Brewing Your Brewing Your Own Game Own Game

EngineEngineThe Pros & Cons of Using Open Source Software to The Pros & Cons of Using Open Source Software to

Rapidly Develop Cross-platform Indie Games and ToolsRapidly Develop Cross-platform Indie Games and ToolsYe Feng

What’s In The Talk

No rocket science

From practical experience

Arguable

Who We Are

Project OneTap

One One ButtonButton

2D Action2D Action

Simple Simple PuzzlePuzzle

CasualCasual

CustomizabCustomizable Levelsle Levels

Challenge:Level Design

Wise Man Builds His House On The

Rock

Option 1: Cheap Commercial Engine

Option 2: Open Source Engine

Cheap Commercial Engine

Pros

IDE

Cross platform(when officially supported)

Moderate license fee

Cons

Offline IDE

Portability(when not officially supported)

No source code

Pure script driven

Open Source Engine

Pros

Source code

Cross platform

Free

Cons

No IDE

Pure native code driven

Open Source License

Choice

Option 1: Cheap Commercial Engine

Option 2: Open Source Engine

Option 3: Open Source Engine + Game Support Layer

Allegro

http://alleg.sourceforge.net/

✔

Demo

What’s In ItGame Object System

Script Integration

Physics Integration

Content pipeline tools

Others

Simple Scene Management

Action System

Script Key-Value Dictionary

etc...

Game Object System

Inheritance & Gameplay

Development

Gameplay dev nature: iteration

Iteration causes changes

Inheritance: not change-friendly

Good

Bad

Design Pattern

Favor object composition over class inheritance

Game Object & Game Component

Composition instead of inheritance

A object of gameplay logic

Is composed by multiple functional components

Game Game ObjectObject

Component Component #1#1

Component #2Component #2

Component #3Component #3

Game Object & Game Component

Add/remove component in runtime

Key to build an IDE

Composition To The Rescue

Basic ComponentsPositioning info: Transform

2D rendering: Sprite

Bitmap info: Bitmap Source

Input processing: Event Receiver

Rigid body entity: Body

Collider entity: Fixture

Particle effect: Particle Emitter

etc...

User Components

Arbitrary stuff that gameplay needs

Rotation forever

A goal in level

The behavior of characters

A spike need to be avoided

Line drawer needed by editor

etc...

Demo

Script Integration

Dilemma of Native

Compilation time

Runtime modification

Advanced language feature

“Glue” code

2-tiers System To The Rescue

Core: native code

Editor and gameplay: script

Lua

Related Works

Communication between native and script

Export tools/libraries

Script API

Communication - Native & Script

Simple interfaces/engine API

tolua

http://www.tecgraf.puc-rio.br/~celes/tolua/

Simple, no compilation cost

Complex interfaces

Lua C API

Related Works cont.

Serialization

Load/save, editor

Support for advanced features

Reference

Function object, closure

etc...

Serialization

Pluto

https://github.com/hoelzro/pluto

Write serialization code for every component

1000 lines of Lua code

Prefabricated Object

Take snapshot of object

Parameters

References

Hierarchy

Assisted object design

Level editor ➔ object editor

Patching

Patching binary ➔ patching data

Demo

Content Pipeline Tools

DCC Tools

Flash?

StaticStatic

AnimationAnimation

Pipeline

FlashFlash

PhotoshoPhotoshopp

ExporExportt ManuallManuall

y y Created Created

AtlasAtlas

IDEIDE

GameGame

☹

Solution

swfdec

Open source Flash player

LGPL

swfdec-dumper

Surface ➔ disk

https://github.com/fengye/swfdec-dumper

Pipeline 2.0

StaticStatic

AnimationAnimation

FlashFlash

PhotoshoPhotoshopp

IDEIDE

GameGame

swfdec swfdec dumpedumpe

rr ManuallManually y

Created Created AtlasAtlas

☹☺

Atlas Tool

Stitch bitmap into Atlas

Automation

Transparent process

Texture Atlas Gen

nVidia Texture Atlas Tools

File format support☺

Mipmap☺

Free☺

Only for sprite sheets☹

Pack algorithm

Pipeline 3.0

StaticStatic

AnimationAnimation

FlashFlash

PhotoshoPhotoshopp

IDEIDE

GameGame

swfdec swfdec dumpedumpe

rr Texture Texture Atlas Atlas GenGen

☺☺

Questions?