knerr cs21 notes...

back to schedule

WEEK04: computer graphics, using objects
 M: getX() and getY(), color, using sleep for animations

LAB4: due next week
QUIZ 2 today!


- start with my program:

cp /home/jk/inclass/

- now modify it to move the circle to wherever the user
  clicks the mouse. see if you can move it 4 times, then
  close the window.

here's how to get a circle's center x and y locations:

 cp = circ.getCenter()
 cx = cp.getX()
 cy = cp.getY()

and here's how to get a user-mouse-click point:

 newpt = win.getMouse()
 newx = newpt.getX()
 newy = newpt.getY()

COLOR...rgb = red green blue:

- try using the color_rgb function!

>>> c = Circle(p,100)
>>> c.draw(w)
>>> color = color_rgb(0,0,0)       # black
>>> c.setFill(color)
>>> color = color_rgb(0,0,255)     # blue
>>> c.setFill(color)
>>> color = color_rgb(0,255,0)     # green
>>> c.setFill(color)
>>> color = color_rgb(0,255,145)
>>> c.setFill(color)


this simple animation doesn't look very good:

>>> from graphics import *
>>> w = GraphWin("hello",600,600)
>>> p = Point(100,300)
>>> c = Circle(p,50)
>>> c.draw(w)
>>> c.setFill("blue")
>>> c.move(5,0)
>>> for i in range(200):
...   c.move(1,0)

try adding the sleep command to slow down the animation:

>>> from time import sleep
>>> for i in range(200):
...   c.move(1,0)
...   sleep(0.05)

** see if you can write these programs:

  - start with a circle, then ask the user to click
      somewhere in the window, then animate the circle
      to where the user clicked

    NOTE: there are two ways to try this:

       1. wherever they click, use a fixed number of steps
          (e.g., 10) to get from where the circle is to where
          the user clicked

       2. wherever they click, use a fixed amount to move and
          calculate the total steps needed based on the distance
          from the current circle to where the user clicked
  - start with a circle and animate it's motion in one direction.
    if the circle gets to the edge of the graphics window, make
    the circle start moving in the opposite direction.

  - same as the last one, but allow motion in both the x and y directions! :)