private void Viewport3D_ContextMenuOpening(object sender, ContextMenuEventArgs e)
{
Point location = Mouse.GetPosition(viewport);
HitTestResult hit = VisualTreeHelper.HitTest(viewport, location);
var meshHit = hit as RayMeshGeometry3DHitTestResult;
var sphere = spheres.Where(s => s.Geometry.Equals(meshHit.ModelHit)).FirstOrDefault();
if (sphere == null) // if Model3D object weren't touched
{
e.Handled = true;
}
else
{
SelectedSphere = sphere;
}
}