Flock is a complex Sim World model derived from the “Flocking” model included in the Netlogo model library. This model attempts to mimic the flocking of birds. The flocks in this model are created when each bird follows the same set of rules, instead of having specific “leader” birds (the resulting motion also resembles schools of fish). The agent birds follow three rules: “alignment,” “separation” and “cohesion.” In “alignment,” birds turn so they are moving in the same direction as nearby birds. “Separation” makes birds turn to avoid other birds that get too close. “Cohesion” keeps the flocks together by making birds move towards other nearby birds unless another bird gets too close. When the birds get too close, “separation” overrides the other rules until minimum separation is achieved. Each bird will always move forward at the same constant speed. Play around with the sliders to vary flocking behaviors. The turn sliders control how much a bird can turn as a result of each rule. “Vision” controls how far a bird can see 360 degrees around it. “Speed” controls speed of the birds, and “init size” controls the size of the flock. Finally, “minimum separation” controls how close together birds will get.

Nova Online: Flock (opens a new tab)

Running this model:
1. Click on the “Capture” button in the tool bar.
2. Click “Load” next to “Capture.”
3. Click “Exec” to run the model through multiple iterations. Click “Stop” to stop the graph.
4. To run the model step by step, click “Capture,” “Load,” “Init,” then “Step.” See Wilensky, U. (1998). NetLogo Flocking model. http://ccl.northwestern.edu/netlogo/models/Flocking. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL. flock