Optical Illusions

globals [caption]

;; runs automatically when model is opened

to startup
  set caption ""  ;; otherwise it would start out as 0
end 

to illusion-1
  clear-all
  set caption "What color are the circles?"
  set-default-shape turtles "circle"
  ;; make the gray lines
  ask patches with [pxcor mod 5 = 0 or
                    pycor mod 5 = 0]
    [ set pcolor gray ]
  ;; make the circles
  ask patches with [pxcor mod 5 = 0 and
                    pycor mod 5 = 0]
    [ sprout 1
        [ set color white
          set size 1.7 ] ]
end 

to illusion-2
  clear-all
  set caption "Are the thick lines parallel?"
  ask patches
    [ set pcolor white ]
  ;; make 2 parallel lines
  ask patches with [abs pycor = 4]
    [ set pcolor black ]
  ;; make diagonal lines that start at the center
  ;; and go to different parts of the world
  crt 60
    [ set heading who * 6
      set color black
      set shape "line"
      set size 100 ]
  ;; make a circle in the center
  crt 1
    [ set color black
      set shape "circle"
      set size 5 ]
end 

to illusion-3
  clear-all
  set caption "Are the lines parallel?"
  set-default-shape turtles "square"
  ask patches
    [ set pcolor gray ]
  ;; every fourth patch creates a square, either black or white
  ask patches with [pxcor mod 4 = 0 and
                    pycor mod 4 = 0]
    [ sprout 1
        [ set heading 0
          set size 4.8
          ifelse pxcor mod 8 = 0
            [ set color white ]
            [ set color black ] ] ]
  ;; move every other row over 1 to the right
  ask turtles with [pycor mod 16 = 4]
    [ set xcor xcor + 1 ]
  ;; move every other row over 1 to the left
  ask turtles with [pycor mod 16 = 12 ]
    [ set xcor xcor - 1 ]
end 

to illusion-4
  clear-all
  set caption "Which inner circle is bigger?"
  set-default-shape turtles "circle"

  ;; make right figure
  let counter 0
  ask patch -12 0
    [ ;; middle circle
      sprout 1
        [ set color white
          set size 5
          ;; 6 smaller circles around the middle circle
          hatch 6
            [ set size 2.5
              set heading 60 * counter
              fd 4
              set counter counter + 1 ] ] ]
  ;; make left figure
  set counter 0
  ask patch 6 0
    [ ;; middle circle
      sprout 1
        [ set color white
          set size 5
          ;; 6 larger circles around the middle circle
          hatch 6
            [ set size 8
              set heading 60 * counter
              fd 8
              set counter counter + 1 ] ] ]
end 

to illusion-5
  clear-all
  set caption "Stare at the dot, then lean forward and back."
  ask patches
    [ set pcolor gray ]
  ;; make the inside circle of diamonds
  ;; use ordered turtles so the circle is evenly spaced
  create-ordered-turtles 32
    [ set size 2
      set shape "diamond1"
      fd 12 ]
  ;; make the outside circle of diamonds
  ;; use ordered turtles so the circle is evenly spaced
  create-ordered-turtles 40
    [ set size 2
      set shape "diamond2"
      fd 15 ]
  ;; make the dot in the middle
  crt 1
    [ set shape "circle"
      set color black ]
end 

to illusion-6
  clear-all
  set caption "Feeling queasy?"
  ask patches [
    ;; use RGB colors since ordinary NetLogo colors aren't neon enough
    set pcolor one-of [[30 58 190] [133 10 166]]
    ;; place turtles only on patches where both coordinates are even
    if pxcor mod 2 = 0 and pycor mod 2 = 0 [
      sprout 1 [
        set color [99 187 64]
        set shape "lozenge"
        __set-line-thickness 0.15
        set size 2
        ;; make repeating "wave" pattern of headings
        set heading ((pxcor + pycor) / 3) mod 6 * 30
      ]
    ]
  ]
end 

to illusion-7
  clear-all
  set caption "Spirals or circles?"
  ask patches [ set pcolor gray ]
  set-default-shape turtles "square 3"
  cro 16 [ fd  4 rt 15 ]
  cro 32 [ fd  8 lt 15 ]
  cro 46 [ fd 12 rt 15 ]
  cro 60 [ fd 16 lt 15 ]
  ask turtles [
    set size 1.7
    ifelse who mod 2 = 0
    [ set color black ]
    [ set color white ]
  ]
end 


; Copyright 2005 Uri Wilensky.
; See Info tab for full copyright and license.