Unit 5Game Animation

Agenda

• 20 minBug Hunting

• 30 minDanger and Target Movement

• 15 minProjectile Movement (Optional)

• 5 minClosing

Product Outcomes:

• Students will add danger movement to their games

• Students will add target movement to their games

• Students will add projectile movement to their games

Standards and Evidence Statements:

Standards with prefix BS are specific to Bootstrap; others are from the Common Core. Mouse over each standard to see its corresponding evidence statements. Our Standards Document shows which units cover each standard.

• F-IF.1-3: The student uses function notation to describe, evaluate, and interpret functions in terms of domain and range

  • evaluation of functions using function notation for inputs in their domains

• F-LE.5: The student interprets expressions for functions in terms of the situations they model

  • interpretation of the parameters in a linear or exponential function in terms of a context

• BS-DR.2: The student can derive test cases for a given contract and purpose statement

  • given a Contract and a Purpose Statement, write multiple examples or test cases

  • given multiple examples, identify patterns in order to label and name the variables

• BS-DR.3: Given mutiple test cases, the student can define a function

  • given examples and labeled variable(s), define the function

• BS-IDE: The student is familiar with using a REPL, entering expressions properly, and interpreting error messages

  • look to error messages as a way of diagnosing syntax errors

• BS-PL.1: The student is familiar with declaring values and applying built-in functions using the programming language

  • interpreting a function application and identifying its arguments

• BS-PL.2: The student is comfortable using and writing Contracts for built-in functions

  • representing a function’s input and output using a contract

  • identifying correct and incorrect use of a function, based on its contract

• BS-PL.3: The student is able to use the syntax of the programming language to define values and functions

  • defining and using functions

Length: 70 minutes

Glossary:

• contract: a statement of the name, domain, and range of a function

• example: shows the use of a function on specific inputs and the computation the function should perform on those inputs

• purpose statement: a brief description of what a function does

• variable: something that changes

Materials:

• Pens/pencils for the students, fresh whiteboard markers for teachers

• Class poster (List of rules, language table, course calendar)

• Language Table (see below)

• Bug Hunting [Bugs.rkt from source-files.zip | WeScheme] file preloaded on students’ machines, as the front-most window.

• Student workbook

• All student computers should have their game templates pre-loaded, with their image files linked in

Preparation:

• OPTIONAL: Hand out Warmup activity sheet.

Types	Functions
Number	+ - * / sqr sqrt expt
String	string-append string-length
Image	rectangle circle triangle ellipse star text scale rotate put-image

Bug Hunting

Overview

Learning Objectives

• Gain more experience understanding and correcting programming errors

Evidence Statements

• Students will be able to read error messages for basic syntax errors

• Students will be able to edit programs to eliminate basic syntax errors

Product Outcomes

Materials

• Pens/pencils for the students, fresh whiteboard markers for teachers

• Class poster (List of rules, language table, course calendar)

• Language Table (see below)

• Bug Hunting [Bugs.rkt from source-files.zip | WeScheme] file preloaded on students’ machines, as the front-most window.

Preparation

Bug Hunting (Time 20 minutes)

• Debugging (finding and correcting problems in code) is an important part of programming, so it’s a good idea to practice finding bugs in code.

  Open the Bug Hunting program in a new window, and see if you can find the bug in each expression. Click "Run" and read the error message carefully! After you fix each one, clicking Run will show you the error message for the next bug.

  Make sure students understand that the goal is not to FIX the bugs, but rather just to find them.

Danger and Target Movement

Overview

Students model animation in the coordinate plane, and write a simple linear function that animates their Danger.

Learning Objectives

• Students learn to move game elements through functions that compute attributes in one frame from attributes in the previous frame

Evidence Statements

• Students will be able to write functions that take in one dimension of a game element’s coordinate and produce the next coordinate value in that dimension

• Students will learn how to control speed of movement through functions

Product Outcomes

• Students will add danger movement to their games

• Students will add target movement to their games

Materials

• Pens/pencils for the students, fresh whiteboard markers for teachers

• Student workbook

• All student computers should have their game templates pre-loaded, with their image files linked in

• Class poster (List of rules, language table, course calendar)

• Language Table (see below)

Preparation

• OPTIONAL: Hand out Warmup activity sheet.

Danger and Target Movement (Time 30 minutes)

• The dimensions of your videogame are 640x480, and each character is placed on the screen at a set of (x,y) coordinates. Your Target (T), Player (P) and Danger (D) each move along the x- or y-axis, having their x- or y-coordinate changed according to an animation function. These animation functions will start off simple: they take in the current x- or y-coordinate, and produce the next x- or y-coordinate. Later on you’ll be able to adapt them to create more sophisticated motion, using both the x- and y-coordinates.

• Turn to Page 16 in your workbook for update-danger.

  • Read the word problem carefully, and pay attention to what the function takes in.

  • Fill out the Contract and Purpose Statement for the function, using what you circled to help you choose the Domain.

  • Write two Examples for the function.

  • Circle and label what varies between those examples, and label it with a variable name.

  • Define the function.

  If students are working on their own, check their work to make sure every last step is being executed correctly. If the class is working through it together, be sure to ask students to justify each step in terms of a prior step. Tip: tell students that they must get your permission before typing in their code, then use that expectation to check each student’s paper carefully.

• Putting all of these together, update-danger is defined by:   ; subtract 50 from the danger's x-coordinate (EXAMPLE (update-danger 171) (- 171 50)) (EXAMPLE (update-danger -90) (- -90 50)) (define (update-danger x) (- x 50)) (Note: you may have slightly different Examples or variable names.)

  Open your saved Game file and scroll until you find the definition for update-danger. Is the contract correct? Make sure it matches what you have in your workbook, add both of your examples, and fix the definition. When you click "Run" you should see your danger fly across the screen!

• Now it’s time to animate the Target, which moves in the opposite direction.

  Turn to Page 17 in your workbook for update-target.

  • Read the word problem carefully, and pay attention to what the function takes in.

  • Fill out the Contract and Purpose Statement for the function, using what you circled to help you choose the Domain.

  • Write two Examples for the function.

  • Circle and label what varies between those examples, and label it with a variable name.

  • Define the function.

  For students who finish these quickly, have them experiment with making the Target and Danger move faster or slower, or change direction altogether. Be sure that they are typing in Examples, and updating those examples to keep up with any changes to their definition.

Projectile Movement (Optional)

Overview

OPTIONAL: students discover that the "mystery" definitions in the game are actually used to add projetiles, and adapt these definitions to add a custom projectile and projectile animation to their game.

Learning Objectives

• Students learn to move game elements through functions that compute attributes in one frame from attributes in the previous frame

Evidence Statements

• Students will be able to write functions that take in one dimension of a game element’s coordinate and produce the next coordinate value in that dimension

Product Outcomes

• Students will add projectile movement to their games

Materials

Preparation

Projectile Movement (Optional) (Time 15 minutes)

• This game template also has a mystery object, which is defined at the very bottom of the screen. The "mystery" is actually a projectile, which will be set to the Player’s position whenever the spacebar is pressed. As you can see, mystery is defined to be a small gray star, but you can change that to be any image you like. If you have a game in which the player is a monkey, you could change the definition of mystery to be a bitmap of a banana, so that the monkey will throw bananas every time you hit the spacebar. A game that takes place in space could have an alien throwing crystals, or a sports game might involve an athlete thowing a ball.

  • Change the definition for mystery, so that your projectile looks the way you want it to. Don’t forget to use scale and rotate if you need to change the image slightly.

  • Use the Design Recipe to write update-mystery, so that the projectile moves to the left or right. Hint: this will be very similar to your solutions for update-danger and update-target!

  Be careful when introducing Projectiles into the game! Many students will actually be less creative when using them, as it will automatically push their mindset towards the standards "shoot the bad guy" format. Many teachers choose to skip this section entirely, or else add it after the games are complete.

Closing

Overview

Learning Objectives

Evidence Statements

Product Outcomes

Materials

Preparation

Closing (Time 5 minutes)

• Congratulations - you’ve got the beginnings of a working game! However, several things remain unfinished:

  • The Player doesn’t move

  • When the Target and Danger move offscreen, they never come back

  • Nothing happens when the Player collides with the Danger or Target

  The next few lessons will extend what you know about functions, so that you can define functions to implement each of these features.

  • Have students volunteer what they learned in this lesson

  • Reward behaviors that you value: teamwork, note-taking, engagement, etc

  • Pass out exit slips, dismiss, clean up.

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