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

% udonge0.ps - Don Yang (uguu.org)
%
% 11/14/08


% Seed random number generator.  Use a seed defined from command line
% if available, otherwise use usertime.  An external seed is
% preferred, since PostScript built-ins like usertime and realtime are
% fairly deterministic.
systemdict /Seed known
{
   Seed
}
{
   usertime
}
ifelse srand

% Due to PostScript implementation, the first few random numbers tend
% to be not so random (they tend to be small numbers), so throw them
% away until we get enough randomness.
9 { rand pop } repeat

% Page settings
/Margin 54 def
/Width 504 def
/Height 684 def
/PageScale Width Height lt {Width} {Height} ifelse def
/SpriteSpacing 20 def
/SpriteScale 0.08 def

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

% Initialize colors for HSB gradient.  The colors here are chosen more
% for psychedelic effect than for aesthetic reasons.  Brightness is not
% 1.0 to make the shapes more visible on white paper.
/Hue1 0.7 Rand 0.3 mul sub def
/Hue2 1.0 Rand 0.3 mul sub def
/Brightness 0.6 def

% Initialize parameters
/StepCount 8 def
/XPhase Rand 360 mul def
/YPhase Rand 360 mul def
/XPeriod Rand 240 mul 120 add PageScale div def
/YPeriod Rand 240 mul 120 add PageScale div def

% Draw a single sprite at origin
/Zayaku
{
   % Clipping path.  Drawing all shapes with some overlap then
   % trimming it later with a clip avoids numerical artefacts (e.g.
   % thin color lines at shape boundaries)
   -100 50 moveto
   40 50 lineto
   100 0 lineto
   40 -50 lineto
   -100 -50 lineto
   closepath clip newpath

   % Bottom layers
   Hue1 1.0 Brightness sethsbcolor
   -110 60 moveto
   0 60 lineto
   0 -60 lineto
   -110 -60 lineto
   closepath fill

   Hue2 1.0 Brightness sethsbcolor
   0 60 moveto
   110 60 lineto
   110 -60 lineto
   0 -60 lineto
   closepath fill

   % Gradient.  This can be implemented with shfill instead, but it's
   % more straightforward to do it manually, especially for
   % interpolating across HSB space.  Avoiding shfill also means we
   % can stay at LanguageLevel 2.
   1 1 StepCount
   {
      StepCount div
      dup Hue2 Hue1 sub mul Hue1 add 1.0 Brightness sethsbcolor

      100 mul -80 add dup
      60 moveto
      100 60 rlineto
      0 -120 rlineto
      -60 lineto
      closepath fill
   } for

   % Top layer.  Only half of the shape is drawn by default, since
   % that looks better when printed on white paper.
   false
   {
      % Full center shape
      0.0 0.0 1.0 sethsbcolor
      -85 35 moveto
      30 35 lineto
      70 0 lineto
      30 -35 lineto
      -85 -35 lineto
      closepath fill
   }
   {
      % Half center shape
      0.0 0.0 1.0 sethsbcolor
      -85 35 moveto
      30 35 lineto
      70 0 lineto
      -85 0 lineto
      closepath fill
   }
   ifelse
} bind def

% Draw one row of sprites
/XLoop
{
   % y, sy
   /sy exch def
   /y exch def

   0 SpriteSpacing Width
   {
      % x, sx = sin((x + XPhase) * XPeriod)
      dup
      XPhase add XPeriod mul sin

      % x, angle = 360 * ((sx + sy + 2) / 4)
      sy add 2 add 4 div 360 mul

      % Draw sprite
      gsave
      exch y translate
      Margin Margin translate
      rotate
      SpriteScale SpriteScale scale
      Zayaku
      grestore
   } for
} bind def

% Draw rows of sprites
/YLoop
{
   0 SpriteSpacing Height
   {
      % y, sy = sin((y + YPhase) * YPeriod)
      dup
      YPhase add YPeriod mul sin
      XLoop
   } for
} bind def

YLoop
showpage
%%EOF