%!PS-Adobe-2.0
%%BoundingBox: 0 0 612 792
%%Pages: 1
%%EndComments
%%Page: 1 1

% tewi0.ps - Don Yang (uguu.org)
%
% 11/16/08


% Seed random number generator.
systemdict /Seed known
{
   Seed
}
{
   usertime
}
ifelse srand
9 { rand pop } repeat

% Page settings
/Margin 54 def
/Width 504 def
/Height 684 def
/HalfDiagonal Width dup mul Height dup mul add sqrt 2 div def
/PageScale Width Height lt {Width} {Height} ifelse def
/SpriteSpacing 18 def
/SpriteScale 0.2 def

% Generate random number between 0 and 1
/Rand { rand 2 31 exp div } bind def

% Initialize colors
/Hue Rand def

% Initialize parameters
/StepCount 8 def
/TPhase Rand 360 mul def
/TPeriod Rand 240 mul 120 add PageScale div def

% Draw a single sprite at origin
/Dan
{
   % Bottom layer
   -50 0 moveto
   -33  16  -23  25    0  25 curveto
    23  25   33  16   50   0 curveto
    33 -16   23 -25    0 -25 curveto
   -23 -25  -33 -16  -50   0 curveto
   clip newpath

   Hue 1.0 0.4 sethsbcolor
   -60 60 moveto
   60 60 lineto
   60 -60 lineto
   -60 -60 lineto
   closepath fill
   
   % Gradient
   1 1 StepCount
   {
      StepCount div

      Hue 1.0
      2 index 0.4 mul 0.4 add
      sethsbcolor

      80 mul -60 add 50 moveto
      40 -100 rlineto
      100 0 rlineto
      0 100 rlineto
      closepath fill
   } for

   % Top layer
   0.0 0.0 1.0 sethsbcolor
   false
   {
      % Full shape
      -33 0 moveto
      -25  10  -16  15    0  15 curveto
       16  15   25  10   33   0 curveto
       25 -10   16 -15    0 -15 curveto
      -16 -15  -25 -10  -33   0 curveto
      fill
   }
   {
      % Half shape
      -33 0 moveto
      -25  10  -16  15    0  15 curveto
       16  15   25  10   33   0 curveto
      closepath fill
   } ifelse
} bind def

% Draw circular set of sprites
/TLoop
{
   % r, a
   /a exch def
   /r exch def

   % Start angle
   0
   
   % Get angular step, round up so that it evenly divides into the circle
   360
      360 SpriteSpacing r atan div
      ceiling div

   360
   {
      % i += 30 * sin(r * TPeriod + TPhase)
      r TPeriod mul TPhase add sin 30 mul
      add /i exch def

      gsave

      % x = cos(i) * r + Margin + Width / 2
      i cos r mul
      Margin add Width 2 div add

      % x, y = sin(i) * r + Margin + Height / 2
      i sin r mul
      Margin add Height 2 div add

      % Draw sprite
      translate
      a i add rotate
      SpriteScale SpriteScale scale
      Dan

      grestore
   } for
} bind def

% Draw a series of sprites laid in concentric circles
/RLoop
{
   % Inner radius
   SpriteSpacing

   % Step
   SpriteSpacing

   % Outer radius
   HalfDiagonal
   {
      % Rotate angle
      dup TPeriod mul TPhase add cos 60 mul
      TLoop
   } for
} bind def

% Clip at page margins
Margin Margin moveto
Width 0 rlineto
0 Height rlineto
Width neg 0 rlineto
closepath clip newpath

% Draw sprites
RLoop

showpage
%%EOF