Autumn

breed [leaves leaf]
breed [dead-leaves dead-leaf]
breed [raindrops raindrop]
breed [suns sun]

leaves-own [
  water-level       ;; amount of water in the leaf
  sugar-level       ;; amount of sugar in the leaf
  attachedness      ;; how attached the leaf is to the tree
  chlorophyll       ;; level of chemical making the leaf green
  carotene          ;; level of chemical making the leaf yellow
  anthocyanin       ;; level of chemical making the leaf red
]

raindrops-own [
  location          ;; either "falling", "in root", "in trunk", or "in leaves"
  amount-of-water
]

globals [
  bottom-line        ;; controls where the ground is
  evaporation-temp   ;; temperature at which water evaporates
]

;; ---------------------------------------
;; setup
;; ---------------------------------------

to setup
  clear-all
  set bottom-line min-pycor + 1
  set evaporation-temp 30
  set-default-shape raindrops "circle"
  set-default-shape suns "circle"

  ;; Create sky and grass
  ask patches
    [ set pcolor blue - 2 ]
  ask patches with [pycor < min-pycor + 2]
    [ set pcolor green ]

  ;; Create leaves
  create-leaves number-of-leaves [
    set chlorophyll 50 + random 50
    set water-level 75 + random 25
    ;; the sugar level is drawn from a normal distribution based on user inputs
    set sugar-level random-normal start-sugar-mean start-sugar-stddev
    set carotene random 100
    change-color
    set attachedness 100 + random 50
    ;; using sqrt in the next command makes the turtles be
    ;; evenly distributed; if we just said "fd random-float 10"
    ;; there'd be more turtles near the center of the tree,
    ;; which would look funny
    fd sqrt random-float 100
  ]

  ;; Create trunk and branches
  ask patches with [pxcor = 0 and pycor <= 5 or
                    abs pxcor = (pycor + 2) and pycor < 4 or
                    abs pxcor = (pycor + 8) and pycor < 3]
    [ set pcolor brown ]

  ;; Create the sun
  create-suns 1 [
    setxy max-pxcor - 2
          max-pycor - 3
    ;; change appearance based on intensity
    show-intensity
  ]

  ;; plot the initial state
  reset-ticks
end 


;; ---------------------------------------
;; go
;; ---------------------------------------

to go
  ;; Stop if all of the leaves are dead
  if not any? leaves [ stop ]

  ;; Have the wind blow and rain fall;
  ;; move any water in the sky, on the ground, and in the tree;
  ;; set the appearance of the sun on the basis of its intensity.
  make-wind-blow
  make-rain-fall
  move-water
  ask suns [ show-intensity ]

  ;; Now our leaves respond accordingly
  ask attached-leaves
  [
    adjust-water
    adjust-chlorophyll
    adjust-sugar
    change-color
    change-shape
  ]

  ;; if the leaves are falling keep falling
  ask leaves [ fall-if-necessary ]

  ;; Leaves on the bottom should be killed off
  ask leaves with [ycor <= bottom-line]
    [ set breed dead-leaves ]

  ;; Leaves without water should also be killed off
  ask leaves with [water-level < 1]
    [ set attachedness 0 ]

  ;; Make sure that values remain between 0 - 100
  ask leaves [
    if chlorophyll < 0 [ set chlorophyll 0 ]
    if chlorophyll > 100 [ set chlorophyll 100 ]
    if water-level < 0 [ set water-level 0 ]
    if water-level > 100 [ set water-level 100 ]
    if sugar-level < 0 [ set sugar-level 0 ]
    if sugar-level > 100 [ set sugar-level 100 ]
    if carotene < 0 [ set carotene 0 ]
    if carotene > 100 [ set carotene 100 ]
    if anthocyanin < 0 [ set anthocyanin 0 ]
    if anthocyanin > 100 [ set anthocyanin 100 ]
    if attachedness < 0 [ set attachedness 0 ]
    if attachedness > 100 [ set attachedness 100 ]
  ]

  ;; increment the tick counter
  tick
end 


;; ---------------------------------------
;; make-wind-blow: When the wind blows,
;; the leaves move around a little bit
;; (for a nice visual effect), and
;; reduce their attachedness by the wind factor.
;; This means that leaves will fall off more
;; rapidly in stronger winds.
;; ---------------------------------------

to make-wind-blow
  ask leaves [ ifelse random 2 = 1
                 [ rt 10 * wind-factor ]
                 [ lt 10 * wind-factor ]
               set attachedness attachedness - wind-factor
             ]
end 


;; ---------------------------------------
;; make-rain-fall: rain is a separate breed
;; of small turtles that come from the top of the world.
;; ---------------------------------------

to make-rain-fall
  ;; Create new raindrops at the top of the world
  create-raindrops rain-intensity [
    setxy random-xcor max-pycor
    set heading 180
    fd 0.5 - random-float 1.0
    set size .3
    set color gray
    set location "falling"
    set amount-of-water 10
  ]
  ;; Now move all the raindrops, including
  ;; the ones we just created.
  ask raindrops [ fd random-float 2 ]
end 


;; --------------------------------------------------------
;; move-water: water goes from raindrops -> ground,
;; ground -> trunk/branches, and trunk/branches to leaves.
;; --------------------------------------------------------

to move-water

  ;; We assume that the roots extend under the entire grassy area; rain flows through
  ;; the roots to the trunk
  ask raindrops with [location = "falling" and pcolor = green] [
    set location "in roots"
    face patch 0 ycor
  ]

  ;; Water flows from the trunk up to the central part of the tree.
  ask raindrops with [location = "in roots" and pcolor = brown] [
    face patch 0 0
    set location "in trunk"
  ]

  ;; Water flows out from the trunk to the leaves.  We're not going to
  ;; simulate branches here in a serious way
  ask raindrops with [location = "in trunk" and patch-here = patch 0 0] [
    set location "in leaves"
    set heading random 360
  ]

  ;; if the raindrop is in the leaves and there is nothing left disappear
  ask raindrops with [location = "in leaves" and amount-of-water <= 0.5] [
    die
  ]

  ;; if the raindrops are in the trunk or leaves and they are at a place
  ;; where they can no longer flow into a leaf then disappear
  ask raindrops with [
    (location = "in trunk" or location = "in leaves")
     and (ycor > max [ycor] of leaves or
          xcor > max [xcor] of leaves or
          xcor < min [xcor] of leaves) ] [
    die
  ]
end 

;;---------------------------------------------------------
;; Turtle Procedures
;; --------------------------------------------------------

;; --------------------------------------------------------
;; show-intensity: Change how the sun looks to indicate
;; intensity of sunshine.
;; --------------------------------------------------------

to show-intensity  ;; sun procedure
  set color scale-color yellow sun-intensity 0 150
  set size sun-intensity / 10
  set label word sun-intensity "%"
  ifelse sun-intensity < 50
    [ set label-color yellow ]
    [ set label-color black  ]
end 

;; --------------------------------------------------------
;; adjust-water: Handle the ups and downs of water within the leaf
;; --------------------------------------------------------

to adjust-water
  ;; Below a certain temperature, the leaf does not absorb
  ;; water any more.  Instead, it converts sugar and and water
  ;; to anthocyanin, in a proportion
  if temperature < 10 [ stop  ]

  ;; If there is a raindrop near this leaf with some water
  ;; left in it, then absorb some of that water
  let nearby-raindrops raindrops in-radius 2 with [location = "in leaves" and amount-of-water >= 0]

  if any? nearby-raindrops [
    let my-raindrop min-one-of nearby-raindrops [distance myself]
    set water-level water-level + ([amount-of-water] of my-raindrop * 0.20)
    ask my-raindrop [
      set amount-of-water (amount-of-water * 0.80)
    ]
  ]

  ;; Reduce the water according to the temperature
  if temperature > evaporation-temp
    [ set water-level water-level - (0.5 * (temperature - evaporation-temp)) ]

  ;; If the water level goes too low, reduce the attachedness
  if water-level < 25
    [ set attachedness attachedness - 1 ]
end 


;; ---------------------------------------
;; adjust-chlorophyll: It's not easy being green.
;; Chlorophyll gets reduces when the temperature is
;; low, or when the sun is strong.  It increases when
;; the temperature is normal and the sun is shining.
;; ---------------------------------------

to adjust-chlorophyll

  ;; If the temperature is low, then reduce the chlorophyll
  if temperature < 15
    [ set chlorophyll chlorophyll - (.5 * (15 - temperature)) ]

  ;; If the sun is strong, then reduce the chlorophyll
  if sun-intensity > 75
    [ set chlorophyll chlorophyll - (.5 * (sun-intensity - 75)) ]

  ;; New chlorophyll comes from water and sunlight
  if temperature > 15 and sun-intensity > 20
    [ set chlorophyll chlorophyll + 1 ]
end 


;; ---------------------------------------
;; adjust-sugar: water + sunlight + chlorophyll = sugar
;; ---------------------------------------

to adjust-sugar
  ;; If there is enough water and sunlight, reduce the chlorophyll
  ;; and water, and increase the sugar
  if water-level > 1 and sun-intensity > 20 and chlorophyll > 1
    [ set water-level water-level - 0.5
      set chlorophyll chlorophyll - 0.5
      set sugar-level sugar-level + 1
      set attachedness attachedness + 5
    ]

  ;; Every tick of the clock, we reduce the sugar by 1
  set sugar-level sugar-level - 0.5
end 

;; ---------------------------------------
;; fall-if-necessary:  If a leaf is above the bottom row, make it fall down
;; If it hits the bottom line, make it a dead-leaf
;; ---------------------------------------

to fall-if-necessary
  if attachedness > 0 [ stop ]
  if ycor > bottom-line
    [
      let target-xcor (xcor + random-float wind-factor
                            - random-float wind-factor)
      facexy target-xcor bottom-line
      fd random-float (.7 * max (list wind-factor .5))
     ]
end 


;; ---------------------------------------
;; change-color: Because NetLogo has a limited color scheme,
;; we need very simple rules
;; ---------------------------------------

to change-color
  ;; If the temperature is low, then we turn the
  ;; sugar into anthocyanin
  if temperature < 20 and sugar-level > 0 and water-level > 0
    [ set sugar-level sugar-level - 1
      set water-level water-level - 1
      set anthocyanin anthocyanin + 1 ]

  ;; If we have more than 50 percent chlorophyll, then
  ;; we are green, and scale the color accordingly
  ifelse chlorophyll > 50
       [ set color scale-color green chlorophyll 150 -50 ]

  ;; If we are lower than 50 percent chlorophyll, then
  ;; we have yellow (according to the carotene), red (according
  ;; to the anthocyanin), or orange (if they are about equal).

       ;; If we have roughly equal anthocyanin and carotene,
       ;; then the leaves should be in orange.
       [ if abs (anthocyanin - carotene ) < 10
           [ set color scale-color orange carotene 150 -50 ]

         if anthocyanin > carotene + 10
           [ set color scale-color red anthocyanin 170 -50 ]

         if carotene > anthocyanin + 10
           [ set color scale-color yellow carotene 150 -50 ]
       ]
end 

to change-shape
  ifelse leaf-display-mode = "solid"
    [ set shape "default" ]
  [ if leaf-display-mode = "chlorophyll"
      [ set-shape-for-value chlorophyll ]
    if leaf-display-mode = "water"
      [ set-shape-for-value water-level ]
    if leaf-display-mode = "sugar"
      [ set-shape-for-value sugar-level ]
    if leaf-display-mode = "carotene"
      [ set-shape-for-value carotene ]
    if leaf-display-mode = "anthocyanin"
      [ set-shape-for-value anthocyanin ]
    if leaf-display-mode = "attachedness"
      [ set-shape-for-value attachedness ]
  ]
end 

;; returns all leaves still attached

to-report attached-leaves
  report leaves with [attachedness > 0]
end 

;; makes the leaf appear to be more or less filled depending on value

to set-shape-for-value [value]
  ifelse value > 75 [ set shape "default" ]
  [ ifelse value <= 25 [ set shape "default one-quarter" ]
    [ ifelse value <= 50 [ set shape "default half" ]
                         [ set shape "default three-quarter" ]]]
end 


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