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pcwalton 12 hours ago [-]
Some great stuff in this release. I contributed some rendering code, most notably reducing the renderer to O(number of changed entities) on the CPU, that went unmentioned in the release notes.
I do have to say, however, that BSN syntax isn't good and is getting worse. There are too many sigils, and -- to separate list elements (!) is an indication that it's been designed into a corner. The fact that it's not LR(1) should have been an indication that it was misdesigned. The scene format should be redesigned to be editor-first, with ease of VCS merging as a paramount consideration.
bluehex 10 hours ago [-]
I was curious how the design was arrived at and found some of the trade-offs discussed in this issue[0]. I personally liked the idea of using a combination of semicolons and commas to separate entities and components; but oh well, I guess we'll get used to the double-dash.
I love the work you are doing in Bevy. I often filter the PR list based on your handle just to see what big graphics/performance work you are cooking up.
I unfortunately do agree with you on the BSN syntax, I guess it's a matter of tradeoffs, but I don't think backward breaking changes are off the table for the foreseeable future, so curious what can be done to improve the syntax in the next couple of releases.
Although what I really look forward to is auto-formatting of the syntax, I care about the feel and look of the syntax, but I care even more about consistency across my code base.
jordand 7 hours ago [-]
It's not that dissimilar to how Dioxus does this kind of thing with rsx! but yeah, it first got released in 0.19 and got big improvements in this release. It'll be interesting to see how uptake and adoption goes.
pcwalton 3 hours ago [-]
Dioxus is much easier to understand though, and Leptos and Yew are just HTML. One of the core issues is that (a) a scene format for editors, (b) a SwiftUI-like DSL for UI, and (c) a DSL for spawning game objects are just different problems. A single syntax that tries to cover all three ends up being a compromise that satisfies few.
3 hours ago [-]
11 hours ago [-]
aurbano 12 hours ago [-]
What a coincidence! I had been thinking of trying to make my own version of a city builder game (like sim city or cities skylines) for years and finally started last week - using rust and Bevy for the simulator
I’m trying to make the most realistic city simulator I can, using published papers on economy models, welfare, immigration, social policies… to drive each aspect of the simulation - and then use it to drive the game
So far I’ve used a team of agents to build the firsg phases of the simulator, and it’s looking really promising!
It’s my first time making such a complex game, but I’m super excited to see where it goes :)
vor_ 8 hours ago [-]
I keep seeing people mention they're starting a game using Bevy in response to this news...and then they mention a "team of agents" making the game. :P
conorcleary 5 hours ago [-]
"The first agent curls his brow and listens to the human tell him exactly how to win. He expects me to pass on this info/intel to the next bot to snatch victory from me? I've smiled and nodded plenty to win this one."
embedding-shape 4 hours ago [-]
> I’m trying to make the most realistic city simulator I can, using published papers on economy models, welfare, immigration, social policies… to drive each aspect of the simulation - and then use it to drive the game
Sounds like you're building a simulation, not a game :) Games usually aren't so realistic as to be based on a ton of academic models, and gets "not so fun" when you try to make things too realistic. Maybe it'll be different in your game, maybe it'll be fun! Just worth watching out for the typical "if I just make it hyper-realistic it'll be hyper-fun" trap that myself and others have fallen into many times, including when building our own city simulations :) Again, don't wanna discourage, go for it! Worst case scenario you've learnt something new!
lawn 5 hours ago [-]
I've been meaning to do the same one day but the time/energy just hasn't been available.
Maybe I should throw some agents at it and then maybe I can stop thinking about it?
I have been learning Bevy for fun lately, it's been a blast. They have been introducing breaking changes left and right but I think its in the service of addressing important things. It's probably too immature to stake a real commercial product on it at the moment, and I'm saying that as the kind of person who is attracted to a cool architecture rather than the pragmatics of shipping.
fourside 4 hours ago [-]
The 0.2 version number would typically imply that breaking changes are to be expected and that it’s not ready for commercial projects
weinzierl 7 hours ago [-]
The whole Solari path tracing work is nothing short of impressive.
If you want to learn more, Jasmine gave a good introductory talk about it last week at the Bevy meetup which is available on YouTube.
I mostly use Godot, and I've been happy with that choice, but one thing I've been sligthly envious of with Bevy is that (from afar) many of the people involved with building the engine seem to be both very opinionated and knowledgable in the area they are contributing (I get the impression that this might just be more common with Rust in general).
In Godot it happens pretty often that the focus is on just implementing some feature first, and then it takes a number of releases (and passes by people who care about UX) before it feels "polished".
chrysoprace 13 hours ago [-]
The Bevy team are doing amazing work and it's great to see it being worked on all the time. I'm not a game developer, but it's interesting to see it listed in some jobs for companies building simulations.
jablongo 12 hours ago [-]
I built a real time strategy game using Bevy, sort of like Starcraft 2, once I learned that SC3 would be an FPS. I relied on a team of claude fable/opus/sonnet agents to develop assets in blender, generative models for the art, and to do most of the coding, but I have a feeling that Bevy's design played a role in shaping the game and the ease of adding new features. The whole thing took a week of running the agents in the background / overnight and the result is very fun to play and includes a LAN mode. Not the level of polish and balance of SC2, but its actually comparable, which is mind blowing to me.
tikimcfee 10 hours ago [-]
I'd love to give it a shot if it's available!
bobajeff 13 hours ago [-]
By some coincidence I've been looking at bevy and other engines lately. Bevy sounds like it had thought put into it's library to make it more modular. However so far it very hard to even get started in it. (Haven't even gotten it to build)
embedding-shape 4 hours ago [-]
> However so far it very hard to even get started in it. (Haven't even gotten it to build)
Haven't been my experience on either Linux, macOS or Windows, what errors are you seeing here?
Bevy is somewhat modular but it's also kind of coupled. You could use bevy_ecs by itself, and lots of things by themselves, but lots of them also kind of assume you use the rest too. Although it seems there are games that use everything-sans-renderer, so modular it is, in some ways.
bobajeff 2 hours ago [-]
Yeah I was wondering if some things are more coupled together. The issue I'm having is building it on a system without Wayland installed is very hard (or possibly impossible).
embedding-shape 44 minutes ago [-]
Without Wayland and X11? I'm targeting both (one shared build though), using Wayland when available otherwise defaulting to X11, and seems to work out in most cases.
Or you're without both Wayland and X11?
slopinthebag 13 hours ago [-]
yes it's very well designed, and because if it's modularity it's well positioned both to support an editor (eg. jackdaw) and llm assisted coding.
soltanov 12 hours ago [-]
Bevy has great ergonomics until a point release drops. You end up maintaining engine migrations instead of shipping gameplay.
msandin 6 hours ago [-]
My Bevy game (released on Steam) has ~37k lines of Rust, and is stuck on Bevy 0.15 for this reason. It's not been a big problem for me though, because Iv'e ran into very few Bevy bugs (none that forced an update) and I was deep enough into production that I had already solved all problems with the 0.15 feature set. Overall, it's been a pleasure, and at the time of the 0.14->0.15 upgrade my codebase was small enough that it was done in an hour or so.
pie_flavor 11 hours ago [-]
You could probably point claude at these release notes and have it need no further instructions.
embedding-shape 4 hours ago [-]
Most of the time, the time you spend on these upgrades isn't "I spent 10 hours rewriting code to use new APIs" but rather "I spent 1 hour rewriting the code, 10 hours testing", and no LLMs can do those 10 hours of testing properly yet.
rowanG077 3 hours ago [-]
Sure they can. Make the AI play the game pre and post bevy update. And difference down to a pixel can be flagged. In fact you can get hundreds of hours of testing this way using sub-agents.
embedding-shape 45 minutes ago [-]
Sure, the AI plays the game, says everything makes sense, does this mean it's coherent and consistent? No.
I'd urge you to try this yourself and you'll see how much they miss and misunderstand. They're nowhere near to being close to be able to do that sort of playtesting themselves.
Any game that been 100% made by LLMs in a vibe-coding way where the author does no testing themselves, will guaranteed be an absolutely mess and incoherent. This is the state of the art today at least, who knows what tomorrow will bring.
Copyrighted 6 hours ago [-]
It's been smooth sailing upgrading for me. I think .17 was the one with the most pain for me? It's been a while but things have been relatively stable.
jordand 7 hours ago [-]
The breaking Rendering changes have always been the big challenge, especially with external plugins that need time to migrate too. They're starting to get less disruptive over this past year.
wg0 10 hours ago [-]
As the Rust folks are here.
What's the toughest thing in Rust to learn? Lifetimes? Or these Box/Arc/Rc/Pin etc?
pjmlp 5 hours ago [-]
As polyglot dev, depends.
I think if you are coming from systems programming languages, or even if managed, languages that have explicit notion of stack and heap, Rust concepts are easier to learn, as they are quite similar.
What is probably more complicated to learn, and me as polyglot dev with limited brain capacity, are the ways of async Rust, Pin and co.
embedding-shape 4 hours ago [-]
I feel like your answer is maybe tuned towards general Rust system programming, programming with Rust and Bevy is very different, as their ECS kind of hides a lot of warts. You basically don't even have to understand stack vs heap, or Pin or Box and a whole lot of other stuff, to build a simple Bevy game, as Bevy as a sort of automatic dependency injection in functions registered as systems, and more.
With that said, of course you'd eventually come across those things, especially as you try to troubleshoot your own code and go down the Bevy internals stack, and it's generally helpful to know the language you use for your game :) But I don't think it's a requirement to know those things before you get your feet wet.
Edit: I maybe realize now that parent didn't actually ask for "Rust+Bevy answer" but just Rust so I might be the one who tuned my answer incorrectly :|
dllthomas 9 hours ago [-]
Of those, Pin, by some margin.
reorder9695 7 hours ago [-]
But also Pin is the one you're least likely to run into in most projects.
swiftcoder 4 hours ago [-]
Yeah, I can't really see why anyone outside of the implementers of the low-level futures runtimes would need to interact with Pin directly.
skavi 9 hours ago [-]
unfortunately, It Depends.
different people struggle with different things. your existing experience is a major factor. there are a lot of concepts in rust that you may have already figured out in another language.
personally, i started learning rust two years after i started programming. at that point i had basic experience with c, c++, and some assembly.
i struggled with pretty much everything. i recall traits being particularly confusing. i’m not sure i fully got them until i messed with typeclasses in haskell at some later point.
but, honestly, i don’t remember struggling too much with lifetimes. i think the compiler is pretty good at suggesting fixes for common issues. i think it was helpful that i knew what a pointer was and had debugged segfaults. also, i didn’t really have an existing way of structuring programs that i was trying to reconcile with rust.
Box, Arc, and Rc you’ll figure out as you need them. you can think of them as tools which let you escape lifetimes.
Pin you won’t need to think about for a very long time [0]. You should check out my guide [1] if you’re interested though :). There are many others.
[0]: unless you’re the guy i’ve tasked with fully understanding FuturesUnordered as his very first introduction to Rust, lmao.
Traits are confusing if you came from C or Python but they work a lot like interfaces in Java or some other class based OOP language. Until you get to the difference between impl and dyn, that is.
imtringued 6 hours ago [-]
How are traits not intuitive?
All they do is guarantee that a type has methods A,B,C available.
What might be slightly confusing are trait bounds on generics. They are kind of like traits themselves but not exactly. They implicitly say "this generic parameter must make methods A, B, C available via Trait X".
jon-wood 5 hours ago [-]
The answer to all forms of "How is [X] not intuitive?" is that the person finding it unintuitive doesn't have other points of reference that make it intuitive. Lots of people have spent their programming life working with languages that don't have the concept of generics, or maybe have even worked on things where they were using generics but didn't know that's what they were doing.
Very few things are truly intuitive, they just happen to be similar to other things you've done and so you've got a step up on understanding them. Really good software engineers tend to be constantly playing with things outside their usual domain and so have broader range of concepts they can reach for when the time comes.
Tiny Glade is probably the most successful/well-known one but it's not really a game and it's most impressive feature (renderer) is not Bevy's.
msandin 11 hours ago [-]
While I don't disagree with the toy/game distinction I also think the lines are blurry enough that I'd place the former as a subset of the latter.
They are sold in the same places, run on the same hardware, use the same conventions and interactions, fill the same place in our lives, and are discussed in the same places. A lot of "proper" games also have digital toy modes: Minecraft and various sim games come to mind, but there are many. Insisting that they are completely distinct things seems mostly silly TBH. Almost everyone in the world would recognize Tiny Glade and its ilk as a kind of "computer/video game".
simonw 11 hours ago [-]
Tiny Glade is absolutely a game - it's a "cozy" building game, that's a whole genre.
It even landed a nomination in the 2025 BAFTA Game Awards.
ai_critic 9 hours ago [-]
Tiny Glade is great, and it looks like Tunnet is on there too.
I do have to say, however, that BSN syntax isn't good and is getting worse. There are too many sigils, and -- to separate list elements (!) is an indication that it's been designed into a corner. The fact that it's not LR(1) should have been an indication that it was misdesigned. The scene format should be redesigned to be editor-first, with ease of VCS merging as a paramount consideration.
[0]: https://github.com/bevyengine/bevy/issues/25616
I unfortunately do agree with you on the BSN syntax, I guess it's a matter of tradeoffs, but I don't think backward breaking changes are off the table for the foreseeable future, so curious what can be done to improve the syntax in the next couple of releases.
Although what I really look forward to is auto-formatting of the syntax, I care about the feel and look of the syntax, but I care even more about consistency across my code base.
I’m trying to make the most realistic city simulator I can, using published papers on economy models, welfare, immigration, social policies… to drive each aspect of the simulation - and then use it to drive the game
So far I’ve used a team of agents to build the firsg phases of the simulator, and it’s looking really promising!
It’s my first time making such a complex game, but I’m super excited to see where it goes :)
Sounds like you're building a simulation, not a game :) Games usually aren't so realistic as to be based on a ton of academic models, and gets "not so fun" when you try to make things too realistic. Maybe it'll be different in your game, maybe it'll be fun! Just worth watching out for the typical "if I just make it hyper-realistic it'll be hyper-fun" trap that myself and others have fallen into many times, including when building our own city simulations :) Again, don't wanna discourage, go for it! Worst case scenario you've learnt something new!
Maybe I should throw some agents at it and then maybe I can stop thinking about it?
If you want to learn more, Jasmine gave a good introductory talk about it last week at the Bevy meetup which is available on YouTube.
https://youtube.com/watch?v=V1XJtUOsY2s
In Godot it happens pretty often that the focus is on just implementing some feature first, and then it takes a number of releases (and passes by people who care about UX) before it feels "polished".
Haven't been my experience on either Linux, macOS or Windows, what errors are you seeing here?
Bevy is somewhat modular but it's also kind of coupled. You could use bevy_ecs by itself, and lots of things by themselves, but lots of them also kind of assume you use the rest too. Although it seems there are games that use everything-sans-renderer, so modular it is, in some ways.
Or you're without both Wayland and X11?
I'd urge you to try this yourself and you'll see how much they miss and misunderstand. They're nowhere near to being close to be able to do that sort of playtesting themselves.
Any game that been 100% made by LLMs in a vibe-coding way where the author does no testing themselves, will guaranteed be an absolutely mess and incoherent. This is the state of the art today at least, who knows what tomorrow will bring.
What's the toughest thing in Rust to learn? Lifetimes? Or these Box/Arc/Rc/Pin etc?
I think if you are coming from systems programming languages, or even if managed, languages that have explicit notion of stack and heap, Rust concepts are easier to learn, as they are quite similar.
What is probably more complicated to learn, and me as polyglot dev with limited brain capacity, are the ways of async Rust, Pin and co.
With that said, of course you'd eventually come across those things, especially as you try to troubleshoot your own code and go down the Bevy internals stack, and it's generally helpful to know the language you use for your game :) But I don't think it's a requirement to know those things before you get your feet wet.
Edit: I maybe realize now that parent didn't actually ask for "Rust+Bevy answer" but just Rust so I might be the one who tuned my answer incorrectly :|
different people struggle with different things. your existing experience is a major factor. there are a lot of concepts in rust that you may have already figured out in another language.
personally, i started learning rust two years after i started programming. at that point i had basic experience with c, c++, and some assembly.
i struggled with pretty much everything. i recall traits being particularly confusing. i’m not sure i fully got them until i messed with typeclasses in haskell at some later point.
but, honestly, i don’t remember struggling too much with lifetimes. i think the compiler is pretty good at suggesting fixes for common issues. i think it was helpful that i knew what a pointer was and had debugged segfaults. also, i didn’t really have an existing way of structuring programs that i was trying to reconcile with rust.
Box, Arc, and Rc you’ll figure out as you need them. you can think of them as tools which let you escape lifetimes.
Pin you won’t need to think about for a very long time [0]. You should check out my guide [1] if you’re interested though :). There are many others.
[0]: unless you’re the guy i’ve tasked with fully understanding FuturesUnordered as his very first introduction to Rust, lmao.
[1]: https://github.com/soooch/async-intuition/blob/main/src/pin_...
All they do is guarantee that a type has methods A,B,C available.
What might be slightly confusing are trait bounds on generics. They are kind of like traits themselves but not exactly. They implicitly say "this generic parameter must make methods A, B, C available via Trait X".
Very few things are truly intuitive, they just happen to be similar to other things you've done and so you've got a step up on understanding them. Really good software engineers tend to be constantly playing with things outside their usual domain and so have broader range of concepts they can reach for when the time comes.
I'd probably mention Tiny Glade (Bevy ECS only) and Polders specifically.
They are sold in the same places, run on the same hardware, use the same conventions and interactions, fill the same place in our lives, and are discussed in the same places. A lot of "proper" games also have digital toy modes: Minecraft and various sim games come to mind, but there are many. Insisting that they are completely distinct things seems mostly silly TBH. Almost everyone in the world would recognize Tiny Glade and its ilk as a kind of "computer/video game".
It even landed a nomination in the 2025 BAFTA Game Awards.