legion VS bevy

I know bevy, there is also legion from the amethyst game framework.

Wow... Okay. I see you didn't even bother watching the video in full. But, I'll respond in case your misinformed comment manages to deter people from watching it.

You somehow managed to ignore all the points of the talk. Like literally every one of them, and I'm not even exaggerating. And then you somehow both managed to focused on irrelevant details and to talk out of your ass (like, at least be right about the details?), all to make a tangential point about how "sUpErIoRlY sMaRt CpP dEvs ArE" because they know this really basic shit.

Let's start.

First you talk about "borrow checker issues" she's demonstrating in the OOO design. The point here was to illustrate the amount of coupling and "explosion" in size with this approach. The point was "OOO is probably not a good design paradigm for game dev". Then she continues how Rust surfaces this bad design paradigm much earlier than it would've happened in other languages/ecosystems. That's all.

More, what you call a custom allocator with tombstoning/generations are just things that exist with a lot of ECS implementations (regardless of language), and it's just become "tribal wisdom" at this point that this table-esque storage backend work really well with ECS (I dunno which one came first; older game devs might know more about ECS history/evolution than I do).

Also not sure what you mean by "that can fail in most of the typical ways and that she's gained nothing over the cpp implementation while wasting effort to force Rust into allowing her to do something really basic"... Maybe I misunderstand what you mean, but it sounds to me like you're comparing working with `Option` as being the same failure mode as working with `void`. That's just utterly ludicrous nonsense.

Her ECS implementation is... Well, it was made to fit inside a few slides for a 40-minute talk. So, yeah it's not great; there's plenty of small issues with it, but none of them are with Rust, or with ECS itself... Did you expect a production ready ECS library you can copy off of slides and use them in your next game, lol? If anything, her implementation has too much passing resemblance with what a C++ implementation would look like (which is something she's very familiar with and her starting point) than a Rust one. So, I'm just bewildered why this is the bone you decided to pick.

If you're interested in what a production-ish ECS implementation in Rust looks like, check out Amethyst's Legion or Bevy's ECS. Although, Bevy takes takes ECS a few... staircases (rather than steps) further with its own ECS. I really* encourage everyone to read up on Bevy's ECS and check out the unofficial Bevy cheatsheet book; I'm certain at leat UE game devs will know how to appreciate how beautiful and ergonomic the design is, but others should as well). Aside: her ECS implementation is still safer than most C/C++ implementations used in published games, but that's a bit besides the point since that's the borrow checker doing its job.

Anyway, the irony is that she much better explains the pitfalls of her own implementation details that you do and she also explains why they're "fine" sometimes. And it was kinda implied that it's fine (from what I remember) because it's no worse than what you end up doing in C++ or Java when implementing ECS, but at least it's safe in Rust. She acknowledges that there's probably better ways to do it.

Here's a few links on some of the stuff I mentioned:

- https://github.com/amethyst/legion

- https://bevyengine.org/learn/book/getting-started/ecs/

Development on Amethyst (the engine) stopped, the Amethyst Foundation is now focusing on developing engine agnostic tools, like Legion and Distill

Though, Legion Github was not too active during this year, and with the recent shutdown repurpose of Amethyst Foundation its future looks even less promising.

Take a look at legion on how to compose data objects in Rust.

I'm trying to avoid that architecture even though that's the path of least resistance to work with existing ECS libs in rust.This discussion about FFI for legion touches on what I'm trying to accomplish. They use a u32 as a custom type ID to deal with the FFI boundary. The size param would be for each instance of that registered component, so the Vec wouldn't have knowledge of the size of each component (which might be 16 bytes for example). Ideally, components and systems defined in the scripting language are more 'first class' instead of scripts only being invoked by entities with a DynamicComponent. This discussion is very helpful btw, I appreciate your thoughts

In the end, I got something to work (also in issue 269):

I ended up with my own, a bit ugly, code. I'll quote it here, because even deserializing a JSON into Legion components is not 100% trivial task. Someone else filed an issue 268 in Legion, I have filed another one too.

Bevy was introduced in 2020 and the patent was filed in 2018. I don't think any of the ECS mentioned predate the patent filing (looks like legion introduced this model in 2019), so it's not as derivative as it seems in the current landscape.

I have been working on a game using Rust, SDL2 and Legion. I statically link SDL2, which mean that only the parts that I actually use gets included. Also i have been using the include_bytes to include my assets. This creates a single executable that is around 3mb (this is without compiler optimizing for size, it could go lower at the cost of runtime speed). Running (upx)https://github.com/upx/upx on it, it comes out to about 900kb.

Bevy. A very young engine where you need to write the game entirely in Rust—that was appealing. But fatal flaws overshadowed everything: no editor, the engine brutally enforces the ECS approach, and the game's architecture must literally bend to fit this paradigm. So, you won't migrate to another engine at all—you just throw away all the code and start from scratch.

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