8976a45199
Currently, Bevy rebuilds the buffer containing all the transforms for joints every frame, during the extraction phase. This is inefficient in cases in which many skins are present in the scene and their joints don't move, such as the Caldera test scene. To address this problem, this commit switches skin extraction to use a set of retained GPU buffers with allocations managed by the offset allocator. I use fine-grained change detection in order to determine which skins need updating. Note that the granularity is on the level of an entire skin, not individual joints. Using the change detection at that level would yield poor performance in common cases in which an entire skin is animated at once. Also, this patch yields additional performance from the fact that changing joint transforms no longer requires the skinned mesh to be re-extracted. Note that this optimization can be a double-edged sword. In `many_foxes`, fine-grained change detection regressed the performance of `extract_skins` by 3.4x. This is because every joint is updated every frame in that example, so change detection is pointless and is pure overhead. Because the `many_foxes` workload is actually representative of animated scenes, this patch includes a heuristic that disables fine-grained change detection if the number of transformed entities in the frame exceeds a certain fraction of the total number of joints. Currently, this threshold is set to 25%. Note that this is a crude heuristic, because it doesn't distinguish between the number of transformed *joints* and the number of transformed *entities*; however, it should be good enough to yield the optimum code path most of the time. Finally, this patch fixes a bug whereby skinned meshes are actually being incorrectly retained if the buffer offsets of the joints of those skinned meshes changes from frame to frame. To fix this without retaining skins, we would have to re-extract every skinned mesh every frame. Doing this was a significant regression on Caldera. With this PR, by contrast, mesh joints stay at the same buffer offset, so we don't have to update the `MeshInputUniform` containing the buffer offset every frame. This also makes PR #17717 easier to implement, because that PR uses the buffer offset from the previous frame, and the logic for calculating that is simplified if the previous frame's buffer offset is guaranteed to be identical to that of the current frame. On Caldera, this patch reduces the time spent in `extract_skins` from 1.79 ms to near zero. On `many_foxes`, this patch regresses the performance of `extract_skins` by approximately 10%-25%, depending on the number of foxes. This has only a small impact on frame rate. |
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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.