MIC 212

1
MIC 212

• Introduction to Games Programming in Visual Basic
  6
• Semester 2
• 2004

2
Lecture 2

• Games programming
• Visual Basic Programming

3
Games Programming

• Example game program outline
• Display title screen
• Load sprites and sound
• Display a static or rendered background
• Check for input and update the players position
• Process enemy positions using AI
• Move each sprite to the new location
• Check for collisions between the sprites
• Increment the animation frame for each sprite
• Loop back to step 4 until game over
• Delete all game objects and free memory
• End game

4
Key games programming steps

• Initialisation of all media
• Graphics, sounds, animation, text
• Main event loop
• Responding to user input
• Moving the game on
• Moving sprites (objects that clean up after
  themselves)
• Animating sprites moving through frame cycle
• Game logic checking for collisions, computing
  next action for all objects, calculating scores,
  levels, configuration phases, game over?
• Game end
• Highest score, bonus etc.

5
Games programming in Visual Basic

• Initialisation of objects
• properties
• Main event loop programming
• Responding to user input
• Setting properties
• call back methods, e.g., Timer1_Timer()
• Game logic
• Call back methods, subs
• File and database management

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Step when creating a VB 6 program

• Create the Interface using forms editor
• Set initial values for control properties
• Write code for event handlers (call backs)

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Changing properties

• Controls (and other objects) have properties
  which have (constant) values
• To change during design
• Type the required value in the properties window
• To change during the program (run-time)
• Write code to set the value for a property

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Changing colours palette
9
Writing Event Handlers

• A.k.a procedures, subs, methods
• Add/select a control.
• Double click on the control to open the Code
  window.
• Click on the Procedure box (upper right drop
  down) to find the event
• Write the code for that event.

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Example

• Event handler for click event for Button
• VB puts standard code in automatically
• You complete the missing statements
• Private Sub cmdButton_Click( )
• txtBox.ForeColor vbRed
• txtBox.Font.Size 24
• txtBox.Text Hello
• End Sub

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Coding standards

• Inline comments
• set the background colour to red when the form
  loads
• How does this work in a program?
• --------------------------------------------------
  -
• Option explicit
• Private sub Form_load()
• set the background colour to red when the form
  loads
• Form1.backcolorvbred
• End sub

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Components of VB 6 Statements

• Variables and Constants
• Keywords (reserved words)
• Operators and functions (including properties)
• txtBox.ForeColor vbRed

Property (selection function)
Constant
Assignment Operator
Variable
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Variables

• A storage location in main memory whose value can
  change during program execution.
• These storage locations can be referred to by
  their names (restrictions first letter, , .
  etc.)
• Every variable has a Name, a Value, and a Type
  (and a Scope covered next week)
• Example types Numeric and String
• Dim Amount As Integer
• Option Explicit forces declaration of variables -
  (General) (Declarations)
• Numeric types byte, boolean, integer, long,
  single, double, currency, decimal, date

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Keywords

• Words that have predefined meaning to Visual
  Basic.
• Can not be used as variable names.
• Examples Print
• Cls
• If
• While

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Numeric Variables

• Used to store numbers.
• The value is assigned either by the programmer or
  by calculation
• ApplesSold 10 ' The value 10 is assigned to the
  variable.
• ApplesSold ApplesSold 1 ' The variable is
  incremented.

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Constant

• Similar to a variable, but can NOT change during
  the execution of a program
• Can be declared (named, preferred)
• Const Modulus As Single 4.17825 ' Value cant
  change
• Or used directly (literal)
• tax 0.02 (income - 500 dependence)
• Types of Constants
• numeric constants
• string constants
• Many pre-defined, see Visual Basic Constants in
  Index of Help

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String Constants

• A sequence of alphanumeric data
• Contents depend on character set
• Usually ASCII with Roman alphabet and numerals,
  plus accents and a few symbols.

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Arithmetic Operations Hierarchy of Operations

• Operator operation Basic
  expression
• Exponentiation A
  B
• Multiplication A
  B
• / Division
  A / B
• Addition
  A B
• - Subtraction
  A B
• Hierarchy what gets done when if there are no
  brackets ab cd e
• and also work for strings!

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Built in methods

• Print is a method used to display data on the
  screen or printer.
• Can be used to print value of variables.
• Can be used to print value of arithmetic
  expressions.

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Example of Print Statements

• Private Sub cmdCompute_Click()
• picResults.Print 3 - 2
• picResults.Print 3 2
• picResults.Print 3 / 2
• picResults.Print 3 2
• picResults.Print 2 (3 4)
• End Sub

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Example of Print Statement

• picOutput.Print speed
• picOutput.Print taxRate
• picOutput.Print Class average is total / 3

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Example

• Dim x, y as integer
• x 15
• y 5
• picOutput.Print (x y) / 2, x / y

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Complex statements

• Conditionals
• If then else end if
• Select Case x
• Case 5 Console.WriteLine("x 5")
• Case 10 Console.WriteLine("x 10")
• Case 20 Console.WriteLine("x 20")
• Case 30 Console.WriteLine("x 30")
• End Select
• Loops

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Your first game a simple timed single player
activity-based game

• Aim to follow instructions to reveal 5 words,
  place them in a sentence and type in the answer
  to a simple question
• Player selects an answer and types in the textbox
• Message is displayed in response to
  correct/incorrect answer
• Player can retry

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Design

• Objects timer, labels (5 used to display text
  strings), textbox, 2 command buttons
• Events
• Timer starts as soon as game is started so player
  is timed on ability to assimilate instructions as
  well as complete the task
• Player clicks on the 5 squares to reveal the
  words
• Player clicks on button to submit answer