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- Adopted from #14449 - Still fixes #12144. ## Migration Guide The retained render world is a complex change: migrating might take one of a few different forms depending on the patterns you're using. For every example, we specify in which world the code is run. Most of the changes affect render world code, so for the average Bevy user who's using Bevy's high-level rendering APIs, these changes are unlikely to affect your code. ### Spawning entities in the render world Previously, if you spawned an entity with `world.spawn(...)`, `commands.spawn(...)` or some other method in the rendering world, it would be despawned at the end of each frame. In 0.15, this is no longer the case and so your old code could leak entities. This can be mitigated by either re-architecting your code to no longer continuously spawn entities (like you're used to in the main world), or by adding the `bevy_render::world_sync::TemporaryRenderEntity` component to the entity you're spawning. Entities tagged with `TemporaryRenderEntity` will be removed at the end of each frame (like before). ### Extract components with `ExtractComponentPlugin` ``` // main world app.add_plugins(ExtractComponentPlugin::<ComponentToExtract>::default()); ``` `ExtractComponentPlugin` has been changed to only work with synced entities. Entities are automatically synced if `ComponentToExtract` is added to them. However, entities are not "unsynced" if any given `ComponentToExtract` is removed, because an entity may have multiple components to extract. This would cause the other components to no longer get extracted because the entity is not synced. So be careful when only removing extracted components from entities in the render world, because it might leave an entity behind in the render world. The solution here is to avoid only removing extracted components and instead despawn the entire entity. ### Manual extraction using `Extract<Query<(Entity, ...)>>` ```rust // in render world, inspired by bevy_pbr/src/cluster/mod.rs pub fn extract_clusters( mut commands: Commands, views: Extract<Query<(Entity, &Clusters, &Camera)>>, ) { for (entity, clusters, camera) in &views { // some code commands.get_or_spawn(entity).insert(...); } } ``` One of the primary consequences of the retained rendering world is that there's no longer a one-to-one mapping from entity IDs in the main world to entity IDs in the render world. Unlike in Bevy 0.14, Entity 42 in the main world doesn't necessarily map to entity 42 in the render world. Previous code which called `get_or_spawn(main_world_entity)` in the render world (`Extract<Query<(Entity, ...)>>` returns main world entities). Instead, you should use `&RenderEntity` and `render_entity.id()` to get the correct entity in the render world. Note that this entity does need to be synced first in order to have a `RenderEntity`. When performing manual abstraction, this won't happen automatically (like with `ExtractComponentPlugin`) so add a `SyncToRenderWorld` marker component to the entities you want to extract. This results in the following code: ```rust // in render world, inspired by bevy_pbr/src/cluster/mod.rs pub fn extract_clusters( mut commands: Commands, views: Extract<Query<(&RenderEntity, &Clusters, &Camera)>>, ) { for (render_entity, clusters, camera) in &views { // some code commands.get_or_spawn(render_entity.id()).insert(...); } } // in main world, when spawning world.spawn(Clusters::default(), Camera::default(), SyncToRenderWorld) ``` ### Looking up `Entity` ids in the render world As previously stated, there's now no correspondence between main world and render world `Entity` identifiers. Querying for `Entity` in the render world will return the `Entity` id in the render world: query for `MainEntity` (and use its `id()` method) to get the corresponding entity in the main world. This is also a good way to tell the difference between synced and unsynced entities in the render world, because unsynced entities won't have a `MainEntity` component. --------- Co-authored-by: re0312 <re0312@outlook.com> Co-authored-by: re0312 <45868716+re0312@users.noreply.github.com> Co-authored-by: Periwink <charlesbour@gmail.com> Co-authored-by: Anselmo Sampietro <ans.samp@gmail.com> Co-authored-by: Emerson Coskey <56370779+ecoskey@users.noreply.github.com> Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: Christian Hughes <9044780+ItsDoot@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.