An Innovative wireless PDA Game

Leung Pui Yin, Carol

Lo Man Kit, Marcus

Outline IntroductionTechnologies in our projectPocket PC programming techniquesSnapshot of our projectFuture workConclusionQ&A

IntroductionCurrent Pocket PC game

Two players only Wired connection

In our project, we will implement a complete wireless multiplayer Pocket PC game on Bluetooth

Technologies in our projectBluetoothGame API

Technologies in our projectBluetooth

Two Bluetooth equipped devices can establish a connection together within 10 meters range of each other.

It utilizes a radio-based link, so does not require a line-of-sight connection in order to communicate.

Technologies in our projectGame API

Handling graphics much more efficiently Useful to write blazing-fast games

Difference between GDI and GAPI

User Code

Display Hardware

Display Driver

Video Memory

Windows GDI

Device ContextDevice Context

Display Hardware

Display Driver

Video Memory

Windows CE GAPI

Device ContextUser Code

Advantages of GAPIBy bypassing Window CE GDI entirely,

Game API allow programmers to directly access to Pocket PC video memory.

It is useful in writing high-performance, real-time games.

It is useful for video playback and other graphics applications.

Limitations of GAPINo support for “BitBlt” or “TransparentI

mage”Need to write a custom BitBlt routine by

the programmer

Pocket PC programming techniquesPocket PC limitations

Computational Power Memory Screen Size

Due to these limitations, there are some problems that are not encountered in desktop PC programming.

Pocket PC Memory ManagementShutting down applications without

notifying user when memory is lowHappens when an application needs

more memory, e.g. instantiate more objects

Pocket PC Memory Management

Threshold Value Description

Hibernation 200 KB WM_HIBERNATE message sent to longest inactive application

Low-memory

128 KB WM_CLOSE message sent to longest inactive application

Critical-memory

24 KB No new applications can be opened.

Pocket PC Memory Management Implement a handler for the

WM_HIBERNATE message Attempt to release as many resources as

possible Avoid being closed unnoticeably

Game APIConventionally, the origin of a window is

at the upper-left corner.Also, the pixel bits in a bitmap are

organized in horizontal rows.However, the video memory retrieved

from GAPI may NOT be organized as stated above, depending on the model.

Game APICASIO Pocket PC series

NormalHP iPAQ series

Origin at lower-left corner Organized in vertical column

Game APISolution 1 - use GXDisplayProperties

*(VidMem +x * GXDisplayProperties.cbxPitch +y * GXDisplayProperties.cbyPitch)

Accessing a pixel needs TWO multiplications, which are quite slow in Pocket PC, especially when bitblting.

Game APISolution 2 - use specific code for

different model Much faster, comparing

*(vidmem + x * cbxPitch + y * cbyPitch) *(vidmem++)

in a for loop Troublesome to develop Many publicly available packages use this

method

ThreadSprites movement and graphics update

are performed one by one in game loop.Problems

The job of sprites movement may be lengthy.

The job of sprites movement would be done in a controlled way.

Frame rate may drop.

ThreadAccording to 1/10-second rule

mentioned by Charles Petzold, the job of sprites movement should be handled separately by another thread.

In our project, the job of each sprite movement and graphics update are handled by separate threads.

Thread PoolThread creation and thread termination

are very time consuming.Both thread creation and termination

occur frequently in a multi-player game using multi-threading.

We need to speed up these processes.

Thread Pool - Basic IdeaCreate enough threads at initial phase

to avoid dynamic allocation of threads in the middle of the game.

Not to terminate unused threads – reuse them when appropriate.

Object PoolSimilar to thread pool, the aim of object

pool is to reduce the overhead of object creation and termination.

The major difference is that object pool has to manage different kinds of objects.

Snapshot of our project

Snapshot of our project

Snapshot of our project

Snapshot of our project

Future workWireless Multi-player gameSynchronization problem on Bluetooth

and Pocket PC

ConclusionDeveloping games on Pocket PC has

its commercial values. It is a challenging task, involving many

latest technologies. It needs some attentions not commonly

noticed in desktop PC programming.

Q & A