Component-based Entity System

in Mobile Game Development

Cody Nguyen (cody.haind@gmail.com)

Game Architecture

Bigger project needs better architecture

What is a good architecture?

A good architecture…

• Is easy to understand & maintain

• Welcomes changes

• Maximizes code reuse, minimizes duplication

Why does VTT need a good architecture?

Big game (dev-wise)

• Online tower defense, card collection on mobile

Big game (dev-wise)

• > 500 characters w/ different upgrade strategies

Big game (dev-wise)

• > 500 characters w/ different upgrade strategies

Big game (dev-wise)

• > 500 characters w/ different upgrade strategies

Big game (dev-wise)

• > 500 characters w/ different upgrade strategies

Big game (dev-wise)

• Complex items system: equip, enhance, forge

Big game (dev-wise)

• Complex items system: equip, enhance, forge

Big game (dev-wise)

• Complex items system: equip, enhance, forge

Big game (dev-wise)

• 8 game modes for the 500 characters to perform

Big game (dev-wise)

• 8 game modes for the 500 characters to perform

Big game (dev-wise)

• 8 game modes for the 500 characters to perform

Big game (dev-wise)

• 8 game modes for the 500 characters to perform

Big game (dev-wise)

• 8 game modes for the 500 characters to perform

Big game (dev-wise)

• 8 game modes for the 500 characters to perform

Game data & config need to be human-friendly and easy to change

• Game designers & operators are lazy human beings

Anh Cody ơi giảm base dam,

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em

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Short on time, while requirements change fast

• Reuse as much as possible

• Adapt to change

What is the most suitable architecture for VTT?

OOP?

• Easy to understand

• Suitable for small project

Game objects usually share common (set of) functionalities

Bird Collision, Graphics, Animation, TouchHandling

Pipe Collision, Graphics, Movement

Ground Collision, Graphics, Movement

Inheritance

Collidable

(Collision)

Pipe Checkpoint

Renderable

Animatable

(Animation)

Bird

Movable

(Movement)

Pipe Ground

Inheritance

Collidable

(Collision)

Pipe Checkpoint

Renderable

Animatable

(Animation)

Bird

Movable

(Movement)

Pipe Ground

Mixins or Multiple-inheritance. No!!!

Bird Pipe Ground

Collidable

(Collision) Renderable

Animatable

(Animation)

Movable

(Movement)

Pipe Checkpoint

Base Game Object

It’s hard to create a good OO architecture for bigger & more

complicated games

• Impossible to build a good OOP class hierachy

• Where to put logic code that process objects of 2+

different classes?

• Easy to make mistake when working in team

Component-based entity system

Component-based Entity System

• A hot topics in recent years

• Unity3D is an example

Component-based Entity System

• Multitude of ways to

represent & implement

Component-based Entity System

3 components:

• Entity

• Component

• System

Entities – Components

Graphics Anim Move Along Path

Attack Skill Collection Bonus

Officer (defend) x x x x x

Officer (run) x x x

Soldier (defend) x x x

Soldier (run) x x x

Animal x x x

• Decompose game entities by capabilities into reusable components

– Components contains only data

– Each entity has an unique ID and a list of components

• Create entities by picking the desired components

Systems

• Divide game aspects into systems

• Systems process only entities they care about in each game loop

Move Along Path Sys

Animation Sys

Collection Bonus Sys Attack Sys Skill Sys

Officer (defend)

Officer (run) Soldier

(defend) Soldier (run) Animal

Entities – Components - Systems

Artemis Entity System

• An open-source Entity System Framework originally

written in Java

• Ported to many languages

Benefits

Goes hand-in-hand with Data-Driven Methodology

• Components are just data, separated from game logic. Entities are just

bag of components

– Can be stored & retrieved from anywhere

– Human can make changes easily

MongoDB as database

• Flexible data structure, welcomes changes

• Easy synchronization between client / backend

Easy synchronization between client / backend

Easy synchronization between client / backend

Promote multi-threading

• Systems are independent from one another

-> can be run in separate threads

Conclusions

Online Game + Entity System = WIN

References

• A Data-Driven Game Object System

http://scottbilas.com/files/2002/gdc_san_jose/game_objects_slides.ppt

• Entity Systems are the future of MMOG development

http://t-machine.org/index.php/2007/11/11/entity-systems-are-the-

future-of-mmog-development-part-2/

• Evolve Your Hierarchy

http://cowboyprogramming.com/2007/01/05/evolve-your-heirachy/

• http://gamedev.stackexchange.com/a/31491

THANK YOU!