private void btn_Add_Arc_Click(object sender, RoutedEventArgs e)
 {
     if (helix3dsim.bCurveSelected)
     {
         helix3dsim.bCurveSelected = false;
         Helix3dSim.makeArc(helix3dsim.nCurveSelected, false);
     }
 }
        //public HelixPoint mouseSelectionStartPoint = new HelixPoint();
        //public HelixPoint mouseSelectionEndPoint = new HelixPoint();
        //protected Point3D? MouseDownPoint3D { get; set; }

        private void Initialize3DSimulator()
        {
            helix3dsim = new Helix3dSim(this);

            show_ctrl_chk.IsChecked   = true;
            link_handle_chk.IsChecked = false;
            btn_Add_Arc.IsEnabled     = false;
            btn_Add_Linear.IsEnabled  = false;

            btn_sim_PointPrevious.IsEnabled      = false;
            btn_sim_PointNext.IsEnabled          = false;
            btn_sim_PointFirst.IsEnabled         = false;
            btn_sim_PointLast.IsEnabled          = false;
            btn_Calculate.IsEnabled              = false;
            btn_sim_player_PlayForward.IsEnabled = false;
            btn_sim_player_PlayReverse.IsEnabled = false;
            btn_sim_player_StepForward.IsEnabled = false;
            btn_sim_player_StepReverse.IsEnabled = false;
            btn_sim_player_Pause.IsEnabled       = false;
            btn_sim_player_Stop.IsEnabled        = false;
            btn_save.IsEnabled                    = false;
            btn_reset.IsEnabled                   = false;
            tb_sim_player_StepSize.Text           = "1";
            lbl_sim_player_CurrentPlayPos.Content = FormatTimeString(0);
            tb_sim_duration.Text                  = FormatTimeString(5);
            //tb_sim_duration.Text = FormatTimeString(MotionGraph.Duration);
            tb_sim_selpoint_x.Text = "0";
            tb_sim_selpoint_y.Text = "0";
            tb_sim_selpoint_z.Text = "0";
            slider_sim_player_TimeSlider.Minimum = 0;
            slider_sim_player_TimeSlider.Maximum = 100;

            prevJointAngles[0] = slider_simPos_J1.Value;
            prevJointAngles[1] = slider_simPos_J2.Value;
            prevJointAngles[2] = slider_simPos_J3.Value;
            prevJointAngles[3] = slider_simPos_J4.Value;
            prevJointAngles[4] = slider_simPos_J5.Value;
            prevJointAngles[5] = slider_simPos_J6.Value;
        }