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# Objective #16132 introduced entity cloning functionality, and while it works and is useful, it can be made faster. This is the promised follow-up to improve performance. ## Solution **PREFACE**: This is my first time writing `unsafe` in rust and I have only vague idea about what I'm doing. I would encourage reviewers to scrutinize `unsafe` parts in particular. The solution is to clone component data to an intermediate buffer and use `EntityWorldMut::insert_by_ids` to insert components without additional archetype moves. To facilitate this, `EntityCloner::clone_entity` now reads all components of the source entity and provides clone handlers with the ability to read component data straight from component storage using `read_source_component` and write to an intermediate buffer using `write_target_component`. `ComponentId` is used to check that requested type corresponds to the type available on source entity. Reflect-based handler is a little trickier to pull of: we only have `&dyn Reflect` and no direct access to the underlying data. `ReflectFromPtr` can be used to get `&dyn Reflect` from concrete component data, but to write it we need to create a clone of the underlying data using `Reflect`. For this reason only components that have `ReflectDefault` or `ReflectFromReflect` or `ReflectFromWorld` can be cloned, all other components will be skipped. The good news is that this is actually only a temporary limitation: once #13432 lands we will be able to clone component without requiring one of these `type data`s. This PR also introduces `entity_cloning` benchmark to better compare changes between the PR and main, you can see the results in the **showcase** section. ## Testing - All previous tests passing - Added test for fast reflect clone path (temporary, will be removed after reflection-based cloning lands) - Ran miri ## Showcase Here's a table demonstrating the improvement: | **benchmark** | **main, avg** | **PR, avg** | **change, avg** | | ----------------------- | ------------- | ----------- | --------------- | | many components reflect | 18.505 µs | 2.1351 µs | -89.095% | | hierarchy wide reflect* | 22.778 ms | 4.1875 ms | -81.616% | | hierarchy tall reflect* | 107.24 µs | 26.322 µs | -77.141% | | hierarchy many reflect | 78.533 ms | 9.7415 ms | -87.596% | | many components clone | 1.3633 µs | 758.17 ns | -45.937% | | hierarchy wide clone* | 2.7716 ms | 3.3411 ms | +20.546% | | hierarchy tall clone* | 17.646 µs | 20.190 µs | +17.379% | | hierarchy many clone | 5.8779 ms | 4.2650 ms | -27.439% | *: these benchmarks have entities with only 1 component ## Considerations Once #10154 is resolved a large part of the functionality in this PR will probably become obsolete. It might still be a little bit faster than using command batching, but the complexity might not be worth it. ## Migration Guide - `&EntityCloner` in component clone handlers is changed to `&mut ComponentCloneCtx` to better separate data. - Changed `EntityCloneHandler` from enum to struct and added convenience functions to add default clone and reflect handler more easily. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com> |
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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 early stages of development. Important features are missing. Documentation is sparse. A new version of Bevy containing breaking changes to the API is released approximately once every 3 months. We provide migration guides, but we can't guarantee migrations will always be easy. Use only if you are willing to work in this environment.
MSRV: Bevy relies heavily on improvements in the Rust language and compiler. As a result, the Minimum Supported Rust Version (MSRV) is generally close to "the latest stable release" of Rust.
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
- Features: A quick overview of Bevy's features.
- News: A development blog that covers our progress, plans and shiny new features.
Docs
- Quick Start Guide: Bevy's official Quick Start Guide. The best place to start learning Bevy.
- Bevy Rust API Docs: Bevy's Rust API docs, which are automatically generated from the doc comments in this repo.
- Official Examples: Bevy's dedicated, runnable examples, which are great for digging into specific concepts.
- Community-Made Learning Resources: More tutorials, documentation, and examples made by the Bevy community.
Community
Before contributing or participating in discussions with the community, you should familiarize yourself with our Code of Conduct.
- Discord: Bevy's official discord server.
- Reddit: Bevy's official subreddit.
- GitHub Discussions: The best place for questions about Bevy, answered right here!
- Bevy Assets: A collection of awesome Bevy projects, tools, plugins and learning materials.
Contributing
If you'd like to help build Bevy, check out the Contributor's Guide. For simple problems, feel free to open an issue or PR and tackle it yourself!
For more complex architecture decisions and experimental mad science, please open an RFC (Request For Comments) so we can brainstorm together effectively!
Getting Started
We recommend checking out the Quick Start Guide for a brief introduction.
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
To draw a window with standard functionality enabled, use:
use bevy::prelude::*;
fn main(){
App::new()
.add_plugins(DefaultPlugins)
.run();
}
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.
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.
Thanks
Bevy is the result of the hard work of many people. A huge thanks to all Bevy contributors, the many open source projects that have come before us, the Rust gamedev ecosystem, and the many libraries we build on.
A huge thanks to Bevy's generous sponsors. Bevy will always be free and open source, but it isn't free to make. Please consider sponsoring our work if you like what we're building.
This project is tested with BrowserStack.
License
Bevy is free, open source and permissively licensed! Except where noted (below and/or in individual files), all code in this repository is dual-licensed under either:
- MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
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.
Some of the engine's code carries additional copyright notices and license terms due to their external origins.
These are generally BSD-like, but exact details vary by crate:
If the README of a crate contains a 'License' header (or similar), the additional copyright notices and license terms applicable to that crate will be listed.
The above licensing requirement still applies to contributions to those crates, and sections of those crates will carry those license terms.
The license field of each crate will also reflect this.
For example, bevy_mikktspace has code under the Zlib license (as well as a copyright notice when choosing the MIT license).
The assets included in this repository (for our examples) typically fall under different open licenses. These will not be included in your game (unless copied in by you), and they are not distributed in the published bevy crates. See CREDITS.md for the details of the licenses of those files.
Your contributions
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.