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const
  
escape=4.0;                { escape value }
  
attract=0.0001;            { attractor sensitivity }

const
  
Black        = 0;
   Blue         = 1;
   Green        = 2;
   Cyan         = 3;
   Red          = 4;
   Magenta      = 5;
   Brown        = 6;
   LightGray    = 7;
   DarkGray     = 8;
   LightBlue    = 9;
   LightGreen   =10;
   LightCyan    =11;
   LightRed     =12;
   LightMagenta =13;
   Yellow       =14;
   White        =15;

function GetRGBColor(color:byte):longint;
begin
  case
Color of
   
black : GetRGBColor := RGB(0,0,0);
    blue  : GetRGBColor := RGB(0,0,128);
    green : GetRGBColor := RGB(0,128,0);
    cyan  : GetRGBColor := RGB(0,255,255);
    red   : GetRGBColor := RGB(128,0,0);
    magenta : GetRGBColor := RGB(128,0,128);
    brown : GetRGBColor := RGB(128,128,0);
    lightgray : GetRGBColor := RGB(192,192,192);
    darkgray : GetRGBColor := RGB(128,128,128);
    lightBlue : GetRGBColor := RGB(0,0,255);
    lightGreen : GetRGBColor := RGB(0,255,0);
    lightcyan : GetRGBColor := RGB(0,255,255);
    lightRed : GetRGBColor := RGB(255,0,0);
    lightmagenta : GetRGBColor := RGB(255,0,255);
    yellow: GetRGBColor := RGB(255,255,0);
    white : GetRGBColor := RGB(255,255,255);
  else
   
GetRGBColor := RGB(0,0,255);
  end;
end;

////////////////////////////////////////////////////////////////////////////////

procedure Fall(ABitmap: TBitmap);
{ compute and display cross fractal
  using Michael Barnsley's IFS algorithm.  Then generate
  snow fall by generating many of them.

}
var
  
x, y      : double;        { pixel coordinates }
  
i, j      : integer;       { loop counters}
  
k         : integer;       { row selector }
  
MaxX,
   MaxY      : integer;      { maximum X screen coordinate}
  
d         : array[1..5,1..6] of double; { holds data of IFS attractor }
  
scale     : double;        { random scale factor}
  
xpos,ypos : integer;      { tree position }
  
Rect      : TRect;
   Iterations : integer;
   c   : TColorRef;
   xValue,
   yValue : integer;
begin
 
SetRect(Rect, 0, 0, ABitmap.Width, ABitmap.Height);
  with Rect do
  begin
   
MaxX := right - left;
    MaxY := bottom - top;     { find maximum Y coordinate }
   
if (MaxX=0) or (MaxY=0) then exit;
    MaxX := Max(MaxX,MaxY);
    MaxY := MaxX;

{ initialize IFS data array }

   
d[1,1]:=0.33; d[1,2]:=0; d[1,3]:=0; d[1,4]:=0.33; d[1,5]:=1;  d[1,6]:=1;
    d[2,1]:=0.33; d[2,2]:=0; d[2,3]:=0; d[2,4]:=0.33; d[2,5]:=MaxX; d[2,6]:=1;
    d[3,1]:=0.33; d[3,2]:=0; d[3,3]:=0; d[3,4]:=0.33; d[3,5]:=1;  d[3,6]:=MaxX;
    d[4,1]:=0.33; d[4,2]:=0; d[4,3]:=0; d[4,4]:=0.33; d[4,5]:=MaxX; d[4,6]:=MaxX;
    d[5,1]:=0.33; d[5,2]:=0; d[5,3]:=0; d[5,4]:=0.33; d[5,5]:=MaxX div 2; d[5,6]:=MaxX div 2;

    x := 0;               {set starting coordinates}
   
y := 0;

    iterations := trunc(MaxY * 10);

    for j := 1 to 20 do                      { make 20 snow flakes }
   
begin
     
xpos := random(MaxX) + Left;           { pick flake position }
     
ypos := random(MaxX) + Top;
      scale := (random(5)+1)/50;             { pick flake scale }

     
for i := 1 to 10 do
      begin                                  
{ skip first 10 iterations }
       
k := random(5) + 1;                   { pick random row }
       
x := d[k,1]*x + d[k,2]*y + d[k,5];    { transform coordinates }
       
y := d[k,3]*x + d[k,4]*y + d[k,6];
      end;

      for i := 11 to iterations do
      begin
       
c:= GetRGBColor(random(4)+12);
        k := random(5) + 1;                   { pick random row }
       
x := d[k,1]*x + d[k,2]*y + d[k,5];    { transform coordinates }
       
y := d[k,3]*x + d[k,4]*y + d[k,6];
        xValue := round(scale*x+xpos);
        yValue := round(scale*y+ypos);
        ABitmap.Canvas.Pixels[xValue,yValue] := C;
      end;
    end;
  end;
end;

////////////////////////////////////////////////////////////////////////////////


2004 Jim Valavanis

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