flecs VS bevy

I've also been enjoying building My First Game™ in Bevy using ECS. The community around Bevy really shines, but Flecs (https://github.com/SanderMertens/flecs) is arguably a more mature, open-source ECS implementation. You don't get to write in Rust, though, which makes it less cool in my book :)

I'm not very proud of the code I've written because I've found writing a game to be much more confusing than building websites + backends, but, as the author notes, it certainly feels more elegant than OOP or globals given the context.

I'm building for WASM and Bevy's parallelism isn't supported in that context (yet? https://github.com/bevyengine/bevy/issues/4078), so the performance wins are just so-so. Sharing a thread with UI rendering suuucks.

If anyone wants to browse some code or ask questions, feel free! https://github.com/MeoMix/symbiants

Flecs does just that: https://ajmmertens.medium.com/why-it-is-time-to-start-thinking-of-games-as-databases-e7971da33ac3

I'm trying to optimize my workflow as much as possible, and came across this thing called an ECS. After doing a little bit more digging I found some decent guides on how you would make one, I also found one premade called FLECS. FLECS is nice and all, but I was looking for something more simple that just has the bare bones of what I need and is also configurable. I haven't been able to really find anything like that, so I was wondering if anyone had an example of maybe their way of implementing an ECS. I know how to go about it, but I'm unsure of exactly what the code would look like.

Since we wanted a common game simulation that would be on both the server and the client we looked into a few libraries that would fit our ECS needs. It was decided we were going to write this common part of our game in C++, but rust was considered. C++ was a familiar language for us so naturally EnTT and flecs came up right away. I had used EnTT before, writing some small demo projects, so our choice was made based on familiarity. In order to integrate with Unity we created a small C interface to communicate between our simulation code and Unity’s C#. Here’s close to what it looked like. I removed some parts for brevity sake.

Repository: https://github.com/SanderMertens/flecs

This is the project: https://github.com/SanderMertens/flecs (query engine implementation lives here: https://github.com/SanderMertens/flecs/tree/master/src/addons/rules)

There's also a performance question. While we can now use Blueprint nativization to convert Blueprints to C++ the result will be a fairly naive version, fast enough for most purposes but not if you're trying to push every bit of performance. This is where you're looking at making sure you're hitting things such as using the CPU cache as well as possible for an ECS system (Look at ENTT or Flecs if you want to see what they're about and why you'd want one), or a system needing to process massive amounts of data quickly such as the Voxel Plugin.

If I knew C++ and I'd heard about it before I started my current project, I would have been tempted to use this https://github.com/SanderMertens/flecs which can be built to WASM. Of course you still need JavaScript in the front end to link to the WASM part. I've recently been using esbuild to bundle my front end code, which does a pretty similar job to webpack, but is a bit faster.

When do think bevy will support entity-entity relationships ? https://github.com/bevyengine/bevy/issues/3742.

Flecs ECS already supports this: https://github.com/SanderMertens/flecs/blob/master/docs/Rela...

For a modern engine you’re probably best looking at Unity’s DOTS. You may also want to check out some of the different open source ECS libraries such as flecs and EnTT are two popular ones for C++, but there’s lots of them. Largely you’ll see lots of different approaches taken, all with their own pros and cons. Not all of them will be performant (some focus more on the design benefits) while others will be optimised for certain use cases. What you should prioritise will depend on your specific needs.

Missing one of the best choices as long as "maturity" isn't on the top of your list: Bevy - https://bevyengine.org/

Game engine written in Rust, leveraging ECS in almost every place and way, with a really capable WASM export option. Wrestling ECS for the first time might take you some time, but in my experience helps you keep game code as clean and decoupled as game code could be.

I don't see WASM/WebGPU changing anything when it comes to gaming, as an industry, personally. 3d visualizations and interactive websites? Yeah definitely a nice improvement over WebGL 2, if years late.

WebGPU is pretty far behind what AAA games are using even as of 6 years ago. There's extra overhead and security in the WebGPU spec that AAA games do not want. Browsers do not lend themselves to downloading 300gb of assets.

Additionally, indie devs aren't using Steam for the technical capabilities. It's purely about marketshare. Video games are a highly saturated market. The users are all on Steam, getting their recommendations from Steam, and buying games in Steam sales. Hence all the indie developers publish to Steam. I don't see a web browser being appealing as a platform, because there's no way for developers to advertise to users.

That's also only indie games. AAA games use their own launchers, because they don't _need_ the discoverability from being on Steam. So they don't, and avoid the fees. If anything users _want_ the Steam monopoly, because they like the platform, and hate the walled garden launchers from AAA companies.

(I work on high end rendering features for the Bevy game engine https://bevyengine.org, and have extensive experience with WebGPU)

I was working through an example in the repo for the Bevy game engine recently and came across this code

That's possible. I did spend quite a bit of time tinkering with compiler flags, and followed the recommendations.

Some notes I found just now seems to agree with my results, though: https://github.com/bevyengine/bevy/issues/3978#issuecomment-...

I cannot recommend immediate mode GUI programming based on the limitations I've experienced working with egui.

egui does not support putting two widgets in the center of the screen: https://github.com/emilk/egui/issues/3211

It's really easy to get started with immediate mode, it's really easy to bust out some UI, but the second you start trying to involve dynamically resized context and responsive layouts -- abandon all hope. The fact it has to calculate everything in a single pass makes these things hard/impossible.

... that said, I'm still using it for https://ant.care/ (https://github.com/MeoMix/symbiants) because it's the best thing I've found. I'm crossing my fingers that Bevy's UI story (or Kayak https://github.com/StarArawn/kayak_ui) become significantly more fleshed out sooner rather than later. Bevy 0.13 should have lots more in this area though (https://github.com/bevyengine/bevy/discussions/9538)

I've also been enjoying building My First Game™ in Bevy using ECS. The community around Bevy really shines, but Flecs (https://github.com/SanderMertens/flecs) is arguably a more mature, open-source ECS implementation. You don't get to write in Rust, though, which makes it less cool in my book :)

I'm not very proud of the code I've written because I've found writing a game to be much more confusing than building websites + backends, but, as the author notes, it certainly feels more elegant than OOP or globals given the context.

I'm building for WASM and Bevy's parallelism isn't supported in that context (yet? https://github.com/bevyengine/bevy/issues/4078), so the performance wins are just so-so. Sharing a thread with UI rendering suuucks.

If anyone wants to browse some code or ask questions, feel free! https://github.com/MeoMix/symbiants

These days, some game engines have done pretty well at making compute shaders easy to use (such as Bevy [1] -- disclaimer, I contribute to that engine). But telling the scientific/financial/etc. community that they need to run their code inside a game engine to get a decent experience is a hard sell. It's not a great situation compared to how easy it is on NVIDIA's stack.

[1]: https://github.com/bevyengine/bevy/blob/main/examples/shader...

This is the API you need: https://github.com/bevyengine/bevy/pull/9774