Noche estrellada

unit potencial;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;

type
     Carga = record
     x,y : integer;
     q : double;
end;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
     Form1: TForm1;
     Carregues : array [0..50] of Carga;
//     Carregues : array [0..10] of Carga;
//     Carregues : array [0..1] of Carga;

implementation

{$R *.DFM}

function R(x1,y1,x2,y2 : integer): double;
begin
     result := sqrt ((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
end;

function V(x,y : integer; q : Carga) : double; overload;
const
     K : double = $01;
//   K : double = $0100;
begin
     try
     result := q.q*K / R(q.x,q.y,x,y);
     except
     result := 0;
     end;
end;

function V(x,y : integer; q : array of Carga) : double; overload;
var
     i : integer;
begin
     result := 0;
     for i := Low(q) to High(q) do
     result := result + V(x,y,q[i]);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
     i,j : integer;
     col : TColor;
const
     Colors    : array [boolean] of TColor = (clYellow, $80FF00);
begin
     for i := Low(Carregues) to High(Carregues) do
     begin
          Carregues[i].x := random(width);
          Carregues[i].y := random(Height);
          repeat
          Carregues[i].q := (random(2)-1)*random(5)/(random(2) + 0.01);
//          Carregues[i].q := (random(2)-1)*random(2)/(random(2) + 0.01);
          until Carregues[i].q <> 0;
     end;

     canvas.Brush.Color := clBlack;
     canvas.FillRect(Rect(0,0,ClientWidth,ClientHeight));
     canvas.Brush.Color := clRed;

//     col := random($010101);
//     col := 3872;
//     col := 53762;
//   col := 616;
//     col := $010000;
     col := $010101;
//     col := $01;
//     col := $010000;


     for i := 0 to ClientWidth do
     for j := 0 to ClientHeight do
          canvas.Pixels[i,j] := Col*Abs(Round(V(i,j,Carregues)));

     for i := low(Carregues) to High(Carregues) do
          canvas.Pixels[Carregues[i].x,Carregues[i].y] := Colors[Carregues[i].q > 0];

     tag := col;
end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
     Caption := inttostr(Tag) + ' ' + FormatFloat('0.00000',V(X,Y,Carregues));
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
     randomize;
end;

end.