Massive ECS - sparse set ECS with rollbacks

Made for games with deterministic prediction-rollback netcode. Currently distributed as Unity package.

Prediction-rollback netcode has very stable nature, and is mainly used in fast paced online multiplayer games, such as Overwatch and Rocket League.

Overview

This is a library, not a framework. Thus, it does not try to take control of the user codebase or the main game loop.

ECS features:

• Fast and simple ECS without any code generation
• Support сomponents of any type
• No deferred commands execution
• Garbage-free API. Make in-place queries, no caching required!
• Groups for SoA multi-component iteration (inspired by EnTT)
• Data pagination for stable resizing during iteration
• Full state serialization and deserialization
• IL2CPP friendly, tested with high stripping level on PC | Android | WebGL
• Unity integration (WIP)

Rollback features:

• Ultra-fast saving and rollbacking with cyclic buffers
• Support for components with managed data, such as arrays, strings, etc. (see the wiki)

Consider this list a work in progress as well as the project.

Code Examples

using Massive;

struct Player
{
}

struct Position
{
	public float X;
	public float Y;
}

struct Velocity
{
	public float Magnitude;
}

class Program
{
	static IRegistry CreateRegistry()
	{
		var registry = new Registry();

		for (int i = 0; i < 10; ++i)
		{
			var entity = registry.Create(new Position() { X = i * 10f });

			if (i % 2 == 0)
				registry.Assign(entity, new Velocity() { Magnitude = i * 10f });

			if (i % 3 == 0)
				registry.Assign<Player>(entity);
		}

		return registry;
	}

	static void Update(IRegistry registry, float deltaTime)
	{
		var view = registry.View();

		// Iterate using view
		view.ForEach((int entityId, ref Position position, ref Velocity velocity) =>
		{
			position.Y += velocity.Magnitude * deltaTime;

			if (position.Y > 5f)
			{
				// Create and destroy entities during iteration
				registry.Destroy(entityId);
			}
		});

		// Pass extra arguments to avoid boxing
		view.ForEachExtra((registry, deltaTime),
			(ref Position position, ref Velocity velocity,
				(IRegistry Registry, float DeltaTime) args) =>
			{
				// ...
			});

		// Make queries right in place where they are used
		// You don't have to cache anything!
		registry.View()
			.Filter<Include<Player>, Exclude<Velocity>>()
			.ForEach((ref Position position) =>
			{
				// ...
			});

		// Iterate using foreach
		foreach (var entityId in registry.View().Include<Player, Position>())
		{
			ref var position = ref registry.Get<Position>(entityId);
		}

		// Iterate manually over data set
		var velocities = registry.Components<Velocity>();
		for (int i = 0; i < velocities.Count; ++i)
		{
			ref var velocity = ref velocities.Data[i];
			// ...
		}
	}

	static void Main()
	{
		var registry = CreateRegistry();
		Update(registry, 1f / 60f);
	}
}

Note

Some APIs are subject to change, but overall the architecture is stable.

Installation

Make sure you have standalone Git installed first. Reboot after installation.
In Unity, open "Window" -> "Package Manager".
Click the "+" sign at the top left corner -> "Add package from git URL..."
Paste this: https://github.com/nilpunch/massive-ecs.git
See minimum required Unity version in the package.json file.

How it works

Each Massive data structure contains cyclic buffer in linear memory. This allows for very fast saving and rollbacking, copying the entire data arrays at once. MassiveRegistry simply uses these Massive data structures internally, so we get the simplest possible ECS with rollbacks.