;; SUMMARY
globals
[ old-shape
  change-shape?
  frames
]

Turtles-own [ next base-color direction ]

to startup
   setup
end
   
To setup
  Ca
  ;; Assign each turtle to follow the next-highest turtle
  crt pop
  [ set next turtle ( (who + 1) mod pop)
    rt random 360
    jump max-pxcor
    set shape shape-choice
    ;; rainbow colors
    set base-color hsb (255 * who / (pop + 1)) 255 255
    set color base-color
    ]
    tick
End

To go
  if not any? turtles [ setup ]
  if [ shape ] of turtle 0 != shape-choice
  [ ask turtles [ set shape shape-choice ]
  ]
  ifelse scale-with-min-dist?
  [ let new-size min-dist * size-factor
    ask turtles with [ size != new-size ]
    [ set size new-size ]
  ]
  [ let new-size size-factor
    ask turtles with [ size != new-size ]
    [ set size new-size ]
  ]
  ifelse unicolor?
  [ if [color != blue ] of turtle 0      [ ask turtles [ set color blue ] ] ]
  [ if [color != base-color] of turtle 0 [ ask turtles [ set color base-color ] ] ]
  ask turtles
  [ ;; if my next is too close
    ifelse distance-nowrap next <= min-dist
    [ ;; turn towards it, and away a little bit
      face-nowrap next
      rt avoid-heading
      ;; jump
      jump step-size
    ]
    [ ; if not to close, just turn-towards and step-forward
      face-nowrap next 
      jump step-size
    ]
  ]
  tick
End
@#$#@#$#@
GRAPHICS-WINDOW
200
10
720
551
25
25
10.0
1
10
1
1
1
0
1
1
1
-25
25
-25
25
1
1
1
ticks

CC-WINDOW
5
565
729
660
Command Center
0

BUTTON
8
48
63
81
reset
setup
NIL
1
T
OBSERVER
NIL
NIL
NIL
NIL

BUTTON
123
49
178
82
NIL
go
T
1
T
OBSERVER
NIL
NIL
NIL
NIL

SLIDER
8
10
180
43
pop
pop
10
1000
100
10
1
NIL
HORIZONTAL

SLIDER
8
121
181
154
min-dist
min-dist
0.5
2
0.5
0.05
1
NIL
HORIZONTAL

BUTTON
123
85
178
118
scatter
setxy random world-width random world-height
NIL
1
T
TURTLE
NIL
NIL
NIL
NIL

SLIDER
9
191
182
224
avoid-heading
avoid-heading
0
180
90
5
1
degrees
HORIZONTAL

SLIDER
8
156
181
189
step-size
step-size
0
2
0.5
0.05
1
Units
HORIZONTAL

CHOOSER
10
367
148
412
shape-choice
shape-choice
"default" "dotted-vector" "vector" "line" "circle" "circle-2" "box" "box-2" "ant" "chain"
3

SLIDER
9
226
181
259
size-factor
size-factor
0.1
5
1
0.1
1
NIL
HORIZONTAL

SWITCH
10
261
182
294
scale-with-min-dist?
scale-with-min-dist?
1
1
-1000

SWITCH
10
331
116
364
unicolor?
unicolor?
1
1
-1000

BUTTON
9
84
64
117
default
set min-dist .50\nset step-size .50\nset avoid-heading 90\nset size-factor 1.0\nset scale-with-min-dist? false
NIL
1
T
OBSERVER
NIL
NIL
NIL
NIL

@#$#@#$#@
==SUMMARY==

Linked chains follow each other.

==WHAT IS IT?==

A simple model. A chain of linked turtles. They follow each other. That is, each link as a "leader". Each link steps toward its leader, until it is some minimum distance, if the leader is too close, the link steps away at a preset angle.

Use the sliders and switches to vary the rules that are used.

Some interesting effects emerge, especially with many links.

===THE CONTROLS===

|pop| - how many links in the chain. can not be changed during GO. 

|min-dist| - the closest that links want to get
             when 'scale-with-min-dist' is on,
             size-factor is multiplied by this value.

|step-size| - how far a link moves each step
              smaller values make for smoother movement,
              but experiement with larger values too:
              interesting effects emerge.

|avoid-heading| - the angle added to the current heading
                  when the lead is too close

|size-factor| - the base size of the links.

|scale-with-min-dist| - when on, the size is scaled by min-dist.
                        for links that seem to be connected, turn this on,
                        then set size-factor to 2.

|double-correct| - after turning away and stepping forward or backward,
                   turn back by the same amount

|shape-choice| - choose the shape to use for the chain.

different shapes reveal different information about the chain:
* lines show the way angles change
* circle hides the chaning angles, but lets one focus on the chain as a whole.
* dotted-vector accentuates the curvyness of a shape.

|frame-skip| - model skips displaying this many frames. speeds things up,
             can hide complexity for rapidly evolving shapes,
             can use to freeze-frame repeating shapes, and determine the cycles

==THINGS TO LOOK FOR==

when a link wraps across an edge, the result is usually that the follower turns and crosses the screen to get back to it. this can keep a chain system unstable.

* some chain systems will stabilize given enough room and time
* some will shrink/expand into a circle
* some never calm down
* some seem stable for awhile (especially larger chains) then suddenly shift.
* note that often the overall *shape* is fairly stable, even though the individual
* members are racing around and around the perimiter.

==NETLOGO FEATURES==

* Well chosen shapes can expose information.
* Using nodisplay and display to control screen-redrawing
* Storing turtles in a turtle variable creates linked turtles
* turtle scaling strongly affects execution speed.

=== XML Tags ===

<info>
<summary>Linked objects follow each other, endlessly.</summary>
<copy>Copyright (C) 2004,2009 James P. Steiner</copy>
</info>
@#$#@#$#@
default
true
0
Polygon -7500403 true true 150 5 40 250 150 205 260 250

ant
true
0
Polygon -7500403 true true 136 61 129 46 144 30 119 45 124 60 114 82 97 37 132 10 93 36 111 84 127 105 172 105 189 84 208 35 171 11 202 35 204 37 186 82 177 60 180 44 159 32 170 44 165 60
Polygon -7500403 true true 150 95 135 103 139 117 125 149 137 180 135 196 150 204 166 195 161 180 174 150 158 116 164 102
Polygon -7500403 true true 149 186 128 197 114 232 134 270 149 282 166 270 185 232 171 195 149 186
Polygon -7500403 true true 225 66 230 107 159 122 161 127 234 111 236 106
Polygon -7500403 true true 78 58 99 116 139 123 137 128 95 119
Polygon -7500403 true true 48 103 90 147 129 147 130 151 86 151
Polygon -7500403 true true 65 224 92 171 134 160 135 164 95 175
Polygon -7500403 true true 235 222 210 170 163 162 161 166 208 174
Polygon -7500403 true true 249 107 211 147 168 147 168 150 213 150

box
true
0
Polygon -7500403 true true 45 255 255 255 255 45 45 45

box-2
true
0
Rectangle -7500403 true true 75 0 225 150

chain
true
1
Circle -2674135 false true 104 74 92
Circle -2674135 false true 106 -14 88

circle
false
0
Circle -7500403 true true 35 35 230

circle-2
true
0
Circle -7500403 true true 75 0 150

dotted-vector
true
1
Line -2674135 true 150 150 150 -3
Line -2674135 true 148 0 136 30
Line -2674135 true 150 0 165 29
Circle -2674135 true true 136 136 28
Circle -2674135 true true 136 285 28

line
true
1
Line -2674135 true 150 150 150 -3

vector
true
1
Line -2674135 true 150 150 150 -3
Line -2674135 true 148 0 136 30
Line -2674135 true 150 0 165 29
Circle -2674135 true true 136 136 28

@#$#@#$#@
NetLogo 4.0.4
@#$#@#$#@
@#$#@#$#@
@#$#@#$#@
@#$#@#$#@
@#$#@#$#@
default
0.0
-0.2 0 0.0 1.0
0.0 1 1.0 0.0
0.2 0 0.0 1.0
link direction
true
0
Line -7500403 true 150 150 90 180
Line -7500403 true 150 150 210 180

@#$#@#$#@