Set perspective angle automatically when the scale is changing.

2 files changed, 28 insertions, 0 deletions

diff --git a/geometry/screenbase.cpp b/geometry/screenbase.cpp
index b46a6da78c..fd5ce38f9b 100644
--- a/geometry/screenbase.cpp
+++ b/geometry/screenbase.cpp
@@ -75,6 +75,31 @@ void ScreenBase::UpdateDependentParameters()
   m_ClipRect = m_GlobalRect.GetGlobalRect();
 }
 
+double ScreenBase::CalculatePerspectiveAngle(double scale)
+{
+  double const kStartPerspectiveScale = 0.13e-4;
+  double const kMaxScale = 0.13e-5;
+  double const kMaxPerspectiveAngle = math::pi4;
+
+  if (scale > kStartPerspectiveScale)
+    return 0.0;
+  return kMaxPerspectiveAngle * (kStartPerspectiveScale - scale) / (kStartPerspectiveScale - kMaxScale);
+}
+
+void ScreenBase::UpdatePerspectiveParameters()
+{
+  double const angle = CalculatePerspectiveAngle(m_Scale);
+  if (angle > 0.0)
+  {
+    if (m_isPerspective)
+      SetRotationAngle(angle);
+    else
+      ApplyPerspective(angle, math::pi4, math::pi / 3);
+  }
+  else if (m_isPerspective)
+    ResetPerspective();
+}
+
 void ScreenBase::SetFromRects(m2::AnyRectD const & glbRect, m2::RectD const & pxRect)
 {
   double hScale = glbRect.GetLocalRect().SizeX() / pxRect.SizeX();
diff --git a/geometry/screenbase.hpp b/geometry/screenbase.hpp
index 93959d9998..ef5125d9e4 100644
--- a/geometry/screenbase.hpp
+++ b/geometry/screenbase.hpp
@@ -126,6 +126,7 @@ public:
   m2::AnyRectD const & GlobalRect() const { return m_GlobalRect; }
   m2::RectD const & ClipRect() const { return m_ClipRect; }
 
+  void UpdatePerspectiveParameters();
   void ApplyPerspective(double currentRotationAngle, double maxRotationAngle, double angleFOV);
   void ResetPerspective();
 
@@ -156,6 +157,8 @@ public:
                                      m2::PointD const & newPt1, m2::PointD const & newPt2,
                                      bool allowRotate);
 
+  static double CalculatePerspectiveAngle(double scale);
+
   /// Setting GtoP matrix extracts the Angle and m_Org parameters, leaving PixelRect intact
   void SetGtoPMatrix(MatrixT const & m);