这是一个在恒定力场(例如,靠近地球表面的重力场)中弹跳的球。侧壁和地板是弹跳表面。您可以使用箭头键添加额外的力:
unit Unit5;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, ExtCtrls;
type
TRealVect = record
X, Y: real;
end;
const
ZeroVect: TRealVect = (X: 0; Y: 0);
type
TForm5 = class(TForm)
Timer1: TTimer;
procedure FormPaint(Sender: TObject);
procedure Timer1Timer(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure FormKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
procedure FormKeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
private
{ Private declarations }
function ACC: TRealVect;
const
RADIUS = 16;
DAMPING = 0.8;
DT = 0.2;
GRAVITY: TRealVect = (X: 0; Y: 10);
var
FForce: TRealVect;
FPos: TRealVect;
FVel: TRealVect;
public
{ Public declarations }
end;
var
Form5: TForm5;
implementation
{$R *.dfm}
function RealVect(X, Y: real): TRealVect;
begin
result.X := X;
result.Y := Y;
end;
function Add(A, B: TRealVect): TRealVect;
begin
result.X := A.X + B.X;
result.Y := A.Y + B.Y;
end;
function Scale(A: TRealVect; C: real): TRealVect;
begin
result.X := C*A.X;
result.Y := C*A.Y;
end;
function TForm5.ACC: TRealVect;
begin
result := Add(GRAVITY, FForce);
end;
procedure TForm5.FormCreate(Sender: TObject);
begin
FPos := RealVect(Width div 2, 10);
FVel := RealVect(0, 0);
end;
procedure TForm5.FormKeyDown(Sender: TObject; var Key: Word;
Shift: TShiftState);
begin
case Key of
VK_UP:
FForce := RealVect(0, -20);
VK_DOWN:
FForce := RealVect(0, 10);
VK_RIGHT:
FForce := RealVect(10, 0);
VK_LEFT:
FForce := RealVect(-10, 0);
end;
end;
procedure TForm5.FormKeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
FForce := ZeroVect;
end;
procedure TForm5.FormPaint(Sender: TObject);
begin
Canvas.Brush.Color := clRed;
Canvas.Ellipse(round(FPos.X - RADIUS), round(FPos.Y - RADIUS),
round(FPos.X + RADIUS), round(FPos.Y + RADIUS));
end;
procedure TForm5.Timer1Timer(Sender: TObject);
begin
FVel := Add(FVel, Scale(ACC, DT));
FPos := Add(FPos, Scale(FVel, DT));
if FPos.Y + RADIUS >= ClientHeight then
begin
FVel.Y := -DAMPING*FVel.Y;
FPos.Y := ClientHeight - RADIUS - 1;
end;
if FPos.X - RADIUS <= 0 then
begin
FVel.X := -DAMPING*FVel.X;
FPos.X := RADIUS + 1;
end;
if FPos.X + RADIUS >= ClientWidth then
begin
FVel.X := -DAMPING*FVel.X;
FPos.X := ClientWidth - RADIUS - 1;
end;
Invalidate;
end;
end.
将计时器的时间间隔设置30
为“通常”。
编译示例EXE