Assignment 5: Tracker ball

Due: 9:00am, Monday, February 22. Value: 30 pts. Submit to Sauron.

In class we saw a simple program that displays a red ball using the graphics package.

from graphics import *

center = Point(100, 100)  # create a red ball at (100, 100)
ball = Circle(center, 20)
ball.setFill('red')

win = GraphWin('Ball')    # create a window
ball.draw(win)            # and put the ball inside it

loc = win.getMouse()      # wait for click, get location of mouse

You will need to install the graphics package in order to complete this assignment. To do this, right-click graphics.py, select Save Link As… or Save Target As… from the pop-up menu, and save the file on your computer. Then start a new file in the Wing IDE, copy the above code, and save it in the same directory where you placed the graphics.py file. If the above code doesn't work, contact the instructor.

Your assignment is to modify the above program so that when the user clicks the mouse, the ball moves toward the location of the click, at a rate of one pixel for every 0.05 seconds. It should do this for 5 mouse clicks.

To move toward the click, you'll want to compute the distance between the ball's center and the click's location using the distance formula:

You will want the animation to last dist frames. (Of course, dist isn't an integer, but you can use the int function to round it down to the correct number of frames.) With each step of the animation, you will want to move the ball (x₁ − x₀) / dist pixels in the x-direction and (y₁ − y₀) / dist pixels in the y-direction.

First write and test your program to handle just one click, and then modify it so that after reaching the destination on one click, your program waits for another click and then moves the ball toward it. Overall, your program should handle 5 mouse clicks. (Of course, you should implement this using a for loop rather than copying the code five times!) You'll likely find that a click is not effective until the ball completes moving to the last click's location; that's fine.

Recall that you can retrieve the x-coordinate of a point (such as loc) using its getX method: loc.getX(). Similarly, getY gives a point's y-coordinate. Recall also that you can get a point object representing the circle's center using its getCenter method: ball.getCenter(). This gives you a point, which you can then ask for an x- and y-coordinate using that point's getX and getY methods.