Joe Chung
Monmouth U. Homepage

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====== Scrolling, Sound, AI ======

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===== Scrolling Games =====

    * Example: Super Mario Brothers
      * Game that travels left or right well beyond the length of the game panel
    * Graphics requirement: tile maps (a.k.a., "bricklaying")
    * Backgrounds are often composed of several tile map layers
    * Scrolling Demo:
      * The following example illustrates a wrap-around "ribbon" background.
      * [[http://rockhopper.monmouth.edu/~jchung/cs498gd/fa09/labs/scroll/ScrollDemo.java|ScrollDemo.java]] (main program)
      * [[http://rockhopper.monmouth.edu/~jchung/cs498gd/fa09/labs/scroll/ScrollPanel.java|ScrollPanel.java]]
      * [[http://rockhopper.monmouth.edu/~jchung/cs498gd/fa09/labs/scroll/Ribbon.java|Ribbon.java]]
      * [[http://rockhopper.monmouth.edu/~jchung/cs498gd/fa09/labs/scroll/mario-1-1.gif|mario-1-1.gif]]

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===== Sound Basics =====

  * Two types of sound used in games
    * Sampled audio data - Series of digital values that represent the amplitude or intensity of sound pressure waves
      * Most often used for game //feedback// (i.e. audio effects)
      * Support for encoded/compressed audio (e.g. mp3) is also used in games.
    * Synthesized audio data
      * Example: MIDI (Musical Instrument Digital Interface) - A standard electronics communications protocol
        * used in a many video games (in almost all NES games)
      * Most often used for game //atmosphere// (i.e. background music)

==== Playing a Sound in Java ====

=== Java Sound API ===

    * Allows access to (and manipulation of) audio data and the underlying machine's audio hardware and software
    * The packages: ([[http://rockhopper.monmouth.edu/~jchung/cs498gd/fa09/labs/animation/animatedSprites/SoundPlayback.java|SoundPlayback.java]])
          * javax.sound.sampled.*
                * Handles digital audio data
                   * Supports WAV, AU, and AIFF formats, and can be extended to support more formats such as mp3
                * Going beyond simple sound playback:
                  * Port - I/O to microphone, speaker, etc.
                  * Mixer - Audio device with multiple I/O lines
                  * DataLine - Adds functionality to a line, including start, stop, and pause audio.
                  * GainControl - Used to manipulate an audio signal's volume
                  * PanControl - Used to control the balance between the left and right stereo channels

  * Example: Simple sound recording application with playback
    * [[http://rockhopper.monmouth.edu/~jchung/cs498gd/fa09/labs/sound/RecorderApp.java|RecorderApp.java]]
    * [[http://rockhopper.monmouth.edu/~jchung/cs498gd/fa09/labs/sound/icons/play.gif|play.gif]]
    * [[http://rockhopper.monmouth.edu/~jchung/cs498gd/fa09/labs/sound/icons/record.gif|record.gif]]
    * [[http://rockhopper.monmouth.edu/~jchung/cs498gd/fa09/labs/sound/icons/stopplay.gif|stopplay.gif]]
    * [[http://rockhopper.monmouth.edu/~jchung/cs498gd/fa09/labs/sound/icons/stoprec.gif|stoprec.gif]]

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===== Game AI =====

  * What is AI?
    * The study of computational systems that "exhibit intelligence"
    * Capabilities: problem solving, planning, and learning

  * "AI" in Games (note the double quotes)
    * Opponents (e.g., how can they outsmart you?)
    * Computer teammates
    * Support characters and autonomous characters (NPCs - non-player characters)
    * Commentators (sports games)
    * Camera control
    * Plot control (story branching)
    * Some goals of AI in games:
          * Provide challenging opponents...
            * ...but not too challenging or too predictable
          * Gather enough knowledge...
            * ...but aim for low CPU and memory usage
          * Provide an illusion of reality (e.g., human characteristics)

  * Experiences with game AI? Game-generated opponents that you thought were well done?

  * Effects of Bad AI
    * Reduced fun
    * Extreme behaviors (from lame to superhuman)
    * Unrealistic behaviors
    * Mindless hordes (of opponents)
    * Cheating

  * Sample Problems for a game AI
    * What to do when the enemy is heard or sensed?
    * What to do when AI-controlled character health level is low?
    * What to do if AI-controlled character doesn't see or hear anything? (idle time)
    * How to move from point A to the goal in a maze?
    * How to move a flock of objects (e.g., birds)?

  * Building a game AI agent
    * Given: the environment
    * Cycle (one iteration of the game loop):
          * Sense - Gather information about the environment
          * Think - Use some decision-making routine
          * Act - Execute something based on the decision
          * Repeat steps
    * Some constraints:
          * Memory: What to remember and for how long?
          * CPU usage

==== Finite State Machines (FSM) ====

    * Glossary:
      * FSM - A collection of states and transitions that outline a path of actions that may occur.
      * State - A state is a position in time.
        * For example, when you are at the bus stop, you are currently in a waiting state.
      * Event - An event is something that happens in time.
        * For example, the bus has arrived.
      * Action - A task performed given a certain event that occurred.
        * For example, you enter the bus.
      * Transition - A link between 2 states.
        * May be unidirectional or bidirectional.

    * Possibly the simplest type of game AI decision-making engine
    * Looks like the [[http://rockhopper.monmouth.edu/~jchung/cs498gd/fa11/lect/flauncyStateDiag2.png|state diagrams]] in game design documents
      * Also see http://www.generation5.org/content/2003/FSM_Tutorial.asp
    * Strengths:
          * Simple, quick
          * Can be compacted into a simple data structure such as an array

  * Finite State Machine Example: Quake II
    * 9 different states for AI-controlled enemies
          * Standing
          * Walking
          * Running
          * Dodging
          * Attaching
          * Melee
          * See the enemy
          * Idle
          * Searching

==== References ====

    * http://www.generation5.org/content/2000/app_game.asp
    * http://www.cs.northwestern.edu/~forbus/c95-gd/lectures/Game_AI_Introduction.pdf
    * http://www.bit-tech.net/gaming/2009/03/05/how-ai-in-games-works/1
    * http://www.generation5.org/content/2003/FSM_Tutorial.asp

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