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Help me solve a Spiral programming dilemma!

Posted on 1998-01-31
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Last Modified: 2010-04-04
I have a small program to write. But when I said that I would do it, it seemed a lot simplier that it does now.

I have to make a program that displays something which I can only label as an "Hypnotic disc"-like spiral. You know, the kind of 2 colors spirals that start on a single point in the center and expand, and when you rotate it, it seem to "go-in" or "go-out" (depending if you rotate it clockwise or counter-clockwise)

Now, using delphi I really don't know how to do it! It must be full screen, have 2 spirals, one red, and one blue. the background must be black.

and the hard part is that it must rotate!! can anyone help? should I use DirectX? is there a way to switch to a 320x200 screen mode from within delphi??

i'm really at a loss. Thanks for ANY help!

(and if such a small program exists, please point me in that direction!!)
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Question by:efortier
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ronit051397 earned 60 total points
ID: 1358074
This source from Lloyd's help file creates two spirals in a metafile file. You can then load the metafile and see what it does. This code was tested on Delphi 1. Hope it will help.



CONST W = 1000; H = 500; R2 = 353;

procedure TForm1.Button1Click(Sender: TObject);

VAR CDC : hDC;

  procedure spiral(CV: TCanvas; Colr: TColor; AngInc: Double;
    RInc: Integer; Sgn1, Sgn2: Integer);
  VAR Theta: Double;
  begin
    Sgn1 := Sgn1 DIV Abs(Sgn1);
    Sgn2 := Sgn2 DIV Abs(Sgn2);
    CV.pen.Color := Colr;
    Theta := 0;
    CV.MoveTo(H,H);
    WHILE Theta < pred(H DIV RInc) DO
      BEGIN
        Theta := Theta + AngInc;
        CV.LineTo(H+Sgn1*Round(RInc*Theta*Cos(Sgn2*Theta)),
                  H+Sgn1*Round(RInc*Theta*Sin(Sgn2*Theta)));
      END;
  end;

begin
  DeleteFile('EXAMPLE.WMF');
  WITH TBitmap.Create DO
    try
      CDC := CreateMetafile(NIL);
      Canvas.Handle := CDC;
      SetMapMode(Canvas.Handle, MM_ANISOTROPIC);
      SetWindowExt(Canvas.Handle, W, W);
      WITH Canvas DO
        BEGIN
          {==== replace with your own image-creation code ===}
          Brush.Color := clWhite;
          pen.Width := 10;
          pen.Style := psInsideFrame;
          pen.Color := clBlack;
          Ellipse(0,0,W,W);
          Spiral(Canvas, clRed, pi/4, 18, 1, 1);
          Spiral(Canvas, clBlue, pi/4, 18, -1, 1);

          Pen.Color := clBlack;
          PolyLine([Point(H,0), Point(H,H), Point(H-R2, H+R2),
            Point(H,H), Point(H,W), Point(H,H),
            Point(H+R2,H+R2)]);
          {====== end image-creation code =====}
        END;
      WITH TMetafile.Create DO
        try
          Handle := CloseMetafile(CDC);
          Inch   := W;
          Height := 128;
          Width  := 128;
          SaveToFile('EXAMPLE.WMF');
        finally
          Free;
        end;
    finally

      Free;
    end;
end;

{ This code came from Lloyd's help file! }
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