Flecs is a fast and lightweight Entity Component System for C89 / C99 / C++11 that packs a lot of punch in a small footprint:
- Blazing fast iteration speeds with direct access to raw C arrays across multiple components
- Support for hierarchies, prefabs, traits, state machines, snapshots and more
- An efficient lock-free architecture allows for modifying entities across multiple threads
- Queries with builtin support for sorting, change tracking, read-write permissions and more
- Systems that are time triggered, rate triggered, run every frame or run only when needed
- A customizable core that lets you include only the features you need
This is Flecs v2, which is a breaking change from v1. For the last v1 release, see: https://github.com/SanderMertens/flecs/releases/tag/v1.3
If you have questions, suggestions or a Flecs project you'd like to show off, join the Flecs Discord!
ECS (Entity Component System) is a design pattern often found in gaming and simulation which produces code that is fast and reusable. Dynamic omposition is a first-class citizen in ECS, and there is a strict separation between data and behavior. A framework is an Entity Component System if it:
- Has entities that are unique identifiers
- Has components that are plain data types
- Has systems which are behavior matched with entities based on their components
See Docsforge for a more readable version of the documentation.
This is a simple flecs example in the C++11 API:
struct Position {
float x;
float y;
};
struct Velocity {
float x;
float y;
};
int main(int argc, char *argv[]) {
flecs::world ecs;
ecs.system<Position, const Velocity>()
.each([](flecs::entity e, Position& p, const Velocity& v) {
p.x += v.x * e.delta_time();
p.y += v.y * e.delta_time();
std::cout << "Entity " << e.name() << " moved!" << std::endl;
});
ecs.entity("MyEntity")
.set<Position>({0, 0})
.set<Velocity>({1, 1});
while (ecs.progress()) { }
}The easiest way to add Flecs to a project is to add flecs.c and flecs.h to your source code. These files can be added to both C and C++ projects (the C++ API is embedded in flecs.h). Alternatively you can also build Flecs as a library by using the cmake, meson, bazel or bake buildfiles.
The Flecs source has a modular design which makes it easy to strip out code you don't need. At its core, Flecs is a minimalistic ECS library with a lot of optional features that you can choose to include or not. This section of the manual describes how to customize which features to include.
The following modules are available in flecs-hub and are compatible with v2:
| Module | Description |
|---|---|
| flecs.meta | Reflection for Flecs components |
| flecs.json | JSON serializer for Flecs components |
| flecs.rest | A REST interface for introspecting & editing entities |
| flecs.player | Play, stop and pause simulations |
| flecs.dash | Web-frontend for remote monitoring and debugging of Flecs apps |
| flecs.components.input | Components that describe keyboard and mouse input |
| flecs.components.transform | Components that describe position, rotation and scale |
| flecs.components.physics | Components that describe physics and movement |
| flecs.components.geometry | Components that describe geometry |
| flecs.components.graphics | Components used for computer graphics |
| flecs.components.gui | Components used to describe GUI components |
| flecs.components.http | Components describing an HTTP server |
| flecs.systems.transform | Hierarchical transforms for scene graphs |
| flecs.systems.sdl2 | SDL window creation & input management |
| flecs.systems.sokol | Sokol-based renderer |
| flecs.systems.civetweb | A civetweb-based implementation of flecs.components.http |