StarLogo Project:
Circle
WHAT IS IT?
This project shows a new way to create a circle with Logo.
The turtles don't draw a circle. Rather, the turtles
arrange themselves into a circle, based on their
interactions with one another.
Each turtle follows two simple rules: (1) it tries to keep a
certain distance from each of its two "neighbors", (2) it
gently "repels" the group as a whole, trying to move away
from the other turtles. With these two rules, the turtles
arrange themselves into a circle.
HOW TO USE IT
Click the SETUP button to set up the turtles. Click the
ADJUST button, then click the REPEL button.
The NUM slider controls the total number of turtles. The
DESIRED-DISTANCE slider controls the distance that each
turtle tries to keep from its neighbors. The CONVERGENCE
slider controls how quickly the turtles move toward the
desired distance from their neighbors. The REPEL-STRENGTH
slider controls how strongly each turtle tries to move away
from the group as a whole.
THINGS TO NOTICE
When you click on the ADJUST button, the turtles "relax" into
a pattern with each turtle at the desired distance from its
two neighbors. There are many ways for each turtle to be
equidistant from its two neighbors. When you turn on the REPEL
button, the turtles move to a different "solution": a circle.
After the turtles have formed a circle, reduce the
DESIRED-DISTANCE slider and the circle shrinks. Increase the
DESIRED-DISTANCE and the circle expands.
EXPLORATIONS
* Change the SETUP procedure so that the turtles start in
random positions all over the screen (not clustered near the
middle, as in the original SETUP procedure). Then turn on the
ADJUST and REPEL sliders. Do the turtles still form a
circle?
* What happens if you turn on only the REPEL button (and not
the ADJUST button)?
STARLOGO FEATURES
If you kill turtles while certain "forever buttons" are
running, the computer might crash (since the buttons might
refer to turtles that no longer exist). So, in this project,
the SETUP procedure explicitly stops the forever buttons
before killing the turtles (with the CA command).
