5adf831b42
This patch adds the infrastructure necessary for Bevy to support *bindless resources*, by adding a new `#[bindless]` attribute to `AsBindGroup`. Classically, only a single texture (or sampler, or buffer) can be attached to each shader binding. This means that switching materials requires breaking a batch and issuing a new drawcall, even if the mesh is otherwise identical. This adds significant overhead not only in the driver but also in `wgpu`, as switching bind groups increases the amount of validation work that `wgpu` must do. *Bindless resources* are the typical solution to this problem. Instead of switching bindings between each texture, the renderer instead supplies a large *array* of all textures in the scene up front, and the material contains an index into that array. This pattern is repeated for buffers and samplers as well. The renderer now no longer needs to switch binding descriptor sets while drawing the scene. Unfortunately, as things currently stand, this approach won't quite work for Bevy. Two aspects of `wgpu` conspire to make this ideal approach unacceptably slow: 1. In the DX12 backend, all binding arrays (bindless resources) must have a constant size declared in the shader, and all textures in an array must be bound to actual textures. Changing the size requires a recompile. 2. Changing even one texture incurs revalidation of all textures, a process that takes time that's linear in the total size of the binding array. This means that declaring a large array of textures big enough to encompass the entire scene is presently unacceptably slow. For example, if you declare 4096 textures, then `wgpu` will have to revalidate all 4096 textures if even a single one changes. This process can take multiple frames. To work around this problem, this PR groups bindless resources into small *slabs* and maintains a free list for each. The size of each slab for the bindless arrays associated with a material is specified via the `#[bindless(N)]` attribute. For instance, consider the following declaration: ```rust #[derive(AsBindGroup)] #[bindless(16)] struct MyMaterial { #[buffer(0)] color: Vec4, #[texture(1)] #[sampler(2)] diffuse: Handle<Image>, } ``` The `#[bindless(N)]` attribute specifies that, if bindless arrays are supported on the current platform, each resource becomes a binding array of N instances of that resource. So, for `MyMaterial` above, the `color` attribute is exposed to the shader as `binding_array<vec4<f32>, 16>`, the `diffuse` texture is exposed to the shader as `binding_array<texture_2d<f32>, 16>`, and the `diffuse` sampler is exposed to the shader as `binding_array<sampler, 16>`. Inside the material's vertex and fragment shaders, the applicable index is available via the `material_bind_group_slot` field of the `Mesh` structure. So, for instance, you can access the current color like so: ```wgsl // `uniform` binding arrays are a non-sequitur, so `uniform` is automatically promoted // to `storage` in bindless mode. @group(2) @binding(0) var<storage> material_color: binding_array<Color, 4>; ... @fragment fn fragment(in: VertexOutput) -> @location(0) vec4<f32> { let color = material_color[mesh[in.instance_index].material_bind_group_slot]; ... } ``` Note that portable shader code can't guarantee that the current platform supports bindless textures. Indeed, bindless mode is only available in Vulkan and DX12. The `BINDLESS` shader definition is available for your use to determine whether you're on a bindless platform or not. Thus a portable version of the shader above would look like: ```wgsl #ifdef BINDLESS @group(2) @binding(0) var<storage> material_color: binding_array<Color, 4>; #else // BINDLESS @group(2) @binding(0) var<uniform> material_color: Color; #endif // BINDLESS ... @fragment fn fragment(in: VertexOutput) -> @location(0) vec4<f32> { #ifdef BINDLESS let color = material_color[mesh[in.instance_index].material_bind_group_slot]; #else // BINDLESS let color = material_color; #endif // BINDLESS ... } ``` Importantly, this PR *doesn't* update `StandardMaterial` to be bindless. So, for example, `scene_viewer` will currently not run any faster. I intend to update `StandardMaterial` to use bindless mode in a follow-up patch. A new example, `shaders/shader_material_bindless`, has been added to demonstrate how to use this new feature. Here's a Tracy profile of `submit_graph_commands` of this patch and an additional patch (not submitted yet) that makes `StandardMaterial` use bindless. Red is those patches; yellow is `main`. The scene was Bistro Exterior with a hack that forces all textures to opaque. You can see a 1.47x mean speedup. ![Screenshot 2024-11-12 161713](https://github.com/user-attachments/assets/4334b362-42c8-4d64-9cfb-6835f019b95c) ## Migration Guide * `RenderAssets::prepare_asset` now takes an `AssetId` parameter. * Bin keys now have Bevy-specific material bind group indices instead of `wgpu` material bind group IDs, as part of the bindless change. Use the new `MaterialBindGroupAllocator` to map from bind group index to bind group ID. |
||
---|---|---|
.cargo | ||
.github | ||
assets | ||
benches | ||
crates | ||
docs | ||
docs-template | ||
errors | ||
examples | ||
src | ||
tests | ||
tools | ||
.gitattributes | ||
.gitignore | ||
Cargo.toml | ||
clippy.toml | ||
CODE_OF_CONDUCT.md | ||
CONTRIBUTING.md | ||
CREDITS.md | ||
deny.toml | ||
LICENSE-APACHE | ||
LICENSE-MIT | ||
README.md | ||
rustfmt.toml | ||
typos.toml |
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.