Jozi.JS 2019, 21 Nov 2019

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From YouTube: Entity Component Systems - Nico Schoeman

Description

In this talk I will cover a bit of the what, how, and why of the Entity Component Systems (ECS) architecture, its focus on data oriented design, and its rapid adoption within the game industry. I will also talk over some pros and cons to entity component systems that I have run into and demo the new ecsy package, "a highly experimental Entity Component System for the web" JavaScript implementation of the entity component system pattern from the Mozilla mixed reality team. I hope you are as excited as I am!

This talk was recorded at the Jozi.JS meetup group on 21 November 2019.

https://www.meetup.com/Jozi-JS/events/266202004/

Disclaimer: The opinions in this talk are those of the individual and do not necessarily represent those of this channel, the meetup group, or its sponsors.

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Hello, everyone I said I am niku and I come from the land of gamedev I'm, also I'm, also currently on the R&D team here at BBD and I'm, a cultivator of the beer, also a connoisseur of good coffee and a companion to all puppies, and you can't see it really there, but you should take everything. I say with a grain of salt.

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Today, I'm going to talk to you about entity component systems, change for I will call it e CS I'll tell you what ECS is why it's awesome, why it sucks and how you can get started with it on your own projects, but first we must identify the problem that ETS is trying to solve game. Def is dominated by over, which is not a problem in itself, but it does lead to the rise of two other problems, namely random memory access patterns and cache misses.

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In my opinion, it also causes you to write some inflexible code via inheritance hierarchies.

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So we see CS is one of the options you have to solve those problems. It is worth noting, however, that ECS is not a library, its architectural pattern. It's also a way to organize and process data. These three main parts, the CS as the name suggests, entities, components and systems.

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Ecs is very common in games and simulations especially now since big engines such as unity, has made a perfect to implement more pure versions of ECS to benefit from the performance benefits.

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It's also been claimed to be the future of MMO games or multiplayer online for Jerry's benefit.

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However, ECS is not a silver bullet and we'll get into it later.

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One of the core concepts of ECS is data. Oriented design- and this is the dictionary definition, sort of of dot or InDesign dot or InDesign is an approach intended to maximize the locality of reference by organizing data according to how it's traversed in various stages of a program, ECS focuses heavily on data and the aim is to write sequential a modulus chunks of data that can be sequentially as much as possible. Be read and minimize cache misses that way.

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So the benefits of ECS this code, decoupling through the way that its systems are structured. Obviously the blocks of homogeneous daata, eak CSS, also scalable. You can easily extend refactor and debug your code, thus clear context within your systems, as you know what author to expect and what entities will be working or processing with that system.

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Serialization is made easier VCS, because entities are just collections of data.

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Paralyzation is also made easy because you can just take a system and put it into a separate thread and it works.

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Ecs is as generic as you can make it. Let's just total and you just just generic some of the drawbacks of EEZs. The workflow can be slower at first, because it's unfamiliar and you often need a paradigm shift.

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Unfamiliar ECS can also be challenging to interface with existing code bases.

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There are some limited use cases for ECS you're, mostly going to use it in games and simulations especially big ones that have lots of things in it.

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Ecs doesn't really have thought hiding unless you specifically go and work to do that yeah, so the entities of ECS, they're, just containers of components and are usually just a unique ID.

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The aim of entities are to have no dangling references when you destroy them. It's an example of entity. So it's just a thing for some components: components of ecs.

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They have no logic, they just start on an example of that is, if we add a health component to this entity, we're making it mortal because our health system will pick it up and immediately start processing on it systems there, the logic of our program and a container state, or ideally they shouldn't the self-contained and decoupled from other systems as much as possible, and they know what data to expect through either queries or filters they use and they follow the separation of concerns.

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Patent systems, don't care what the entirety of the entity looks like.

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They only care about the relevant parts that they're querying for so this system. Here the render system is querying for entities that have both the position and the mesh component to it. So this is this entity, but it doesn't care about the health at all.

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So now, I'm going to show you, but about Xing, but first XE is a new experimental EGS for the web from the Mozilla mixed reality. Team.

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Okay, so here I've, a very simple HTML file: I've just set up a canvas and some styling in it and the script module.

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So when working with XE first thing as we do, we import XE I'm just using a link, but it's also available on NPN, whatever package system you like, and then we need to just set up the canvas so that we can get screen sizes and contexts to actually draw things.

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And now we start with component.

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This one is just a position and you'll notice that I am using this helper function called create component class, which does all the hard work for you and sets up the whole object. It sets up reset functions and stuff like that. So it's your component can actually benefit from object, pooling.

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Oops it's gonna break later now and.

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Then it's the Ranger system right its Ranger systems a little bit more. So, let's break it down. The Ranger system is just a class, and it has this query down here which indicates that it's looking for all component or all entities that have a position component on it and it has this execute function which gets call to make the system execute. This system is just iterating through all the entities to be found in our query and drawing a circle wherever our position is like. So then we just need to set up the world.

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So most ECA systems run off this world object, which is a container of your entities and new systems. You can have multiple of them if you like. You also register your systems like this onto your world.

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However, we don't need that one now, so we're just going to render- and we also don't need this component here- I'm just creating 100 entities with position, components, random positions and I'm, using a set interval for simplicity sake just to make the world execute. You can use things like request, animation frame to make things a bit better and you can actually use Delta time and stuff like that.

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So yeah, let's get this.

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It's running and we go so we have a bunch of dots being drawn. It's not all that exciting. So, let's add some movement to it.

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First thing: first, we need a velocity, so, let's go add another component.

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There we go, which is pretty much the same as the position, it's just a vector and then we need to add the movement system.

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This one's a little bit more complex queries for entities that have both a velocity and the position and I'm using this gate. Mutable component function here, which indicates to EXCI that I'm actually going to change thoughts, are within these components and I'm just making them move based on the velocity and bouncing them when they exit the canvas.

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And then we need to register that system on here.

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Right, it's worth noting also that systems execute and the order that you registered and on to this world, and then we need to add back the salasi component over here, just giving it a random velocity. And now we should have some moving dots, yay.

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So, in conclusion, the takeaways are that ECS is great at high-volume processing of data when you have games and simulations such as strategy games, bullet hell, games, crowd, simulations anything that has a lot of entities and things moving around and doing stuff.

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Consider ECAs if performance is key within your game or your project, if performance isn't really that much of an issue for you, maybe ECS isn't really the solution. You should be looking for as easy as may get in the way of anything that has more complex or unique behaviors the cover there will tell me about character, controllers and things like that.

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Yeah does anyone have questions.