Построение треугольника Серпинского с помощью рекурсии

unit Unit1; 
 
{$mode objfpc}{$H+}
 
interface
 
uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, StdCtrls,
  ExtCtrls;
 
type
 
  { TForm1 }
 
  TForm1 = class(TForm)
    Button1: TButton;
    PaintBox1: TPaintBox;
    procedure Button1Click(Sender: TObject);
  private
    { private declarations }
    procedure tr(x1, y1, x2, y2, x3, y3: integer);
    procedure draw(x1, y1, x2, y2, x3, y3: Real; n: real);
  public
    { public declarations }
  end; 
 
const
 iter = 6;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.lfm}
 procedure TForm1.tr(x1, y1, x2, y2, x3, y3: integer);
begin
 
         paintbox1.canvas.moveto(x1,y1);
         paintbox1.canvas.lineto(x2,y2);
         paintbox1.canvas.moveto((x2),round(y2));
         paintbox1.canvas.lineto(round(x3),round(y3));
         paintbox1.canvas.moveto(round(x3),round(y3));
         paintbox1.canvas.lineto(round(x1),round(y1));
 
end;
 
 procedure TForm1.draw(x1, y1, x2, y2, x3, y3: Real; n: real);
var
	x1n, y1n, x2n, y2n, x3n, y3n : Real;
 
begin
	if  n > 0  then
	begin
		x1n := (x1 + x2) / 2;
		y1n := (y1 + y2) / 2;
		x2n := (x2 + x3) / 2;
		y2n := (y2 + y3) / 2;
		x3n := (x3 + x1) / 2;
		y3n := (y3 + y1) / 2;
 
		tr(trunc(x1n), trunc(y1n), trunc(x2n), trunc(y2n), trunc(x3n), trunc(y3n));
 
	        draw(x1, y1, x1n, y1n, x3n, y3n, n - 1);
		draw(x2, y2, x1n, y1n, x2n, y2n, n - 1);
		draw(x3, y3, x2n, y2n, x3n, y3n, n - 1);
	end;
end;
 
 
procedure TForm1.Button1Click(Sender: TObject);
begin
tr(320,10,600,470,40,470);
draw(320,10,600,470,40,470,iter);{}
end;
 
end.