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→HOW TO USE IT（使用教程）
有时鸟儿会从鸟群中飞走。这是怎么发生的？为了观察这种现象，您可能需要放慢模型的速度或一步一步地运行它。
有时鸟儿会从鸟群中飞走。这是怎么发生的？为了观察这种现象，您可能需要放慢模型的速度或一步一步地运行它。
== 代码实现 ==
[http://www.netlogoweb.org/launch#http://ccl.northwestern.edu/netlogo/models/models/Sample%20Models/Biology/Flocking.nlogo Netlogo Web - Flocking]<syntaxhighlight line="1">
turtles-own [
flockmates ;; agentset of nearby turtles
nearest-neighbor ;; closest one of our flockmates
]
to setup
clear-all
create-turtles population
[ set color yellow - 2 + random 7 ;; random shades look nice
set size 1.5 ;; easier to see
setxy random-xcor random-ycor
set flockmates no-turtles ]
reset-ticks
end
to go
ask turtles [ flock ]
;; the following line is used to make the turtles
;; animate more smoothly.
repeat 5 [ ask turtles [ fd 0.2 ] display ]
;; for greater efficiency, at the expense of smooth
;; animation, substitute the following line instead:
;; ask turtles [ fd 1 ]
tick
end
to flock ;; turtle procedure
find-flockmates
if any? flockmates
[ find-nearest-neighbor
ifelse distance nearest-neighbor < minimum-separation
[ separate ]
[ align
cohere ] ]
end
to find-flockmates ;; turtle procedure
set flockmates other turtles in-radius vision
end
to find-nearest-neighbor ;; turtle procedure
set nearest-neighbor min-one-of flockmates [distance myself]
end
;;; SEPARATE
to separate ;; turtle procedure
turn-away ([heading] of nearest-neighbor) max-separate-turn
end
;;; ALIGN
to align ;; turtle procedure
turn-towards average-flockmate-heading max-align-turn
end
to-report average-flockmate-heading ;; turtle procedure
;; We can't just average the heading variables here.
;; For example, the average of 1 and 359 should be 0,
;; not 180. So we have to use trigonometry.
let x-component sum [dx] of flockmates
let y-component sum [dy] of flockmates
ifelse x-component = 0 and y-component = 0
[ report heading ]
[ report atan x-component y-component ]
end
;;; COHERE
to cohere ;; turtle procedure
turn-towards average-heading-towards-flockmates max-cohere-turn
end
to-report average-heading-towards-flockmates ;; turtle procedure
;; "towards myself" gives us the heading from the other turtle
;; to me, but we want the heading from me to the other turtle,
;; so we add 180
let x-component mean [sin (towards myself + 180)] of flockmates
let y-component mean [cos (towards myself + 180)] of flockmates
ifelse x-component = 0 and y-component = 0
[ report heading ]
[ report atan x-component y-component ]
end
;;; HELPER PROCEDURES
to turn-towards [new-heading max-turn] ;; turtle procedure
turn-at-most (subtract-headings new-heading heading) max-turn
end
to turn-away [new-heading max-turn] ;; turtle procedure
turn-at-most (subtract-headings heading new-heading) max-turn
end
;; turn right by "turn" degrees (or left if "turn" is negative),
;; but never turn more than "max-turn" degrees
to turn-at-most [turn max-turn] ;; turtle procedure
ifelse abs turn > max-turn
[ ifelse turn > 0
[ rt max-turn ]
[ lt max-turn ] ]
[ rt turn ]
end
; Copyright 1998 Uri Wilensky.
; See Info tab for full copyright and license.
</syntaxhighlight>
== THINGS TO TRY（你可以试一试） ==
== THINGS TO TRY（你可以试一试） ==