Going Around in Circles       CPS 004.1, 24 July 2002

Now put your animating skills to the test by making any kind of shape move around in a circular path perpetually. You need to modify only the shape's position in order to make it appear to trace out the path of a circle. However, you will need to think carefully about what tiny change, applied repeatedly over time, will make a shape appear to move in a circle. The easiest way to do this is to think about the problem from the shape's perspective, like when you are driving your car around a curve in the road, rather than from a strictly mathematical perspective.

This assignment is meant to familiarize you with the following concepts discussed in class and your reading:

Specifications

You are to write a Java applet that displays three different shapes, e.g., a triangle, a hexagon, and an oval, moving in circles. Each shape moves around its circle differently, e.g., in a different direction, at a different speed, or different diameter. Although they should appear to be behaving differently, you should create only one behavior class that extends GP.Behaviors.Perpetual. In order to do this, your behavior will need to parameterized properly so it can be added to any kind of shape and its creator can control any aspect of its movement.

An example can be seen online here. A worked out example can be seen online here.

Extra Credit

Generalize your circle behavior to trace out the path of any regular shape, given a number of sides and a length for each side. A regular shape is one whose sides are all the same length and whose angles between those sides are the same as well. For example, an equilateral triangle is a three-sided regular shape, a square is a four-sided regular shape, then a pentagon, then a hexagon, and so on. We can approximate a circle on the computer by making a regular shape that has 360 sides, each of length one.

What to Submit

When finished, you and your partner should transfer the entire project folder created by Visual J++ to your respective public_html/cps4 folder in the acpub system and update your course web page to link to the newly transferred project using the guidelines given here.