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

Dec 05, 2023 188 likes •1.5k views

The computing scientists 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

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“The computing scientist’s main challenge is not to get confused by the complexities of their

  • wn making. ”
  • E. W. Dijkstra
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Entity-Component

Systems + You

(They're not just for games anymore)

@parisba | @The_McJones | @TheMartianLife 2
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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
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ECS?

@parisba | @The_McJones | @TheMartianLife 6
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If you Google ECS, you'll probably get Unity, or Amazon.

Or something entirely unrelated.

Sorry. @parisba | @The_McJones | @TheMartianLife 7
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This is not a games talk!

Mostly. @parisba | @The_McJones | @TheMartianLife 8
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Before we start..

Is anyone using ECS, or working in games? @parisba | @The_McJones | @TheMartianLife 9
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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
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What is ECS?

@parisba | @The_McJones | @TheMartianLife 11
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Entity Component Systems

@parisba | @The_McJones | @TheMartianLife 12
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SLIDE 13 There's the short answer, and the long answer... @parisba | @The_McJones | @TheMartianLife 13
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ECS?!

@parisba | @The_McJones | @TheMartianLife 14
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Strict separation between data and logic

@parisba | @The_McJones | @TheMartianLife 15
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Oh, ECS...

@parisba | @The_McJones | @TheMartianLife 16
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The Impetus

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

(you've only got ~16.6 milliseconds)

@parisba | @The_McJones | @TheMartianLife 18
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Flexibility

(with jillions of objects and factors)

@parisba | @The_McJones | @TheMartianLife 19
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ECS encourages both

Performance + Flexibility

@parisba | @The_McJones | @TheMartianLife 20
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The key word being 'encourages'

You can, of course, mess it up. @parisba | @The_McJones | @TheMartianLife 21
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So what?

Everything is fine already! @parisba | @The_McJones | @TheMartianLife 22
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It's a bit messy.

@parisba | @The_McJones | @TheMartianLife 26
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God Objects

@parisba | @The_McJones | @TheMartianLife 27
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History Lesson!

@parisba | @The_McJones | @TheMartianLife 29
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Early 'ECS'

@parisba | @The_McJones | @TheMartianLife 30
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Adam Martin's ECS

» Entities have IDs » Components have data » Systems have logic @parisba | @The_McJones | @TheMartianLife 32
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Let's look at these

  • ne by one...
@parisba | @The_McJones | @TheMartianLife 33
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Entity

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

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

Just a thing to reference. @parisba | @The_McJones | @TheMartianLife 36
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Isn't this just a primary key?

@parisba | @The_McJones | @TheMartianLife 37
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Yes, yes it is.

@parisba | @The_McJones | @TheMartianLife 38
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Components

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

Also pretty boring.

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

@parisba | @The_McJones | @TheMartianLife 41
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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
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ECS or EC?

@parisba | @The_McJones | @TheMartianLife 43
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ECS in use today

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It's very popular.

In games.

@parisba | @The_McJones | @TheMartianLife 45
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To do this...

@parisba | @The_McJones | @TheMartianLife 46
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We're gonna talk about games. Sorry.

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Games are very dynamic

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Game worlds are built out of entities

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A tree is different from a human who is different from an alien who is different from...

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Games are in constant development flux

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games are made up of moving parts

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But...

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There is common pool of aspects

» Position data » Visuals data » Animation data » Sound data » Gameplay data @parisba | @The_McJones | @TheMartianLife 56
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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
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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
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Separating data from behaviour

@parisba | @The_McJones | @TheMartianLife 59
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Objects?

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Objects and (rigid, mostly) class hierarchies

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Complex hierarchies

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Composition, not Inheritance

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Composing entities

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Composing entities

Benefits:
  • 1. Easy to add new entities.
  • 2. Easy to change entities.
  • 3. Performant!
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ECS and Games, now

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Entity

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Entity

Examples:
  • Crate
  • Ball
  • Enemy
  • Player
  • Traffic light
@parisba | @The_McJones | @TheMartianLife 70
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Component

@parisba | @The_McJones | @TheMartianLife 71
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Component Examples

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

@parisba | @The_McJones | @TheMartianLife 73
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System Examples

» player control » render » gravity » movement » AI control @parisba | @The_McJones | @TheMartianLife 74
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Games, Games, Games

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ECS doesn't necessarily mean less code.

Theoretically it means better code, though. @parisba | @The_McJones | @TheMartianLife 76
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What ECS is good for

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Performance?

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“The purpose of all programs, and all parts of those programs, is to transform data from

  • ne form to another.”
Mike Acton
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Data Oriented Design

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Data-oriented Design is tricky

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You never do just

  • ne thing
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Cache Misses

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Cache misses

suck

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Data-oriented Design = Programming for Good Memory Access

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ECS encourages Data-

  • riented Design
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Caches, memory speed, oh my!

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Parallelisation

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Lots of tasks. Large set of data.

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Structure around consuming data as a stream.

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Complex, interlocking systems.

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Composability

The biggest advantage

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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
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GUI Programming

@parisba | @The_McJones | @TheMartianLife 98
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A NEAT SIDE-EFFECT OF ECS!

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In practice, it's not that easy...

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What ECS is not good for

» Disk heavy operations » Unchanging data and procedures » Heavily hierarchical data @parisba | @The_McJones | @TheMartianLife 101
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How would you go about

making an ECS?

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Quick and Dirty way

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Start with our entities

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SLIDE 105 entities int[] = [0,1,2,3,4,5...] /* player skeleton with sword skeleton with shield camera etc etc */ @parisba | @The_McJones | @TheMartianLife 105
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now we need some components

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SLIDE 107 TransformComponent { position rotation scale } MovementComponent { speed direction } HealthComponent { life } ShieldComponent { reduction } DamageComponent { damage target } RenderComponent { mesh textures } PlayerComponent {} CameraComponent {} @parisba | @The_McJones | @TheMartianLife 107
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how do we connect entities and components?

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SLIDE 109 Game { // all our entities... entities int[] = [0,1,2,3,4,5...] // all of these are of size entities long damages DamageComponent[] transforms TransformComponent[] renders RenderComponent[] movers MovementComponent[] healths HealthComponent[] shields ShieldComponent[] players PlayerComponent[] cameras CameraComponent[] @parisba | @The_McJones | @TheMartianLife 109
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SLIDE 110 damages = [nil, 1, 1, 3, 3, 1, nil] healths = [100, 5, 5, 5, 5, 5, nil] @parisba | @The_McJones | @TheMartianLife 110
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What about the systems?

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SLIDE 112 updateFrame(deltaTime) { // first we get user input and use that to update player position input = getInput() updatePlayerSpeed(input, players) // then move everything that can be moved // including the player moveEntities(movers, transforms, deltaTime) // then we deal damage damageEntities(damages, healths) // then we reduce damage for everyone with shields reduceDamage(shields, healths) // then we render the frame renderFrame(renders, transforms, cameras) } @parisba | @The_McJones | @TheMartianLife 112
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SLIDE 113 moveEntities(movers, transforms, deltaTime) { for mover, transform in movers, transforms { transform.position += mover.velocity * deltaTime } } @parisba | @The_McJones | @TheMartianLife 113
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It gets better, of course

This approach isn't the best for large scale, but its the simplest way to get started. @parisba | @The_McJones | @TheMartianLife 116
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Existing

implementations

@parisba | @The_McJones | @TheMartianLife 117
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ECS implementations

» Rust (Specs): https://github.com/slide-rs/specs » C++ (EnTT): https://github.com/skypjack/entt » Elixir: https://github.com/yosriady/ecs » C# (Entitas): https://github.com/sschmid/Entitas-CSharp » Java (Artemis): http://gamadu.com/artemis/ » C# (EgoCS): https://github.com/andoowhy/EgoCS » C++ (EntityX): https://github.com/alecthomas/entityx » C++ (Anax): https://github.com/miguelmartin75/anax » ...and many, many more! @parisba | @The_McJones | @TheMartianLife 118
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None of this is new.

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Summary

@parisba | @The_McJones | @TheMartianLife 120
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Entities Components Systems

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ECS = Composable

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ECS is composition

  • n steroids
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Data-oriented Design

@parisba | @The_McJones | @TheMartianLife 124
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Strengths

» Performance (hopefully) » Flexibility » No heirarchy to remember » Systems have many of the advantages of microservices/functional programming @parisba | @The_McJones | @TheMartianLife 125
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Weaknesses

» More code upfront » Harder to keep everything in your head » No clear starting point @parisba | @The_McJones | @TheMartianLife 126
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Pick and choose the ideas you like

There is no one 'right way'. @parisba | @The_McJones | @TheMartianLife 127
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Resources

» Slides will go up on the SACon website shortly » Talk resources can be found at https://lab.to/SAConNYC19Resources @parisba | @The_McJones | @TheMartianLife 128
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Review us!

@parisba | @The_McJones | @TheMartianLife 129
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Thank you!

» Find us online: » @parisba » @The_McJones » @TheMartianLife » Chat with us at 'Meet the Experts'! 3:05PM today! Sponsor Pavilion! Come and tell us we're wrong! » Stay warm + enjoy the rest of your #OReillySACon <3 @parisba | @The_McJones | @TheMartianLife 130