Java Gaming

1
Java Gaming

• An overview

2
Content

• Demos
• Some game types
• Java as Game language
• Game building issues
• APIs for 2D game development
• APIs for 3D game development
• APIs for Mobile game development
• Example of game engines
• Installation

3
Some other reading.
4
Some game types

• Arcade games
• 2D Games
• 2D Side scroller
• Isometric tile games
• 3D games
• FPS First Person Shooter
• 3D Mazes
• Network games

5
Why not Java?

• To slow?
• Java isnt slow anymore!
• Most of a graphic Game is handled by HW
• Memory problems?
• Avoiding/ensuring GC is about programming style
• To high level?
• C/C was that too!!
• High level OO helps design of complex games
• Many new APIs for game support
• Jni

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Why not Java?

• Installation nightmare
• Code bloat of JVM well most games today are
  100MB
• Slow startup Yes, but is a small part of game
  time!
• Installation Java Webstart Install4j
• Support
• Sun is more active to add APIs for games
• Game consoles doesnt support Java! (80 market)
• But, modern mobile phones support Java!

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Game Framework

• Game loop
• Sprites, Animated sprites e.g explosions
• Collision detection
• Pausing, exit
• Image repository (loading and sharing)
• Model repository
• Sound player repository (Midi, mp3 clips)
• Object manager control the GC
• Input handling mouse, keyboard, game pad etc
• Boards e.g. High score list

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Its all about time

• Update of screen
• No flicker
• No stops hack in viewing
• Same update speed on all HW
• Update of game state
• More important than update of screen

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Time Control

• Keeping constant time
• FPS Frames Per Second
• UPS Updates Per Second
• Normally 70-80 FPS
• Upper bound is the monitor refresh rate (70-90 Hz)

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Measuring Time

• Resolution of time OS dependent
• System.currentTimeMillis() resolution 1-60 ms
• System.nanoTime() Java 5 resolution 1-6 ms
• Java.util.concurrent.TimeUnit Java 5 ns
  resolution
• J3DTimer Java3D resolution 200-900 ns
• Other timers
• javax.swing.Timer and java.utility.Timer uses
  System.currentTimeMillis() and is hard to
  control
• Timer in Java Media Framework JMF
• Game engines

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Sleeping Better

• Sleeping
• The Thread.sleep() accuracy is OS dependent
  (10-20 error for a 1 ms sleep time)
• Oversleep must be handled

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A game loop
Finished?
Yes
End loop
No
Update game state
Render game state
Time calculations
Sleep?
No
Yes
Sleep calc over sleep
late?
No
Yes
Update game state
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while(running) // Game loop
gameUpdate() gameRender() //
render the game to a buffer paintScreen()
// draw the buffer on-screen afterTime
J3DTimer.getValue() timeDiff afterTime -
beforeTime sleepTime (period - timeDiff) -
overSleepTime if (sleepTime 0) //
some time left in this cycle try
Thread.sleep(sleepTime/1000000L) // nano
- ms catch(InterruptedException ex)
overSleepTime (J3DTimer.getValue() -
afterTime) - sleepTime else
// sleepTime the period excess - sleepTime // store
excess time value overSleepTime 0L
if (noDelays NO_DELAYS_PER_YIELD)
Thread.yield() // give another thread a
chance to run noDelays 0
beforeTime J3DTimer.getValue() / If
frame animation is taking too long, update the
game state without rendering it, to get
the updates/sec nearer to the required FPS. /
int skips 0 while((excess period)
(skips period skips gameUpdate() //
update state but don't render
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A little about Collision Detection

• Boundary check
• Complex figures are approximated
• Bit overlap
• One step-ahead
• In 3D its about vector mathematics
• Sphere plane collision
• Boundary box
• Ray tracing
• And time
• Dont forget large steps
• Finally what to do
• Explode, Bounce, Stop, Penetrate..

15
2D and Isometric Game issues

• Choice of view
• FSEM or Windows
• 2D v.s. Isometric
• Screen size and resolution
• Moving backgrounds
• Planning time for loading and GC
• Graphic and sound
• Background
• Event effects sound synchronized
• Choice of input

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Some 2D and Isometric algorithms

• Collision detection
• Map creation
• Path finding
• A - find the lowest cost way from A to B
• D - dynamic A
• Flocking

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A path finding
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Some 3D Game issues

• Scene graph the world
• Floor, boundaries, Sky
• Creating and loading models
• Combining 2D and 3D
• Sprites, menu's etc
• Viewer position and movement
• First person camera
• Hovering following camera
• Gravity ground follower, flyer
• Picking
• Lightning
• Collision detection

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Some 3D Game effects algorithms

• Particle systems
• Flocking
• Growing trees
• Level of detail

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Desktop APIs for game development

• Basics
• JDK
• Graphics
• FSEM, Java 2D, Java 3D, (JOGL, LWJGL, GL4Java)
• Sound
• JOAL / Sound 3D, JMF
• Control
• JInput
• Distribution
• Java WebStart, Install4j
• Other
• ODEJava

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Some Free Game Engines

• Free 2D game engines
• Meat Fighter - http//meatfighter.com
• GAGE - http//java.dnsalias.com
• GTGE - http//goldenstudios.or.id/products/GTGE
• Free 3D game engines
• Jake2 (Quake2) - http//bytonic.de/html/jake2.html
  
• JGE - https//jge.dev.java.net
• JME - http//www.jmonkeyengine.com/

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JME Game picture
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Building 3D worlds

• Design tools
• 3D Studio Max
• Maya - Autodesk
• Terragen
• Monkey World 3D
• Many more
• Some file formats
• DXF - Autodesk
• VRML
• M3G Mobile (JSR184)
• MD2 QuakeII

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Mobile Game issues

• Small memory
• Low processor speed
• Lack of floating point calc HW support
• Small screens
• Inconsistent capability between phones
• Configuration of screen, MIDP version, input etc
• Distribution of many configuration versions
• More

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Mobile APIs for game development

• Basics
• MIDP1.0, MIDP2.0 - Java Game (JSR 134)
• Graphics
• Java Game (Sprites), Mobile Java 3D (JSR183),
  Java Bindings For OpenGL ES (JSR 239), Mascot
  Capsule Micro3D Engine
• Sound
• Java Game, Mobile Media API (JSR 135)
• Control
• Java Game
• Networking
• Threads
• Distribution

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Network games topology
Ring
Star
host1
host1
Server
host5
host2
host5
host2
host4
host3
host4
host3
host1
host5
host2
All-to-all Peer-to-Peer
host4
host3
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Network games - issues

• Protocol - UDP, TCP, http, IP multicasting
• Game type
• Bandwidth, firewalls, robustness
• Fat client vs. fat server logic
• Security
• Transport
• Anonymous users
• More

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Java networking APIs

• Plain sockets UDP/ TCP,
• Java Secure Sockets Extension - SSL TLS
• IP multicasting P2P JXTA www.jxta.org
• URL class
• J2EE Servlets
• Applets (Multicast ?)
• RMI
• Service Architecture
• Jini
• WebServices e.g Axis
• Sun Project Darkstar MMORGP (Massive Multiplayer
  Online Roleplaying Game Platform)

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Packaging and Distribution

• Java WebStart
• Install4J