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Marco Buono 4465f256eb
Add MAY_DISCARD shader def, enabling early depth tests for most cases (#6697)
# Objective

- Right now we can't really benefit from [early depth
testing](https://www.khronos.org/opengl/wiki/Early_Fragment_Test) in our
PBR shader because it includes codepaths with `discard`, even for
situations where they are not necessary.

## Solution

- This PR introduces a new `MeshPipelineKey` and shader def,
`MAY_DISCARD`;
- All possible material/mesh options that that may result in `discard`s
being needed must set `MAY_DISCARD` ahead of time:
- Right now, this is only `AlphaMode::Mask(f32)`, but in the future
might include other options/effects; (e.g. one effect I'm personally
interested in is bayer dither pseudo-transparency for LOD transitions of
opaque meshes)
- Shader codepaths that can `discard` are guarded by an `#ifdef
MAY_DISCARD` preprocessor directive:
  - Right now, this is just one branch in `alpha_discard()`;
- If `MAY_DISCARD` is _not_ set, the `@early_depth_test` attribute is
added to the PBR fragment shader. This is a not yet documented, possibly
non-standard WGSL extension I found browsing Naga's source code. [I
opened a PR to document it
there](https://github.com/gfx-rs/naga/pull/2132). My understanding is
that for backends where this attribute is supported, it will force an
explicit opt-in to early depth test. (e.g. via
`layout(early_fragment_tests) in;` in GLSL)

## Caveats

- I included `@early_depth_test` for the sake of us being explicit, and
avoiding the need for the driver to be “smart” about enabling this
feature. That way, if we make a mistake and include a `discard`
unguarded by `MAY_DISCARD`, it will either produce errors or noticeable
visual artifacts so that we'll catch early, instead of causing a
performance regression.
- I'm not sure explicit early depth test is supported on the naga Metal
backend, which is what I'm currently using, so I can't really test the
explicit early depth test enable, I would like others with Vulkan/GL
hardware to test it if possible;
- I would like some guidance on how to measure/verify the performance
benefits of this;
- If I understand it correctly, this, or _something like this_ is needed
to fully reap the performance gains enabled by #6284;
- This will _most definitely_ conflict with #6284 and #6644. I can fix
the conflicts as needed, depending on whether/the order they end up
being merging in.

---

## Changelog

### Changed

- Early depth tests are now enabled whenever possible for meshes using
`StandardMaterial`, reducing the number of fragments evaluated for
scenes with lots of occlusions.
2023-05-29 15:15:01 +00:00
.cargo Change recommended linker: zld to lld for MacOS (#7496) 2023-02-06 18:24:12 +00:00
.github Webgpu support (#8336) 2023-05-04 22:07:57 +00:00
assets Fix screenspace_texture example shader compiler error in WebGPU (Browser) (#8682) 2023-05-25 21:54:29 +00:00
benches update syn, encase, glam and hexasphere (#8573) 2023-05-16 01:24:17 +00:00
crates Add MAY_DISCARD shader def, enabling early depth tests for most cases (#6697) 2023-05-29 15:15:01 +00:00
docs Add support for pnm textures (#8601) 2023-05-16 23:51:47 +00:00
docs-template audio and browsers section for wasm examples (#8625) 2023-05-17 23:54:35 +00:00
errors Schedule-First: the new and improved add_systems (#8079) 2023-03-18 01:45:34 +00:00
examples fix new clippy lints before they reach stable (#8700) 2023-05-29 07:23:50 +00:00
src Schedule-First: the new and improved add_systems (#8079) 2023-03-18 01:45:34 +00:00
tests Schedule-First: the new and improved add_systems (#8079) 2023-03-18 01:45:34 +00:00
tools Optimize wasm examples for the website (#8636) 2023-05-19 17:57:54 +00:00
.gitattributes Enforce linux-style line endings for .rs and .toml (#3197) 2021-11-26 21:05:35 +00:00
.gitignore Wgpu 0.15 (#7356) 2023-01-29 20:27:30 +00:00
Cargo.toml Disable asset_loading and texture_atlas examples when building for wasm / WebGPU (#8683) 2023-05-25 21:57:04 +00:00
CHANGELOG.md Add 0.10.0 changelog (#7926) 2023-03-06 10:23:22 +00:00
clippy.toml Enable the doc_markdown clippy lint (#3457) 2022-01-09 23:20:13 +00:00
CODE_OF_CONDUCT.md Update CODE_OF_CONDUCT.md 2020-08-19 20:25:58 +01:00
CONTRIBUTING.md Add examples page build instructions (#8413) 2023-04-17 16:13:24 +00:00
CREDITS.md Add support for custom glTF vertex attributes. (#5370) 2023-04-24 14:20:13 +00:00
deny.toml Basic spatial audio (#6028) 2023-02-20 15:31:07 +00:00
LICENSE-APACHE Let the project page support GitHub's new ability to display open source licenses (#4966) 2022-06-08 17:55:57 +00:00
LICENSE-MIT Let the project page support GitHub's new ability to display open source licenses (#4966) 2022-06-08 17:55:57 +00:00
README.md Update MSRV desc in README.md (#8546) 2023-05-09 13:52:53 +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 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

  • The Bevy Book: Bevy's official documentation. 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.

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 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

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.

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

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, Fyrox, 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.

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:

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.