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CS329e – Elements of Visual Programming. Implementing Programs Mike Scott (Slides 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
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CS329e – Elements of Visual Programming Implementing Programs Mike Scott (Slides 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
Last Time • Given a problem we want to solve it by creating an animation • Create storyboard / script • snowman example • bike race example Implementing Programs
Initial Scenes Implementing Programs
Initial Scenes Implementing Programs
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
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
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
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
Action Blocks in Alice Sequential Action Block Simultaneous Action Block Implementing Programs
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
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
Method Editor Window Implementing Programs
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
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
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
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
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
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
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
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
Corrected Do Together Implementing Programs
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
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
Comments Notes: 1) Comments appear in green 2) Alice ignores comments. 3) Comments make the program easier to read. Implementing Programs
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
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
Alter the Vehicle Property • Select sax from object tree • Select properties tab • Change vehicle from world to snowman Implementing Programs