Lab 7: Flying Rocks

Turning in your work

Late penalties: 1 day late: -5%, 2 days: -10%, -3 days: -20%.

To turn your work in, go to mycourses.unh.edu, find CS414, open the syllabus, and click on Lab 7. Then click Submit Assignment, click Choose file, and find rocks.py.

Your task:

Run Idle, and then open the file rocks.py. Choose "Run -> Run Module" to see the program in action. You may have to move your code windows to the right, to see the turtle window.

Then, complete these steps:

1. The rock's initial motion is to the right. This is set in initialize_rocks(), with a seven-number list: [x,y, vx,vy, angle, rotation_rate, size]. Change that line to modify the rock's vy:

                rock_motion = [0,0, 30,20, 0, 0, 20]
              

   The rock should now move up, and to the right.

2. Now, make the rock turn, by changing its rotation rate to 100 degrees/second:

                rock_motion = [0,0, 30,20, 0, 100, 20]
              

3. Notice the random_motion function. It generates some random numbers for the rock's motion:

                x = random.randrange(window_left, window_right)
                y = random.randrange(window_bottom, window_top)
                vx = random.random() * 200 - 100
                vy = random.random() * 200 - 100
                rotation_rate = random.random() * 200 - 100
              

   use it by replacing the rock_motion = line with this:

                rock_motion = random_motion()
              

   Now, run the program again. If you don't see anything, the rock might have moved off-screen; run it again.

4. Make the rock bigger. This will happen in several places:
   • in random_motion, replace the return line:

                      return [x, y, vx, vy, 0, rotation_rate, 100]
                    

   • in draw_rock, change the forward() amounts. Replace 20 with size .

5. if the rock exist the right side window, make it reappear on the left side, and if it exits the left side, make it appear on the right. change the code thus:
   • In move_rocks(t) add this line at the end:

                    wrap_around(rock_motion)
                  

   • You will now have to implement wrap_around(motion). Enter this code in that function:

                    x = motion[0]
                    y = motion[1]
                    if x > window_right:
                        motion[0] = window_left
                    if x < window_left:
                         motion[0] = window_right
                    

     Add two more if-statements, to handle the top and bottom. Note: if the rock seems to get stuck on one side, make sure you're doing the > and < comparisons correctly.

6. Create another rock. You will need to change several parts of the code:
   • At the top, create another motion record:

                      rock2_motion = []
                    

   • In initialize_rocks(), you will need to declare rock2_motion global, and add a line to give it a random motion.
   • In move_rocks, you'll have to add two lines to move rock 2, and to wrap it around.
   • In draw_rocks, you'll have to add another line to draw rock 2.

7. Give both rocks a random size, between 20 and 120 pixels. In random_motion, call random.randrange(20,120), and put its result as the last value in the returned list (it's currently 20).

8. Make the rocks bounce, if they collide: in move_objects(T), add this code at the bottom:

                x1   = rock_motion[0]
                y1   = rock_motion[1]
                rad1 = rock_motion[6]
                x2   = rock2_motion[0]
                y2   = rock2_motion[1]
                rad2 = rock2_motion[6]
                if collided(x1,y1,rad1, x2,y2,rad2):
                    resolve_collision(rock_motion, rock2_motion, T)
              

9. (10% bonus): Add more rocks. MAKE A COPY OF YOUR rocks.py FIRST, in case this bonus effort doesn't work.

   Instead of having 2 rock motion records, create a list with 5 of them. This will have several consequences in the code:

   • Instead of rock_motion and rock2_motion, there will be a rock_motions list.
   • You will need a loop, to append to this list in initialize_rocks.
   • You will need a loop, to move every rock, in move_rocks .
   • You will need a loop, to draw every rock, in draw_rocks .
   • You will need a double loop in move_objects, to check every rock against every other rock, for collisions, something like this:
     
     

                        for rock1 in rock_motions:
                            for rock2 in rock_motions:
                                if rock1 != rock2:
                                    x1 = rock1[0]
                                    x2 = ...
                                    ...
                                    rad2 = ...
                                    if collided(...):
                                        resolve_collision(...)