No description
Find a file
Carter Anderson 9d453530fa System Param Lifetime Split (#2605)
# Objective

Enable using exact World lifetimes during read-only access . This is motivated by the new renderer's need to allow read-only world-only queries to outlive the query itself (but still be constrained by the world lifetime).

For example:
115b170d1f/pipelined/bevy_pbr2/src/render/mod.rs (L774)

## Solution

Split out SystemParam state and world lifetimes and pipe those lifetimes up to read-only Query ops (and add into_inner for Res). According to every safety test I've run so far (except one), this is safe (see the temporary safety test commit). Note that changing the mutable variants to the new lifetimes would allow aliased mutable pointers (try doing that to see how it affects the temporary safety tests).

The new state lifetime on SystemParam does make `#[derive(SystemParam)]` more cumbersome (the current impl requires PhantomData if you don't use both lifetimes). We can make this better by detecting whether or not a lifetime is used in the derive and adjusting accordingly, but that should probably be done in its own pr.  

## Why is this a draft?

The new lifetimes break QuerySet safety in one very specific case (see the query_set system in system_safety_test). We need to solve this before we can use the lifetimes given.

This is due to the fact that QuerySet is just a wrapper over Query, which now relies on world lifetimes instead of `&self` lifetimes to prevent aliasing (but in systems, each Query has its own implied lifetime, not a centralized world lifetime).  I believe the fix is to rewrite QuerySet to have its own World lifetime (and own the internal reference). This will complicate the impl a bit, but I think it is doable. I'm curious if anyone else has better ideas.

Personally, I think these new lifetimes need to happen. We've gotta have a way to directly tie read-only World queries to the World lifetime. The new renderer is the first place this has come up, but I doubt it will be the last. Worst case scenario we can come up with a second `WorldLifetimeQuery<Q, F = ()>` parameter to enable these read-only scenarios, but I'd rather not add another type to the type zoo.
2021-08-15 20:51:53 +00:00
.cargo Removed irrelevant note for Mac users (#2017) 2021-04-27 00:46:41 +00:00
.github Comprehensive CONTRIBUTING.md (#2040) 2021-08-14 19:21:36 +00:00
assets Fixes #2079 with a New SVG File (#2290) 2021-06-02 02:11:04 +00:00
benches Not me ... us (#2654) 2021-08-15 20:08:52 +00:00
crates System Param Lifetime Split (#2605) 2021-08-15 20:51:53 +00:00
docs Remove bevy_dynamic_plugin as a default (#2578) 2021-08-01 19:14:47 +00:00
examples System Param Lifetime Split (#2605) 2021-08-15 20:51:53 +00:00
src Down with the system! (#2496) 2021-07-27 23:42:36 +00:00
tests Down with the system! (#2496) 2021-07-27 23:42:36 +00:00
tools Not me ... us (#2654) 2021-08-15 20:08:52 +00:00
.gitattributes Comprehensive CONTRIBUTING.md (#2040) 2021-08-14 19:21:36 +00:00
.gitignore add .cargo/config.toml to .gitignore 2020-12-12 17:17:35 -08:00
Cargo.toml Not me ... us (#2654) 2021-08-15 20:08:52 +00:00
CHANGELOG.md update CHANGELOG for 0.5 (#1967) 2021-04-19 22:41:19 +00:00
CODE_OF_CONDUCT.md Update CODE_OF_CONDUCT.md 2020-08-19 20:25:58 +01:00
CONTRIBUTING.md Not me ... us (#2654) 2021-08-15 20:08:52 +00:00
CREDITS.md Cleanup of Markdown Files and add CI Checking (#1463) 2021-02-22 04:50:05 +00:00
deny.toml add proc-macro-crate as a known duplicate (#2456) 2021-07-13 21:51:44 +00:00
LICENSE Relicense Bevy under the dual MIT or Apache-2.0 license (#2509) 2021-07-23 21:11:51 +00:00
README.md Relicense Bevy under the dual MIT or Apache-2.0 license (#2509) 2021-07-23 21:11:51 +00:00
rustfmt.toml Cargo fmt with unstable features (#1903) 2021-04-21 23:19:34 +00:00

Bevy

Crates.io MIT/Apache 2.0 Crates.io Rust iOS cron CI Discord

What is Bevy?

Bevy is a refreshingly simple data-driven game engine built in Rust. It is free and open-source forever!

WARNING

Bevy is still in the very early stages of development. APIs can and will change (now is the time to make suggestions!). Important features are missing. Documentation is sparse. Please don't build any serious projects in Bevy unless you are prepared to be broken by API changes constantly.

Design Goals

  • Capable: Offer a complete 2D and 3D feature set
  • Simple: Easy for newbies to pick up, but infinitely flexible for power users
  • Data Focused: Data-oriented architecture using the Entity Component System paradigm
  • Modular: Use only what you need. Replace what you don't like
  • Fast: App logic should run quickly, and when possible, in parallel
  • Productive: Changes should compile quickly ... waiting isn't fun

About

Docs

Community

Before contributing or participating in discussions with the community, you should familiarize yourself with our Code of Conduct and How to Contribute

Getting Started

We recommend checking out The Bevy Book for a full tutorial.

Follow the Setup guide to ensure your development environment is set up correctly. Once set up, you can quickly try out the examples by cloning this repo and running the following commands:

# Switch to the correct version (latest release, default is main development branch)
git checkout latest
# Runs the "breakout" example
cargo run --example breakout

Fast Compiles

Bevy can be built just fine using default configuration on stable Rust. However for really fast iterative compiles, you should enable the "fast compiles" setup by following the instructions here.

Focus Areas

Bevy has the following Focus Areas. We are currently focusing our development efforts in these areas, and they will receive priority for Bevy developers' time. If you would like to contribute to Bevy, you are heavily encouraged to join in on these efforts:

Editor-Ready UI

PBR / Clustered Forward Rendering

Scenes

Libraries Used

Bevy is only possible because of the hard work put into these foundational technologies:

  • wgpu: modern / low-level / cross-platform graphics library inspired by Vulkan
  • glam-rs: a simple and fast 3D math library for games and graphics
  • winit: cross-platform window creation and management in Rust
  • spirv-reflect: Reflection API in rust for SPIR-V shader byte code

Bevy Cargo Features

This list outlines the different cargo features supported by Bevy. These allow you to customize the Bevy feature set for your use-case.

Third Party Plugins

Plugins are very welcome to extend Bevy's features. Guidelines are available to help integration and usage.

Thanks and Alternatives

Additionally, we would like to thank the Amethyst, macroquad, coffee, ggez, rg3d, and Piston projects for providing solid examples of game engine development in Rust. If you are looking for a Rust game engine, it is worth considering all of your options. Each engine has different design goals, and some will likely resonate with you more than others.

License

Bevy is free and open source! All code in this repository is dual-licensed under either:

at your option. This means you can select the license you prefer! This dual-licensing approach is the de-facto standard in the Rust ecosystem and there are very good reasons to include both.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.