Damián Isla, Moonshot Games

HEY INDIES,

IT’S A GREAT

TIME TO BUILD AN ENGIN

E

Unan

noun

ced

Disclaimers

1. Goes against history and common sense

2. Not for everyone

You Know You Want To

Build your own game engine!

“Reinventing the wheel”

“I get total control”

“I know exactly how everything works”

“I am more emotionally invested when it’s my own tech.”

“We can get on to more platforms faster.”

Write games, not engines

Observations

1. You can reinvent as much of the wheel as you want.

2. The Engine IS the Game

ENGINES ARE CONTENT MACHINES

Part 1:

What Makes a Great Engine?

NOT rendering physics AI

The ability of content creators to shovel content into the game as fast as possible

... and to iterate on it.

The Content Problem

“Shovel content into the game as fast possible.”

Bitmaps Audio Models Environments Animations Objects Behavior ...

???

ModelGeometry

Textures

LOD 1LOD 2LOD 3...

ColorBumpDetailSpecular...

SkeletonLOD 1LOD 2LOD 3...

Vertex weights

AIBehaviorPerceptionScript support...

AnimationsAction logic

Ragdoll

AudioFXDialogue...

Game params(~10 bajillion)

CryEngine 2

Sandbox TM / Roads and Rivers Tool

CryEngine 2

Editorfull-featured terrain editor

StorageParametric surface

RuntimeDynamically tessellated polygon-based terrain

Flexibility vs. Usability

Flexibility

Usab

ility

Universal Principles of Design – Lidwell, Holden & Butler , 2003

Generality vs. Usefulness

Generality

Usef

ulne

ss

Behavior

Your Engine

Universal Principles of Design – Lidwell, Holden & Butler , 2003

Bitmaps Licensed Engine

The Content Meta-Problem

“Shovel content into the game as fast possible.” Bitmaps Audio Models Environments Animations Objects Behavior ...

Find the Game as fast possible.(i.e. define all of the above)

MIDDLEWAREPart 2:

The Hard Bits

Reinvent as much of the wheel as necessary.

Physics Animation Scripting Pathfinding

For the rest, there’s middleware.

The Ideal

The best way to build an engine is to assemble it.

Choose your Price

Box2d, Bullet Havok Physics, PhysX

Cal3d Granny, Havok Behavior, Morpheme

GameSWF Scaleform, Iggy

Lua ... Lua?Recast, OpenSteer AI.implant, Kynapse,

Navpower

SPUTNIKPart 3:

Sputnik

Dev Time: ~ 1 year

Team size: 2

Cost: $0 (excluding labor)

ScriptClear

Maintainable

Iterable

Philosophy

Performant, Game-

agnosticExquisitely Engineered

C++

Loose

Game-specific

Sputnik

App-Layer Features

AI / A* 2d physics Embedded Flash Layer-based rendering skeletal 2d animation

Sputnik

Core Features

data-reflection component

object-model data versioning pervasive scripting C# Editor Bindings memory management performance tools XML / binary file formats in-engine Performance tools

“High-leveragetechnologies”

Sputnik

Core Features

data-reflection component

object-model data versioning pervasive scripting C# Editor Bindings memory management performance tools XML / binary file formats In-engine Performance tools

Data Reflection

Run-time information about the structure of data types Do you have a field named “foo”? What is the offset of that field from the start of the

instance? Is it read-only?

Note: Built into Java/C# Implicit in C/C++

The Big Advantage: allow type-agnostic code

Data Reflection

C++ Class(file.h)

Run-timeSchema

C# Glue

Parse(Python)

DataSerialization

VersioningLua

C# Editors

s_plane2d::x_s_plane2d_schema_handle= schema_new("s_plane2d", "");if (s_plane2d::x_s_plane2d_schema_handle.valid()){

s_schema *schema= s_plane2d::x_s_plane2d_schema_handle.get();

schema->set_initialize(s_plane2d_initialize);schema->set_erase(s_plane2d_erase);schema->add_struct_field("normal", "s_vector2d",

_read_write, 1);schema->add_struct_field("point", "s_vector2d", _read_write,

1);

schema->set_expected_size(sizeof(s_plane2d));}Note: We DON’T support

•multiple inheritence•virtual functions

Pervasive Scripting

The Goals

Everything you can do in C++, you can do in Script

To Create a Continuity between Prototyping and Production

Pervasive Scripting

We use Lua Runtime recompilation Dynamic typing

Two parts Component scripts System scripts

Hurray!2x Productivity

Kill me now

Component Scripts

A*

Perception/Ray-casting

Target selectio

n

Behavior

Physics

Animation

playback

Animation control

Squad behavi

orRando

mScript

Component Scripts

A*

Perception/Ray-casting

Target selectio

n

Behavior

Physics

Animation

playback

Animation control

Squad behavi

orRando

mScript

System Scripts

I/OBoids

Subtitles

Console

Effects

Rendering

Achievements

Missions

Random

Script

System Scripts

Missions

A Note on Script Data

Script data will need to Serialize Version Interoperate with tools

All of this suggests All script data is schematized The engine manages all script data Lua’s memory pool is transient Ancillary benefit: One lua state per source file, not

one per instance.

The Result

Systems that don’t exist in Fallen Frontier: Health / death / damage Weapons / items / equipment / powers AI Behavior HUD / UI / Menus Missions / Levels / Objectives

C# Editor Bindings

Why C#?

The best language for the job Easy, familiar, elegant Reasonably performant Massive availability of dev tools

syntax coloring, intellisense winforms

Organization Build Sputnik Core as DLL Reflection Layer in C# Reflected classes call transparently into DLL

A Word on Editors

The two most important workflow /productivity technologies ever

invented:

Copy / pasteUndo / Redo

(Hard to start with, very VERY hard to retro-fit.)

DEMO

Ideas

The Engine is the Game Game Concepts are Supported at Every

Level Flexibility vs. Usability Meta-Content: Finding the Game Tight Core vs. Loose App Layer High-Leverage Technology

Data Reflection Pervasive scripting Tools

Necessities

Time Experienced engineering Data

Serialization Versioning

Tools Don’t be afraid to go custom Optimize the critical pipelines Undo/redo Copy/paste

“Write Games Not Engines”

Yes.Don’t build in isolation

You won’t get your representations right

The Engine IS the game

Thanks!