Fire (evolved version)

globals [
  initial-trees
  burned-trees
  ;; how many trees (green patches) we started with
]
breed [fires fire]    ;; bright red turtles -- the leading edge of the fire
breed [embers ember]

to setup
  clear-all
  ;; make some green trees
  ask patches with [(random-float 100) < Density]
    [ set pcolor green ]
    ;; make a column of burning trees at the left-edge
    if Starting_point_of_fire = "Center"  [ask patches [
    if pxcor = 0 and pycor < 5 and pycor > 1
    [ set pcolor red ]
  ]
  ]
  if Starting_point_of_fire = "Left side" [ask patches with [pxcor = min-pxcor]
    [ set pcolor red ]]
  ;; keep track of how many trees there are
  set initial-trees count patches with [pcolor = green]
  reset-ticks
end 

to go
  ;; stop the model when done
  if all? patches [pcolor != red]
      [ stop ]


  ;; each burning tree (red patch) checks its 4 neighbors.
  ;; If any are unburned trees (green patches), change their probability
  ;; of igniting based on the wind direction
  ask patches with [pcolor = red] [
    ;; ask the unburned trees neighboring the burning tree
    ask neighbors4 with [pcolor = green] [
      let probability Propability_of_spread

      ;; compute the direction from you (the green tree) to the burning tree
      ;; (NOTE: “myself” is the burning tree (the red patch) that asked you
      ;; to execute commands)
      let direction towards myself

      ;; the burning tree is north of you
      ;; so the south wind impedes the fire spreading to you
      ;; so reduce the probability of spread
      if (direction = 0 ) [
        set probability probability - South_wind_speed ]

      ;; the burning tree is east of you
      ;; so the west wind impedes the fire spreading to you
      ;; so reduce the probability of spread
      if (direction = 90 ) [
        set probability probability - West_wind_speed ]

      ;; the burning tree is south of you
      ;; so the south wind aids the fire spreading to you
      ;; so increase the probability of spread
      if (direction = 180 ) [
        set probability probability + South_wind_speed ]

      ;; the burning tree is west of you
      ;; so the west wind aids the fire spreading to you
      ;; so increase the probability of spread
      if (direction = 270 ) [
        set probability probability + West_wind_speed ]
      if random 100 < probability [
        set pcolor red ;; to catch on fire
        ;; if big jumps is on, then sparks can fly farther
        if Low_humidity_rates [
          let target patch-at (West_wind_speed / 5) (South_wind_speed / 5)
          if target != nobody and [ pcolor ] of target = green [
            ask target [
              set pcolor red ;; to ignite the target patch
            ]
          ]
        ]
      ]
    ]
    set pcolor red - 3.5;; once the tree is burned, darken its color
  ]

  tick   ;; advance the clock by one “tick”
end 

to Spread_fire_with_mouse
  if mouse-down? [
    ask patch mouse-xcor mouse-ycor [
  set pcolor red
    ]
    display
  ]
end 

; Copyright 2006 Uri Wilensky.
; See Info tab for full copyright and license.