fix aspect_ratio computation from fovs, add casting for camerapositionwidget, trajectorywidget

modules/viz/include/opencv2/viz/widgets.hpp

@@ -231,6 +231,8 @@ namespace cv
         template<> CV_EXPORTS TextWidget Widget::cast<TextWidget>();
         template<> CV_EXPORTS ImageOverlayWidget Widget::cast<ImageOverlayWidget>();
         template<> CV_EXPORTS Image3DWidget Widget::cast<Image3DWidget>();
+        template<> CV_EXPORTS CameraPositionWidget Widget::cast<CameraPositionWidget>();
+        template<> CV_EXPORTS TrajectoryWidget Widget::cast<TrajectoryWidget>();
         template<> CV_EXPORTS CloudWidget Widget::cast<CloudWidget>();
         template<> CV_EXPORTS CloudNormalsWidget Widget::cast<CloudNormalsWidget>();
         template<> CV_EXPORTS MeshWidget Widget::cast<MeshWidget>();

modules/viz/src/shape_widgets.cpp

@@ -1003,9 +1003,10 @@ cv::viz::CameraPositionWidget::CameraPositionWidget(const Vec2f &fov, double sca
     camera->SetFocalPoint(0.0,0.0,1.0);
     camera->SetClippingRange(0.01, scale);
     
+    double aspect_ratio = tan(fov[0] * 0.5) / tan(fov[1] * 0.5);
+    
     double planesArray[24];
-    // Default aspect ratio = 1.0? fovx/fovy?
-    camera->GetFrustumPlanes(1.0, planesArray);
+    camera->GetFrustumPlanes(aspect_ratio, planesArray);
     
     vtkSmartPointer<vtkPlanes> planes = vtkSmartPointer<vtkPlanes>::New();
     planes->SetFrustumPlanes(planesArray);
@@ -1122,6 +1123,12 @@ cv::viz::CameraPositionWidget::CameraPositionWidget(const Matx33f &K, const Mat
     WidgetAccessor::setProp(*this, actor);
 }
 
+template<> cv::viz::CameraPositionWidget cv::viz::Widget::cast<cv::viz::CameraPositionWidget>()
+{
+    Widget3D widget = this->cast<Widget3D>();
+    return static_cast<CameraPositionWidget&>(widget);
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////////////
 /// trajectory widget implementation
 
@@ -1279,3 +1286,9 @@ cv::viz::TrajectoryWidget::TrajectoryWidget(const std::vector<Affine3f> &path, c
     WidgetAccessor::setProp(*this, actor);
     setColor(color);
 }
+
+template<> cv::viz::TrajectoryWidget cv::viz::Widget::cast<cv::viz::TrajectoryWidget>()
+{
+    Widget3D widget = this->cast<Widget3D>();
+    return static_cast<TrajectoryWidget&>(widget);
+}
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