The computing scientists main challenge is not to get confused by - PowerPoint PPT Presentation

“The computing scientist’s main challenge is not to get confused by the complexities of their own making. ” E. W. Dijkstra

Entity-Component Systems + You ( They're not just for games anymore ) @parisba | @The_McJones | @TheMartianLife 2

Hello! » Paris (@parisba) » Game developer, PhD Computing, Author » Tim (@The_McJones) » Game developer, PhD Computing, Author » Mars (@TheMartianLife) » Software developer, Research & Teaching Assistant, Upcoming Author @parisba | @The_McJones | @TheMartianLife 3

ECS? @parisba | @The_McJones | @TheMartianLife 6

If you Google ECS, you'll probably get Unity, or Amazon. Or something entirely unrelated. Sorry. @parisba | @The_McJones | @TheMartianLife 7

This is not a games talk! Mostly. @parisba | @The_McJones | @TheMartianLife 8

Before we start.. Is anyone using ECS, or working in games? @parisba | @The_McJones | @TheMartianLife 9

Overview » What is ECS? » History Lesson » ECS Implementations » What ECS is good for » What ECS is not good for » Summary @parisba | @The_McJones | @TheMartianLife 10

What is ECS? @parisba | @The_McJones | @TheMartianLife 11

Entity Component Systems @parisba | @The_McJones | @TheMartianLife 12

There's the short answer, and the long answer... @parisba | @The_McJones | @TheMartianLife 13

ECS?! @parisba | @The_McJones | @TheMartianLife 14

Strict separation between data and logic @parisba | @The_McJones | @TheMartianLife 15

Oh, ECS... @parisba | @The_McJones | @TheMartianLife 16

The Impetus Games really only have two needs: » performance » flexibility @parisba | @The_McJones | @TheMartianLife 17

Performance (you've only got ~16.6 milliseconds) @parisba | @The_McJones | @TheMartianLife 18

Flexibility (with jillions of objects and factors) @parisba | @The_McJones | @TheMartianLife 19

ECS encourages both Performance + Flexibility @parisba | @The_McJones | @TheMartianLife 20

The key word being 'encourages' You can, of course, mess it up. @parisba | @The_McJones | @TheMartianLife 21

So what? Everything is fine already! @parisba | @The_McJones | @TheMartianLife 22

It's a bit messy. @parisba | @The_McJones | @TheMartianLife 26

God Objects @parisba | @The_McJones | @TheMartianLife 27

History Lesson! @parisba | @The_McJones | @TheMartianLife 29

Early 'ECS' @parisba | @The_McJones | @TheMartianLife 30

Adam Martin's ECS » Entities have IDs » Components have data » Systems have logic @parisba | @The_McJones | @TheMartianLife 32

Let's look at these one by one... @parisba | @The_McJones | @TheMartianLife 33

Entity » an object in your game, uh, software » anything, really, a player, an enemy, anything » an identifier, no logic @parisba | @The_McJones | @TheMartianLife 34

Entity Two excellent descriptions of an entity (in games): » everything but the terrain » assemblages @parisba | @The_McJones | @TheMartianLife 35

Entities are boring. Just a thing to reference. @parisba | @The_McJones | @TheMartianLife 36

Isn't this just a primary key? @parisba | @The_McJones | @TheMartianLife 37

Yes, yes it is. @parisba | @The_McJones | @TheMartianLife 38

Components » it has some data @parisba | @The_McJones | @TheMartianLife 39

Components Also pretty boring. A flag that may also hold raw data for one aspect of a thing. @parisba | @The_McJones | @TheMartianLife 40

System @parisba | @The_McJones | @TheMartianLife 41

Systems are the interesting bit. Logic that runs continuously and performs actions on every Entity that has a Component of the aspect the System is designed to work with. @parisba | @The_McJones | @TheMartianLife 42

ECS or EC? @parisba | @The_McJones | @TheMartianLife 43

ECS in use today @parisba | @The_McJones | @TheMartianLife 44

It's very popular. In games. @parisba | @The_McJones | @TheMartianLife 45

To do this... @parisba | @The_McJones | @TheMartianLife 46

We're gonna talk about games. Sorry. @parisba | @The_McJones | @TheMartianLife 47

Games are very dynamic @parisba | @The_McJones | @TheMartianLife 48

Game worlds are built out of entities @parisba | @The_McJones | @TheMartianLife 49

A tree is different from a human who is different from an alien who is different from... @parisba | @The_McJones | @TheMartianLife 50

Games are in constant development flux @parisba | @The_McJones | @TheMartianLife 51

@parisba | @The_McJones | @TheMartianLife 52

@parisba | @The_McJones | @TheMartianLife 53

games are made up of moving parts @parisba | @The_McJones | @TheMartianLife 54

But... @parisba | @The_McJones | @TheMartianLife 55

There is common pool of aspects » Position data » Visuals data » Animation data » Sound data » Gameplay data @parisba | @The_McJones | @TheMartianLife 56

What a game seems like 1.Player presses walk forward 2.Move the player forward 3.Check if enemy can see the player avatar 4.Move towards the player 5.If in range swing sword 6.Deal damage to the player @parisba | @The_McJones | @TheMartianLife 57

What a game is actually doing 1.Receive user input 2.Raycast from enemy to player avatar 3.Update avatar and enemy position 4.Deal damage 5.Update animations 6.Render frame @parisba | @The_McJones | @TheMartianLife 58

Separating data from behaviour @parisba | @The_McJones | @TheMartianLife 59

Objects? @parisba | @The_McJones | @TheMartianLife 60

Objects and (rigid, mostly) class hierarchies @parisba | @The_McJones | @TheMartianLife 61

Complex hierarchies @parisba | @The_McJones | @TheMartianLife 62

Composition, not Inheritance @parisba | @The_McJones | @TheMartianLife 64

Composing entities @parisba | @The_McJones | @TheMartianLife 65

Composing entities Benefits: 1. Easy to add new entities. 2. Easy to change entities. 3. Performant! @parisba | @The_McJones | @TheMartianLife 66

ECS and Games, now @parisba | @The_McJones | @TheMartianLife 68

Entity @parisba | @The_McJones | @TheMartianLife 69

Entity Examples: - Crate - Ball - Enemy - Player - Traffic light @parisba | @The_McJones | @TheMartianLife 70

Component @parisba | @The_McJones | @TheMartianLife 71

Component Examples » position (an x and a y) » velocity » sprite(s) » health value » character name » player (tag) @parisba | @The_McJones | @TheMartianLife 72

System @parisba | @The_McJones | @TheMartianLife 73

System Examples » player control » render » gravity » movement » AI control @parisba | @The_McJones | @TheMartianLife 74

Games, Games, Games @parisba | @The_McJones | @TheMartianLife 75

ECS doesn't necessarily mean less code. Theoretically it means better code, though. @parisba | @The_McJones | @TheMartianLife 76

What ECS is good for @parisba | @The_McJones | @TheMartianLife 77

Performance? @parisba | @The_McJones | @TheMartianLife 78

“The purpose of all programs, and all parts of those programs, is to transform data from one form to another.” Mike Acton

Data Oriented Design @parisba | @The_McJones | @TheMartianLife 80

Data-oriented Design is tricky @parisba | @The_McJones | @TheMartianLife 81

You never do just one thing @parisba | @The_McJones | @TheMartianLife 82

Cache Misses @parisba | @The_McJones | @TheMartianLife 86

Cache misses suck @parisba | @The_McJones | @TheMartianLife 87

Data-oriented Design = Programming for Good Memory Access @parisba | @The_McJones | @TheMartianLife 89

ECS encourages Data- oriented Design @parisba | @The_McJones | @TheMartianLife 90

Caches, memory speed, oh my! @parisba | @The_McJones | @TheMartianLife 91

Parallelisation @parisba | @The_McJones | @TheMartianLife 92

Lots of tasks. Large set of data. @parisba | @The_McJones | @TheMartianLife 93

Structure around consuming data as a stream. @parisba | @The_McJones | @TheMartianLife 94

Complex, interlocking systems. @parisba | @The_McJones | @TheMartianLife 95

Composability The biggest advantage @parisba | @The_McJones | @TheMartianLife 96

ECS is great for... » GUI Programming » Editors » Audio systems » VFX systems » Simulations » A service registry » ... almost anything that's event-driven » ... anything you want to easily unit test @parisba | @The_McJones | @TheMartianLife 97

GUI Programming @parisba | @The_McJones | @TheMartianLife 98

A NEAT SIDE-EFFECT OF ECS! @parisba | @The_McJones | @TheMartianLife 99

In practice, it's not that easy... @parisba | @The_McJones | @TheMartianLife 100