По классам: прямая линия в пространстве, её обход

unit Unit4;
 
interface
 
uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, GrObjectClasses, Vcl.ExtCtrls,
  Vcl.StdCtrls, Vcl.ComCtrls;
 
type
  TForm4 = class(TForm)
    pb1: TPaintBox;
    tb1: TTrackBar;
    procedure FormCreate(Sender: TObject);
    procedure pb1Paint(Sender: TObject);
    procedure tb1Change(Sender: TObject);
  private
    procedure InitializeActions;
    procedure DrawObject(p: TGrObject);
    procedure DrawLine(L: TLine);
  public
    procedure DrawAll();
  end;
 
var
  Form4: TForm4;
 
implementation
 
{$R *.dfm}
 
procedure TForm4.InitializeActions();
var
  Line: TLine;
begin
  Line := TLine.Create;
  Line.StartPoint:=Point3(10, 50, 4);
  Line.EndPoint:=Point3(70, 20, 2);
  GrObjects.Add(Line);
 
  Line := TLine.Create;
  Line.StartPoint:=Point3(100, 5, 4);
  Line.EndPoint:=Point3(7, 140, 5);
  GrObjects.Add(Line);
 
  Line := TLine.Create;
  Line.StartPoint:=Point3(13, 190, 5.1);
  Line.EndPoint:=Point3(77, 25, 0.54);
  GrObjects.Add(Line);
end;
 
 
procedure TForm4.pb1Paint(Sender: TObject);
begin
  pb1.Canvas.Brush.Color := clBlack;
  pb1.Canvas.FrameRect(pb1.ClientRect);
  DrawAll;
end;
 
procedure TForm4.tb1Change(Sender: TObject);
begin
  GrObjects.Scale := tb1.Position /100;
  pb1.Invalidate;
end;
 
procedure TForm4.DrawLine(L:TLine);
var p1,p2:TPoint;
begin
  p1:=GrObjects.GetCrd(l.StartPoint);
  p2:=GrObjects.GetCrd(l.EndPoint);
  pb1.Canvas.MoveTo(p1.X,p1.y);
  pb1.Canvas.LineTo(p2.X,p2.y);
end;
 
procedure TForm4.DrawObject(p:TGrObject);
begin
  if p is TLine then
    DrawLine(p as TLine);
end;
 
procedure TForm4.DrawAll;
var
  i: Integer;
begin
  for i := 0 to GrObjects.Count-1 do
    DrawObject(GrObjects[i]);
end;
 
procedure TForm4.FormCreate(Sender: TObject);
begin
  InitializeActions;
end;
 
end.

unit GrObjectClasses;
 
interface
uses
 
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ComCtrls, StdCtrls, ExtCtrls, Contnrs;
type
 
  TPoint3 = record
    X: single;
    Y: single;
    Z: single;
  end;
 
  TGrObject=class
   Function Execute():boolean; virtual; abstract;
  end;
 
  TLine = class(TGrObject)
    StartPoint: TPoint3;
    EndPoint: TPoint3;
    Function Execute():boolean; override;
  end;
 
  TGrObjects=class(TObjectList)
  private
    function GetItems(index: integer): TGrObject;
    procedure SetItems(index: integer; const Value: TGrObject);
  public
    Scale : single;
    function GetCrd(P:TPoint3):TPoint;
    function Add(obj:TGrObject):Integer;
    procedure Remove(obj:TGrObject);
    procedure Execute();
    property Items[index:integer]:TGrObject read GetItems write SetItems; default;
    constructor Create(AOwnsObjects:boolean);
  end;
 
var
  GrObjects:TGrObjects;
 
function Point3(a,b,c:single):TPoint3;
 
implementation
 
function Point3(a,b,c:single):TPoint3;
begin
  Result.X:=a;
  Result.Y:=b;
  Result.Z:=c;
end;
 
 
function TLine.Execute():boolean;
begin
// без понятия что тут
end;
 
 
{ TGrObjects }
function TGrObjects.Add(obj: TGrObject): Integer;
begin
  result := inherited add(obj);
end;
 
 
constructor TGrObjects.Create(AOwnsObjects: boolean);
begin
  inherited Create(AOwnsObjects);
  scale:=1;
end;
 
procedure TGrObjects.Execute;
var
  i: Integer;
begin
  for i := 0 to Count-1 do
    Items[i].Execute;
end;
 
function TGrObjects.GetCrd(P:TPoint3): TPoint;
begin
  // здесь рассчитываются координаты проекции
  result := point(Round(p.X*Scale), Round(p.Y*Scale));
end;
 
function TGrObjects.GetItems(index: integer): TGrObject;
begin
  result := inherited Items[index] as TGrObject;
end;
 
procedure TGrObjects.Remove(obj: TGrObject);
begin
  inherited Remove(obj);
end;
 
procedure TGrObjects.SetItems(index: integer; const Value: TGrObject);
begin
  inherited Items[index] := Value;
end;
 
initialization
  GrObjects:=TGrObjects.Create(true);
finalization
  GrObjects.Free;
  GrObjects:=NIL;
end.