// I've combined a skin-textured triangle over a
// shaded/curved boarder.  Then flat cubes are
// sprinkled over the top for the appearance of a
// full spacial scene.

set bb 198621
set mm 98621
set seed <time 4>
number random range
{
   set bl (seed*bb+1)
   set seed (bl % mm)
   value (seed % range)
}

number abs abs_value
{
   smaller? 0 abs_value
   {
      value abs_value
   }
   notsmaller? 0 abs_value
   {
      value (-abs_value)
   }
}

command draw_sub_tri x1 y1 c1 x2 y2 c2 x3 y3 c3 level maxlevel
{
   set mx ((x1+x2+x3)/3)
   set my ((y1+y2+y3)/3)
   set mc ((c1+c2+c3)/3)
   smaller? 0 level
   {
      draw_sub_tri x1 y1 c1 x2 y2 c2 mx my mc (level-1) maxlevel
      draw_sub_tri x2 y2 c2 x3 y3 c3 mx my mc (level-1) maxlevel
      draw_sub_tri x3 y3 c3 x1 y1 c1 mx my mc (level-1) maxlevel
   }
   pen (level*100/maxlevel)
   line mx my x1 y1
   line mx my x2 y2
   line mx my x3 y3
}

command draw_tri x1 y1 z1 x2 y2 z2 x3 y3 z3 levels
{
   draw_sub_tri x1 y1 z1 x2 y2 z2 x3 y3 z3 levels levels
   line x1 y1 x2 y2
   line x2 y2 x3 y3
   line x3 y3 x1 y1
}

command back_gradient
{
   repeat a 0 100
   {
      pen a
      line a 0 0 (100-a)
      line a 100 100 (100-a)
   }
}

command draw_solid_tri x1 y1 x2 y2 x3 y3
{
   set len ((<abs (x2-x1)>+<abs (y2-y1)>)/3)
   smaller? 0 len
   {
      repeat cnt 0 len
      {
         line x3 y3 (x1+(x2-x1)*cnt/len) (y1+(y2-y1)*cnt/len)
      }
   }
}

command draw_solid_rect x1 y1 x2 y2 x3 y3 x4 y4
{
   draw_solid_tri x1 y1 x2 y2 x4 y4
   draw_solid_tri x2 y2 x3 y3 x4 y4
}

command set_x pntnum value
{
   set <array (pntnum*3+1)> value
}
command set_y pntnum value
{
   set <array (pntnum*3+2)> value
}
command set_z pntnum value
{
   set <array (pntnum*3+3)> value
}
number get_x pntnum
{
   value <array (pntnum*3+1)>
}
number get_y pntnum
{
   value <array (pntnum*3+2)>
}
number get_z pntnum
{
   value <array (pntnum*3+3)>
}

command unit_cube
{
   repeat cz 0 1
   {
      repeat cy 0 1
      {
         repeat cx 0 1
         {
            set_x ((((cz*2)+cy)*2)+cx) (cx*2-1)
            set_y ((((cz*2)+cy)*2)+cx) (cy*2-1)
            set_z ((((cz*2)+cy)*2)+cx) (cz*2-1)
         }
      }
   }
}
command move_cube tx ty tz
{
   repeat pntnum 0 7
   {
      set_x pntnum (<get_x pntnum>+tx)
      set_y pntnum (<get_y pntnum>+ty)
      set_z pntnum (<get_z pntnum>+tz)
   }
}

command scale_cube sx sy sz
{
   repeat pntnum 0 7
   {
      set_x pntnum (<get_x pntnum>*sx)
      set_y pntnum (<get_y pntnum>*sy)
      set_z pntnum (<get_z pntnum>*sz)
   }
}

command rotate_cube_5 rx ry rz
{
   set numbase 10000
   set sin5  872
   set cos5  9962
   smaller? 0 rx
   {
      set sinx (sin5)
      set cosx (cos5)
      set rx (rx-5)
   }
   smaller? rx 0
   {
      set sinx (-sin5)
      set cosx (cos5)
      set rx (rx+5)
   }
   same? 0 rx
   {
      set sinx 0
      set cosx numbase
   }
   smaller? 0 ry
   {
      set siny (sin5)
      set cosy (cos5)
      set ry (ry-5)
   }
   smaller? ry 0
   {
      set siny (-sin5)
      set cosy (cos5)
      set ry (ry+5)
   }
   same? 0 ry
   {
      set siny 0
      set cosy numbase
   }
   smaller? 0 rz
   {
      set sinz (sin5)
      set cosz (cos5)
      set rz (rz-5)
   }
   smaller? rz 0
   {
      set sinz (-sin5)
      set cosz (cos5)
      set rz (rz+5)
   }
   same? 0 rz
   {
      set sinz 0
      set cosz numbase
   }

   repeat pntnum 0 7
   {
      set x <get_x pntnum>
      set y <get_y pntnum>
      set z <get_z pntnum>
      set x2 ((x*cosz-y*sinz)/numbase)
      set y ((y*cosz+x*sinz)/numbase)
      set x ((x2*cosy-z*siny)/numbase)
      set z ((z*cosy+x2*siny)/numbase)
      set_x pntnum x
      set_y pntnum y
      set_z pntnum z
   }
   notsmaller? <abs rx> 5
   {
      rotate_cube_5 rx ry rz
   }
   smaller? <abs rx> 0
   {
      set rx 0
      notsmaller? <abs ry> 0
      {
         rotate_cube_5 rx ry rz
      }
      smaller? <abs ry> 0
      {
         set ry 0
         notsmaller? <abs rz> 0
         {
            rotate_cube_5 rx ry rz
         }
      }
   }
}

command draw_cube
{
   draw_solid_rect <get_x 0> <get_y 0> <get_x 1> <get_y 1> <get_x 3> <get_y 3> <get_x 2> <get_y 2>
   draw_solid_rect <get_x 4> <get_y 4> <get_x 5> <get_y 5> <get_x 7> <get_y 7> <get_x 6> <get_y 6>
   draw_solid_rect <get_x 0> <get_y 0> <get_x 1> <get_y 1> <get_x 5> <get_y 5> <get_x 4> <get_y 4>
   draw_solid_rect <get_x 2> <get_y 2> <get_x 3> <get_y 3> <get_x 7> <get_y 7> <get_x 6> <get_y 6>
   draw_solid_rect <get_x 1> <get_y 1> <get_x 3> <get_y 3> <get_x 7> <get_y 7> <get_x 5> <get_y 5>
   draw_solid_rect <get_x 0> <get_y 0> <get_x 2> <get_y 2> <get_x 6> <get_y 6> <get_x 4> <get_y 4>
}

command render_cube centerx centery centerz radius xang yang zang
{
   unit_cube
   scale_cube radius radius radius
   rotate_cube_5 xang yang zang
   move_cube centerx centery centerz
   draw_cube
}

paper 100
antialias 1

repeat cube_num 1 20
{
   pen <random 100>
   render_cube (<random 80>+10) (<random 80>+10) (<random 80>+10) (10+<random 25>) <random 50> <random 50> <random 50>
}
back_gradient
draw_tri 25 25 70 80 90 10 -50 100 0 5