GodotFlecs

A (slightly) opinionated ECS for Godot C#, built on top on Flecs and Flecs.NET. Core prinicples are providing Entity2D and WorldNode nodes that automatically register children as components. On each physics frame, the ECS world executes all systems. There are additionally nodes for other logic patterns: Script, StateMachine, and Trigger.

Nodes and components are kept in sync between the Godot Scene Tree, and the Flecs World. This means that you can use the Godot Editor to create and edit your game, and then use Flecs to add logic to your game. Adding a child node to an Entity2D will automatically add a component to the entity. Removing a child node will remove the component. Starting from Flecs also works, i.e., adding an unparented Node as a component will add it to the Godot Scene Tree.

C# Script Example

public partial class Game : WorldNode
{
  public override void _Ready()
  {
    base._Ready();

    // movement system matches on Entity2D components automatically discovered
    // and Movement components added by input detection
    World.Routine<Entity2D, Movement>()
      .Each((ref Entity2D entity2d, ref Movement movement) =>
      {
        entity2d.Position += movement.Direction * 10;
        movement.QueueFree();
      });
  }

  public override void _PhysicsProcess(double delta)
  {
    base._PhysicsProcess(delta);

    var direction = Godot.Input
      .GetVector("ui_left", "ui_right", "ui_up", "ui_down")
      .Normalized();

    if (!direction.IsZeroApprox())
    {
      // gets the Flecs `Entity` associated with the node named "Player"
      GetNode("Player")
        .GetEntity(World)
        .Set(new Movement { Direction = direction });
    }
  }
}

public partial class Movement : Node2D
{
    public Vector2 Direction { get; set; }
}

Scene

[gd_scene load_steps=3 format=3 uid="uid://gameuid"]

[ext_resource type="Script" path="res://Game.cs" id="1"]
[ext_resource type="Script" path="res://Tools/Entity2D.cs" id="2"]
[ext_resource type="Texture2D" uid="uid://textureuid" path="res://icon.svg" id="3"]

[node name="Game" type="Node2D"]
script = ExtResource("1")

[node name="Player" type="Node2D" parent="Game"]
script = ExtResource("2")

[node name="Sprite2D" type="Sprite2D" parent="Player"]
texture = ExtResource("3")

Setup

First, you'll want to copy the contents of Tools into your Godot C# project.

dotnet nuget add source https://gitlab.com/api/v4/projects/51698729/packages/nuget/index.json -n Gitlab
dotnet restore

Build and Run

dotnet build
godot

Example

This project is a Godot project, so you can open it in Godot and run it. The example is a simple game where you control a player with mouse, with a few sample systems. The potions and fire entities will invoke AreaTrigger components, while the spiders will follow the WanderScript scripting.

Super-Duper Pre-Alpha

This framework is in a very early stage. It's not ready for production use. I'm totally open to API changes. Honestly, I'm posting this publicly for feedback, so hit me up.