Flecs is a fast and lightweight Entity Component System with a focus on high performance game development:
- Easy to integrate, fast to compile with core that is entirely written in C99
- Includes C++11 API that enforces type safety & tightly integrates with modern C++ idioms
- Provides (SoA) access to raw component arrays for optimal cache efficiency and vectorization
- Archetype-storage with unique graph-based design enables high performance entity mutations
- Flexible API primitives allow for efficient implementation of prefabs, runtime tags and entity graphs
- Supports advanced queries that are evaluated offline so no searching is performed in the main loop
- Lockless threading design allows for efficient execution of systems on multiple threads
ECS (Entity Component System) is a design pattern often found in gaming and simulation which produces code that is fast and reusable. Dynamic composition 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 |