Lab 3

Part 1 - Introduction to Programming in Alice

A. - Moving a ball

1. Start Alice
2. Click Cancel on the pop up screen
3. Under the File tab, select New world
4. Select the grass template and click Open
5. Click Add Objects
6. In the Sports gallery select the toyBall1, add the Ball to the scene, Select Done
7. In the Object Tree click on toyBall1 (upper left)
8. In the Details panel (lower left), drag and drop toyBall1 move into the Method editor (world.my first method area). In the pop-up window select right > 1 meter.
9. In the Toolbar click Play.
10. Notice that the Ball moves to the left and back on the screen. Close the screen.
11. We need to change the direction of the movement so that the Ball moves forward and to the left of the screen. In the Method editor, find the line starting with toyBall1 move... Click the drop down arrow to the right of right and select forward. Replay the scene.
12. Repeat the above step to add a second toyBall1 move forward statement to the editor.
13. We only want the Ball to move forward 0.8 meters in the second statement. Select 1 meter > and click other. A number pad will pop-up, select .8 and click okay.
14. Play the scene.
15. Notice the jerky movement of the Ball.

B. - Moving a ball with style

1. In the first statement, select the more dropdown arrow. Two of the options available are duration and style.
   • duration controls the speed of the movement; a shorter time gives a faster movement.
   • style controls how the Ball moves
     • gently will start the movement gently and accelerate and then decelerate to a gentle stop (gentle at both ends),
     • abruptly will move at a constant speed
     • begin gently begins gentle and ends abrupt
     • end gently begins abruptly and ends gentle.
   • Try selecting different styles for the first statement and observe the effect.
2. Select style = begin gently for statement 1 and style = end gently for statement 2. Click Play and notice the smooth overall movement.
3. SAVE YOUR WORK:
   • Under the File tab select Save world.
   • In the look in box use the dropdown arrow and find the Z: drive (this is your network drive associated with your CS department account.)
   • Use Lab3-1 as the file name. Click save.

C. On your own - When balls collide

1. Add a second toyBall to the scene so that the first Ball "hits" the new Ball at the end of its movement. The new Ball moves away from the "impact".
2. You will need to be careful of your placement of the 2nd Ball so that it can be hit by the first Ball. The best way to do this is to use the methods to place the Ball as talked about in Lab 1. You also need to think of the movement styles of the 2 Balls.
3. Placement hint:
   • Add the new Ball to the scene.
   • Use the move-to method of the new Ball to place the Ball over the old Ball.
   • Use the move method to move the new Ball forward 1.80 meters plus a little more for the radius of the Balls (move-to and move use the center of the Ball to measure distance).
4. SAVE YOUR WORK!

Part 2 - Primitive Method Exploration / Class-Level Custom Methods

A. Custom Methods, Methods of the Monkey

1. Under the File tab, select New world. Save the new world as Lab3-2.
2. Select the grass template and click Open
3. Click Add Objects
4. In the Sports gallery select the toyBall1, add the Ball to the scene.
5. In the Animals gallery select the class Monkey, add a Monkey to the scene. Place the Monkey sort of near the Ball and facing away from the Ball.
6. Select Done
7. Examine the Monkey Class-level Custom methods: In the Object Tree click Monkey
8. In the Details panel notice the five methods that are listed above the create new method box. These are Class-level custom methods for the Monkey class. Take a few minutes to drag and drop the methods into the Method editor and press play to see what they do. (You will need earphones to hear the screech sound).

B. Primitive methods, The Monkey turns

• Delete the statements from the editor.
• Scene:
  1. The monkey turns around 360 degrees (1 revolution)
  2. The monkey says, "I think I'll play with that ball"
  3. Monkey turns to ball, moves closer and kicks the ball.
  4. The ball moves forward in an arc.

1. In the Object Tree click Monkey
2. In the Details panel drag and drop Monkey turn into the Method editor.
3. In the pop-up window select right > 1 revolution.
4. Select the Monkey say method, select other, and type in the string I think I'll play with that ball.
5. Select the monkey turn to face method and select toyBall1
6. Select the move to method and select toyBall1.
7. Press Play.
8. Notice the monkey is now IN the ball. Close the play screen
9. Delete the last statement.
10. Select move toward > 1/4 meter > toyBall1
11. In the editor, in the last statement, select the dropdown arrow next to amount=0.25 meters and select other. Enter a distance to move towards the ball. If you do not know the correct distance try a number, press play to see what it does and repeat till the monkey is close enough to kick the ball.
12. Save your work. Press play.

C. The Monkey kicks

Monkey kicks the ball. To do this you will have to manipulate the monkey's leg to perform a smooth kicking motion.

1. In the Object Tree expand the monkey object (click the + sign next to monkey)
2. Select the leftLeg object
3. Drag the leftLeg turn method to the editor, select turn > forward .25 revolutions
4. In tree, expand leftLeg object, select lowerLeg object
5. Drag the lowerLeg turn method to the editor, select turn > forward .25 revolutions
6. Select leftLeg Object, drag the leftLeg turn method to the editor, select turn > backward .25 revolutions
7. Select lowerLeg object, drag the lowerLeg turn method to the editor, select turn > backward .5 revolutions
8. Press play.
   • Notice that the leg movement is not smooth. We need some way to move the upper and lower legs at the same time.
9. Across the bottom of the editor are 7 control structures. These can control the flow of your program. The 2nd from the left is the Do together structure. Program statements are performed sequentially. Do together allows you to perform two statements at the same time in a block. The block is treated as a sequential statement by Alice.
10. Drag Do together into the editor and place it above the first leftLeg turn statement (a green line will indicate where the statement will be placed).
11. Drag the leftLeg turn forward and the lowerLeg turn forward statements into the Do together block.
12. With a 2nd Do together block repeat the same steps for the turn backward statements.
13. Add a statement to return the lower leg to a standing position after the kick.
14. Press play to verify your code.

D. Own your on - The ball flies

• After the monkey kicks the ball the ball will fly in an arc (sort of) away from the monkey. To get the ball to arc you need to move the ball up and forward at the same time and then down and forward at the same time.
• Add statements and control blocks to move the ball forward in a 1 meter high arc a distance of 2 meters.
• Press Play.

• Change the styles so that the up-forward movement is faster than the down.
• Make sure that the durations inside a Do together block match. What happens if they don't?
• Play with changing the up style - leave the forward style as before.
• I ended with the up-forward durations being .5 seconds and the down-forward being 1 second (the default).

• The current program has the monkey ending his kick (back to standing) before the ball moves. Change this by moving the last statement of the Monkey kick (line 12 above) into the ball's up-forward Do together block. Try it first with the default duration of 1 second for the leg movement (the duration for the ball movements should be .5 seconds).
• Notice the ball pauses in flight? Why?
• Change the leg movement duration to .5 seconds.
• Play and save your work.
• For fun you can add a monkey screech when the monkey kicks the ball. Be careful, at present you have no way of controlling the duration of the screech statement. You could also do a little more to make the ball move when the monkey's foot is touching the ball. This would require more statements and a little experimentation with the timing.

Part 3 - Breaking an animation into scenes using world methods

Note: These are world methods NOT Class-level custom methods.

What we have now is an animation of a monkey kicking a ball. It is written as one long series of statements. We can break this animation down into 3 subparts; monkey turns to face ball, monkey kicks ball, and the ball flies through the air or monkeyTurns, monkeyKicks, and ballFlies. These subparts can be called modules. We can break our program into modules by dividing the code into methods to be called by the main world method. The best way to do this is as you are writing your program. We did not do this so we will have to break our program into modules using copy and paste.

• Select Edit > Preferences from the top menu.
• Change the number of clipboards to 5.
• Click okay. You should now have 5 clipboard icons in the upper right corner of the screen.
• Save as a new file. Select File > save world as from the top menu.
• Save the file as Lab3-3.

1. In the Object tree select world.
2. In details panel select create new method.
3. Enter monkeyTurns and click okay.
4. Repeat step 2 to create the monkeyKicks and ballFlies methods.
5. In the editor you should now have 4 tabs with the world.my first method, world.monkeyTurns, world.monkeyKicks, and world.ballFlies methods.
6. Select my first method.
7. Starting at the first statement, drag the statement to the first clipboard. Drag the next statement to the 2nd clipboard. Repeat this process for the statements that have the monkey turn, turn to face the ball, and move to the ball.
8. Select the world.monkeyTurns tab in the editor.
9. Select the first clipboard and drag it into the editor. The First statement should appear in the window. Repeat for the other statements.
10. Select my first method. Delete the statements you just pasted into the monkeyTurns method. In the editor right click on the statement and select delete. Or drag the statement into the garbage can at the top of the screen.
11. Repeat this process for the statements that make up the monkey kicking action and the ball fling action.
12. You're my first method should now be empty. If you press play nothing will happen. All of your code still exists, it exists in methods. A method must be called for its code to be executed. Let's do this now.
13. From the Tree select world. From Details drag the monkeyTurns method into the editor.
14. Press play.
15. From the Tree select world. From Details drag the monkeyKicks method into the editor.
16. Press play.
17. From the Tree select world. From Details drag the ballFlies method into the editor.
18. Now you have the complete animation in 3 modules. Press play.

You may ask, "In step 12 you said that a method had to be called to be executed. What is calling my first method?" Good question.

If you look in the Events area of the Alice screen (to the right of the animation window) you will see the line When world starts do followed by my first method.

• Using the dropdown arrow try changing this to ballFlies. Press play.
• You will notice that just the statements in the ballFlies method are executed. The monkey should be left standing with his left leg in an awkward position. Change the Event back to my first method.
• SAVE YOUR WORK!

Part 4 - Putting it all together exercise -The Monkey Scores

• Create a new world saved as Lab3-4.
• Create an animation of the scene described below.
• The code should be modularized into appropriate modules and use good naming conventions for the methods.
• You can refactor (reuse) some of the code from the previous exercise.

• Setup:
  • On a grass field a monkey stands near a ball.
  • A few meters from the monkey there is a soccer goal with the open side towards the monkey.
  • Standing in front of the goal is a man playing goalie. He is standing in the normal position of a goalie between the goal and the ball and the monkey.
  • So, you scene should be in this order. The monkey facing towards goal, ball, a little space, goalie facing towards monkey, goal with open end towards goalie.
• Action:
  • The monkey takes 2 steps towards the ball and kicks the ball.
  • The ball flies in an arc towards one side of the goal.
  • The goalie jumps/dives and reaches to block the ball from getting onto the goal.
  • The ball sores past the goalie's hands.
  • The ball lands in the goal.
  • The goalie lays on his side where he fell in defeat.
  • The monkey screeches a victory screech.
• More action:
  • The goalie gets up. The goalie picks up the ball, tosses it back to in front of the monkey. The monkeys kicks again and this time the goalie blocks the shot by catching the ball.
  • The monkey is sad.

Assignment