 +219,33 @@ int TestSDKCamera([[maybe_unused]] int argc, [[maybe_unused]] char* argv[])
     return EXIT_FAILURE;
   }
 
+  // Test getters: azimuth / elevation / distance
+  cam.setPosition({ 0., -11., -1. });
+  cam.setFocalPoint({ 0., 0., -1. });
+  cam.setViewUp({ 1., 0., 0. });
+
+  double azimuth = cam.getWorldAzimuth();
+  double elevation = cam.getWorldElevation();
+  double distance = cam.getDistance();
+
+  if (!compareDouble(distance, 11.0))
+  {
+    std::cerr << "getDistance is not behaving as expected: " << distance << "\n";
+    return EXIT_FAILURE;
+  }
+
+  if (!compareDouble(azimuth, 90.0))
+  {
+    std::cerr << "getAzimuth is not behaving as expected: " << azimuth << "\n";
+    return EXIT_FAILURE;
+  }
+
+  if (!compareDouble(elevation, 0.0))
+  {
+    std::cerr << "getElevation is not behaving as expected: " << elevation << "\n";
+    return EXIT_FAILURE;
+  }
+
   // Test dolly
   cam.dolly(10);
   expectedPos = { 20.9, -11., -12. };