aUCBLogo Demos and Tests / knots

to knots       ; Knots by Andreas Micheler
   setsc 0
   perspective
   setpc 4
   cs
   ht
   pu
      fd 100
      left 90
      rightRoll 90
      fd 200
      right 90
      leftRoll 90
   pu
   repeat 1000
   [   phi=repcount/1000
      fd 2
      down (2.19+cos (3*360*phi))*360/1000
      rightRoll 1.35*(sin (3*360*phi))*360/1000

;      down 3*360/1000
;      rightRoll 2*(sin (3*360*phi))*360/1000

      setpc hsb 360*phi 1 1
      square
   ]
   erN "square_pos

   rotateScene
end

to square
   ifelse not name? "square_pos
   [   square_width=40
      square_pos=posXYZ

      right 90
      forward square_width

         square_edge=posXYZ

      back square_width
      left 90
   ][
      local [new_pos new_edge]

      new_pos=posXYZ
      pd
         PolyStart
            setPosXYZ PosXYZ
            setPosXYZ square_pos
            setPosXYZ square_edge
         PolyEnd
         pu setPosXYZ new_pos pd
         PolyStart
            setPosXYZ PosXYZ
            setPosXYZ square_edge
            pu setPosXYZ new_pos
            right 90
            pd
            forward square_width
         PolyEnd
      pu
      square_edge=posXYZ
      back square_width
      left 90
      square_pos=new_pos
   ]
end