Entity-Tree-Component-System

ETCS (Entity-Tree-Component-System) is a small, simple and fast-ish Archetype-ECS for >= C++23.

Introduction

Features and design choices

• All exposed entities (etcs::Entity) are in reality entity "views", and the real entity data is packed in an dense array
• Worlds can always be created are stored in an hidden global world manager and can be accessed through the handle etcs::World
• A default world is created during etcs::init() and all worlds are destroyed when etcs::quit() is called
• Entities support parent-child hierarcies and lookups by default
• Cache-friendly component storage due to the archetype implementation
• Simple-to-understand and small codebase

ETCS is still quite basic right now, so it doesn't fully support more advanced features like tags, thread safety and advanced queries.

Example

#include <ETCS/ETCS.h> // includes all components of the library
#include <cstdio>

struct Position {
public:
    double x = { }, y = { };
};

struct Velocity {
public:
    double x = { }, y = { };
};

int main() {
    etcs::init();

    auto world = etcs::world();

    auto root = world.insertEntity();

    for (etcs::object_id i = 0; i < 1024; i++) {
        auto e = root.insertChild(std::to_string(i)); // use lsd::toString if you have it as a dependency
        
        if (i % 1 == 0) e.insertComponent<Position>(  // first API style: entity centric
            Position { static_cast<double>(i), static_cast<double>(i) / 2}
        );
        if (i % 2 == 0) world.insertComponent<Velocity>( // second API style: world centric
            e, Velocity { static_cast<double>(i * i), static_cast<double>(i) / 3}
        );
        if (i % 3 == 0) e.disable();
    }

    for (auto [e, v, p] : world.query<etcs::Entity, const Velocity, Position>()) {
        p.x += v.x;
        p.y += v.y;

        std::printf("Hello, Entity number %s at position (%.0f, %.0f)!\n", e.name().data(), p.x, p.y);
    }

    etcs::quit();
}

Integration using CMake

This project was designed to be used with CMake. Other build systems have not been tested.

Basic linkage

Adding the Library as a CMake dependency defines the targets ETCS::ETCS-<build_type> and ETCS::Headers, which you can link to your project.

You can set the build type by configuring the option ETCS_STATIC

Optional dependencies and extensions

ETCS was designed to be used with the Lyra-Standard-Library, although it can be used without it, since the required structures have been seperatly implemented using the standard library. You can include LSD in your base project and add it as a CMake depdendency before adding ETCS so that it can be found.

ETCS also has some basic premade components available by default, although they require GLM as a dependency and have to be enabled by setting the CMake option ETCS_ENABLE_COMPONENTS_EXT (you can find it in the CMakeLists.txt).

Contributing

If you find anything you can contribute about the project, you can just open an issue or a PR, although I can't guarantee that I will respond to it, since this project is not my main focus, but everybody is welcome.