A NetLogo experiment used for the procedural placement of trees throughout an environment.

forest-gen.nlogo

breed [ trees tree ]

trees-own [ age ]

to setup
  clear-all
  ask patches [ set pcolor brown ]
  set-default-shape trees "tree"
  
  if behaviour = "naive" [ naive-behaviour ]
  if behaviour = "spawnpoints" [ spawnpoints-behaviour ]
  if behaviour = "realistic" [ spawn-trees ]
end

to spawn-trees
  create-trees start-amount-of-trees [
    set age random death-age
    set color green
    set heading random 360
    fd random 300
  ]
end

to realistic-behaviour
  ;- No neighbour must be too close to its other neighbour
  ;- Trees age with time, when they mature they spread their seed
  ;- When they spread their seed, their seed has a variable strength
  ;- When they reach a certain age, they die
  set age age + 1
  
  if age >= mature-age [
    spread-seed
  ]
  
  if age >= death-age [ die ]
  
  check-if-outgrown
  
end

to check-if-outgrown
  let neighbour min-one-of other trees [distance myself]
  
  if distance neighbour < death-radius-threshold [
    if [age] of neighbour > age [
      die
    ]
  ]
  
end

to update-realistic-behaviour
  ask trees [ realistic-behaviour ]
end

to spread-seed
  if random seed-weakness = 1 [
    hatch-trees 1 [
      set age 0
      set heading random 360
      fd random spread-radius 
    ]
  ]
end

to spawnpoints-behaviour 
  create-tree-spawns
   
  ask trees [
    hatch-trees trees-per-spawn [
      set color green
      set heading random 360
      fd random spawn-radius 
    ]
  ]
end

to create-tree-spawns 
  ask trees [ die ]
  
  create-trees spawn-amount [ 
    set heading random 360
    fd random 200
    set color red
  ]
  
end

to naive-behaviour
  ask trees [ die ]
  create-trees tree-amount [
    set heading random 360
    fd random 200
    set color green
  ]
end
@#$#@#$#@
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@#$#@#$#@
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@#$#@#$#@
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@#$#@#$#@
NetLogo 5.0.5
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@#$#@#$#@
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