Q&A - Question

Do it as below:

interface
uses
  ..., GisViewerWnd, GisTypes3D ;

type
  TfrmMain = class(TForm)
    ...
    GIS: TGIS_ViewerWnd ;
    ...
    procedure btn2D3DSwitch( Sender : TObject ) ;
    end;

procedure TfrmMain.btn2D3DSwitch( Sender : TObject ) ;
var
   bp : TGIS_Viewer3DBasePlane ;
begin
   if GIS.IsEmpty then exit ;              // do nothing if no layer is open
   GIS.View3D := not GIS.View3D ;   // change viewer 2D-3D mode
   if GIS.View3D then begin              // if viewer is in 3D mode
     GIS.Viewer3D.ScaleZ := 5.0 ;     // set ScaleZ to 500%

     bp := GIS.Viewer3D.BasePlane ; // get current BasePlane
     bp.Active := False ;                    // disable BasePlane
     GIS.Viewer3D.BasePlane := bp ; // apply settings

     GIS.Viewer3D.DemWalls := TGIS_Viewer3DDemWall.Invisible ;

     //GIS.InvalidateWholeMap ;         // apply changes, not obligatory in this case
  end;
end;