internal static HelixToolkit.Wpf.Ray3D Point2DToRay3D(this Viewport3DX viewport, System.Windows.Point point2d)
{
var r = viewport.Point2DToRay(point2d.ToVector2());
return(new HelixToolkit.Wpf.Ray3D(r.Position.ToPoint3D(), r.Direction.ToVector3D()));
}