Spiral: Proper Fills and Add Arcs on each end
lazarus / 39-Graphics

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Boleeman · 2024-04-09 09:22

Been working on filling some spirals with colors and making their ends
round with arcs (as shown in the attached picture)

Can't seem to get the fill to work just between the red lines with
random colors. Always have  a bigger snail like shape filled on top
that obscures the other spiral sections.

The CSharp Helper site has something similar , but I could not work
out how Mr Stevens did it. His spiral ends all line up.
My spiral ends are radially spaced. Attached is his csharp version
picture. Also, as the form is resized the number of spirals increase
dynamically.

Here is my code so far:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  unit
Unit1; {$mode objfpc}{$H+} interface uses  Classes, SysUtils, Forms,
Controls, Graphics, Dialogs, ExtCtrls, StdCtrls,  Spin; type   {
TForm1 }   TForm1 = class(TForm)    chkDirection: TCheckBox;   
PaintBox1: TPaintBox;    Panel1: TPanel;    seAValue: TSpinEdit;   
seNumSpirals: TSpinEdit;    procedure chkDirectionChange(Sender:
TObject);    procedure PaintBox1Paint(Sender: TObject);    procedure
seAValueChange(Sender: TObject);    procedure
seNumSpiralsChange(Sender: TObject);  private    SpiralBrushes: array
of TBrush;    function Distance(point1, point2: TPoint): Single;   
procedure DrawSpirals(ACanvas: TCanvas; center: TPoint; A: Single;
num_spirals: Integer; rect: TRect);    procedure PolarToCartesian(r,
theta: Single; out x, y: Single);  public   end; var  Form1:
TForm1; implementation {$R *.lfm}  procedure
TForm1.PaintBox1Paint(Sender: TObject);begin 
DrawSpirals(PaintBox1.Canvas, Point(PaintBox1.Width div 2,
PaintBox1.Height div 2), seAValue.Value, seNumSpirals.Value,
PaintBox1.ClientRect);end; procedure TForm1.chkDirectionChange(Sender:
TObject);begin      PaintBox1.Invalidate;end; procedure
TForm1.seAValueChange(Sender: TObject);begin   
PaintBox1.Invalidate;end; procedure TForm1.seNumSpiralsChange(Sender:
TObject);begin    PaintBox1.Invalidate;end; procedure
TForm1.DrawSpirals(ACanvas: TCanvas; center: TPoint; A: Single;
num_spirals: Integer; rect: TRect);var  i: Integer;  d_start,
start_angle, max_dist, max_theta, theta, r, x, y: Single;  points:
array of TPoint;  rectCenter: TPoint;begin  ACanvas.Clear; 
ACanvas.Pen.Color := clBlack;  ACanvas.Brush.Style := bsClear;  
d_start := 2 * Pi / num_spirals;  start_angle := 0;  max_theta :=
max_dist / A + 2 * Pi;   SetLength(points, 0);  for i := 1 to
num_spirals do  begin    theta := 0;    SetLength(points, 0);    while
theta <= max_theta do    begin      r := A * theta;     
PolarToCartesian(r, theta + start_angle, x, y);      x += center.X;  
  y := center.Y + y;      SetLength(points, Length(points) + 1);     
points[High(points)] := Point(Trunc(x), Trunc(y));      theta += Pi /
36; // 5 degrees    end;    ACanvas.Pen.Color := clRed; // Set pen
color to red for curved spiral lines    ACanvas.Polyline(points); //
Draw radial lines    start_angle += d_start;     ACanvas.Pen.Color :=
clBlue; // Set pen color to blue    ACanvas.MoveTo(Round(center.X +
(points[High(points)].X - center.X) * (num_spirals - 1) /
num_spirals), Round(center.Y + (points[High(points)].Y - center.Y) *
(num_spirals - 1) / num_spirals)); // Move pen to three-quarters of
the distance from the center to the end of the radial line   
ACanvas.LineTo(points[High(points)].X, points[High(points)].Y); //
Draw line to end of the radial line  end;end; function
TForm1.Distance(point1, point2: TPoint): Single;var  dx, dy:
Single;begin  dx := point1.X - point2.X;  dy := point1.Y - point2.Y; 
Result := Sqrt(dx * dx + dy * dy);end; procedure
TForm1.PolarToCartesian(r, theta: Single; out x, y: Single);begin  x
:= r * Cos(theta);  y := r * Sin(theta);end; end.  end.