Met ECS

A simple Entity Component System library made for learning purposes. It is header-only, so just have to copy the content of the src folder and include <met/met.hpp> to check it out. It does require a C++ 17 version of your compiler though.

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Made by students, the project purposes are to be easy to understand and thoroughly documented. It is seen as an entry point for users and developers. We provide both a post-mortem to explain the inner-working of the library, and many exercices to get started with ECS.

The API is heavly based on ENTT by skypjack, you should check it out if you're looking for a highly performant and production-ready library.

Violets are blue, roses are red, and when I met ecs, my world rebooted 🌐

Table of Contents

• Introduction
  • What is ECS ?
  • Code Example
• Learn
  • Use an ECS library
  • Create an ECS library
• Build unit tests
• External links
  • FAQs
  • Videos
  • Articles
  • Libraries

Introduction

What is ECS ?

ECS (Entity Component System) is way to organize your data and your logic which radicaly changes from traditional Object-Oriented Programming. It is seen as both a way to improve performance and to ease maintenance. Well-suited for games, it is designed to handle operations on large groups.

ECS is made out of 3 pieces that can be summarized with these simple rules :

• Entities are unique identifiers
• Components are plain datatypes (Positions, Colors, etc...)
• Entities can possess zero or more components
• Systems are logic executed on entities with matching component sets

Code Example

#include <met/met.hpp>

struct Position {
    float x;
    float y;
};

struct Velocity {
    float dx;
    float dy;
};

int main() {
    met::registry registry;
    auto entity = registry.create();
    
    Position pos = { 2, 3 };
    registry.assign<position>(entity, pos);
    
    Velocity vel = { 5, 8 };
    registry.assign<position>(entity, vel);
    
    registry.view<Position, Velocity>().each([](met::entity id, Position& pos, Velocity& vel) {
        pos.x += 2;
        std::cout << "pos " << pos.x << " " << pos.y << std::endl;
        std::cout << "vel " << vel.dx << " " << vel.dy << std::endl;
    });

    // ...
}

Learn

Use an ECS library

Some exercices has been created to use ECS step by step.

Create an ECS library

The post-mortem offers a view on ECS possible implementations and explain everything there is to know about this library.

Build unit tests

Prerequisites

You need to have CMake and a C++ compiler which handles C++ 17.

Linux

sudo apt-get install build-essential cmake

Windows

You can install Visual Studio to get the MSVC compiler, and you can download CMake from their website.

External links

FAQs

• SanderMertens ECS
• Awesome list ECS by jslee02

Videos

Articles

Libraries

• ENTT
• ECS by redxdev