CS329e – Elements of Visual Programming

1. CS329e – Elements of Visual Programming Implementing Programs Mike Scott (Slides 2-2)

2. What We Will Do Today • Cover how to implement a program after the storyboard is created • Work on examples in the lab: • Exercise 2.4 on page 48. Circling Fish • Exercise 2.5 on page 48. Tortoise Gets Cookie • Answer questions about assignment 1 Implementing Programs

3. Last Time • Given a problem we want to solve it by creating an animation • Create storyboard / script • snowman example • bike race example Implementing Programs

4. Initial Scenes Implementing Programs

5. Initial Scenes Implementing Programs

6. Techniques and Tools • Mouse used to • set up the initial scene • approximately position objects in the scene • resize and rotate objects • Camera Navigation is used to • set the camera point of view • Drop-down menu methods are used to • resize objects and rotate objects • more precisely position objects in the scene • Scene Editor's Quad View is used to • obtain specific alignments • position one object relative to another object Implementing Programs

7. Writing A Program • "Writing" a program (script) • a list of instructions to have the objects perform certain actions in the animation • Our planned story board (to do list) is Snowman turns to face snowwoman Snowman blinks and addresses snowwomen Snowwoman turns around • Now translate design steps into program instructions Implementing Programs

8. Translating the Design • Some steps in the storyboard can be written as a singleinstruction • The snowman turns to face the snowwoman • Other steps are composite actions that require more than one instruction Snowman blinks and addresses snowwomen • blinks -> Snowman raises and lowers his eyes • addresses -> Snowman says “ahem” Implementing Programs

9. Actions • Sequential • Some actions occur one after the other • first step (snowman turns to face snowwoman) • second step (snowman tries to get snowwoman’s attention) • Simultaneous • Other actions occur at the same time • Snowman says "Ahem" and while simultaneously blinking his eyes Implementing Programs

10. Action Blocks in Alice Sequential Action Block Simultaneous Action Block Implementing Programs

11. Writing the Program • In Simple Animations notice the only event • world.my first method • world is an object (contains all other objects) • my first method is a method. A behavior of a certain objects • methods consist of a series of instructions and commands (some of which may be other methods…) • big rocks into little rocks Implementing Programs

12. Adding Instructions to world.my first method • The method should be open in the method editor window of Alice. (bottom right) • if not select the world from the object tree, the method tab, and click the edit button next to my first method Implementing Programs

13. Method Editor Window Implementing Programs

14. Step 1 – Snowman turns • Select the object you want to perform the object • Select the method / action you want the object to perform • could use turn or turn to face • often many ways to accomplish the same task • Click and drag it to the method editor window Implementing Programs

15. Snowman Turns • Can adjust aspects of how the snowman turns to face the snowwoman • click the more option • right now duration and style are the only things you should alter Implementing Programs

16. Step 2 – Combined Action • We want the snowman to say “ahem” and blink at the same time • actions are normally sequential • to do actions together, at the same time, use a “Do together” block • Click and drag “Dotogether” block intothe method Implementing Programs

17. Step 2 – Combined Actions • Now drag the things we want to happen together into the “Do together” block • Snowman say ahem • Snowman blink – raise and lower eyes Implementing Programs

18. Affecting subparts • The snowman does not have “blink eyes” method • Can accomplish a blink by affecting subparts • Select snowman object from object tree and expand subparts • expand the head • now we can give commands to individual parts, in this case the eyes • have eyes move up and down • specify directionand distanceof move Implementing Programs

19. Step 2 – First Attempt • world.my first method looks like this • TEST the method • play the movie. Does it do what we want? Implementing Programs

20. Logic Error • The program works, but does not do what we intended. • This is an example of a logic error • very easy in Alice to see logic errors • the movie does not do what we wanted • What’s the problem? Implementing Programs

21. Do together and Do in order • All commands in the Do together block are executed simultaneously • So what is the result if you move an eye up .1 meters and down .1 meters at the same time? • Apparently nothing • So while we want the eyes to move together and to say “ahem” we want the eyes to first move up and then down • Use a Do in order block inside the Do together block Implementing Programs

22. Corrected Do Together Implementing Programs

23. Testing • An important step in creating a program is to run it – to be sure it does what you expect it to do. • We recommend that you use an incremental development process: • write a few lines of code and then run it • write a few more lines and run it • write a few more lines and run it… • This process allows you to find any problems and fix them as you go along. • As you go you may alter your design / storyboard • design a little, code a little, test a little… Implementing Programs

24. Comments • While Alice instructions are easy to understand, it is often desirable to be able to explain (in English) what is going on in a program • We use comments to explain to the human reader what a particular section of code does Implementing Programs

25. Comments Notes: 1) Comments appear in green 2) Alice ignores comments. 3) Comments make the program easier to read. Implementing Programs

26. Extra – Moving Together • To move things together can sometimes be a pain • Tell two objects to move “forward” • directions are relative to the objects • may get motion in different directions • can use the “orient to” method to synch frames of reference Implementing Programs

27. Vehicles • Each object has a vehicle property • Initially the world is the vehicle for objects • can change this by altering the vehicle property for an object • Give the snowman an instrument • Change “ahem” to “toot” • What happens when movie played? Implementing Programs

28. Alter the Vehicle Property • Select sax from object tree • Select properties tab • Change vehicle from world to snowman Implementing Programs