Máté Homolya
18596dc888
# Objective **Anecdotal feedback:** - no floating origin support for implementing large-scale worlds, forked Bevy's atmosphere at https://github.com/philpax/veldera/blob/main/crates/bevy_pbr_atmosphere_planet/NOTICE.md - no custom up axis support, resorted to using a custom sky shader for flight simulator with Z up coordinate system. Bevy's atmosphere appears tilted at a 90 degree angle with no way of changing it. ## Solution - Atmosphere component can be spawned stand-alone - AtmosphereSettings remains on camera - A closest-to-camera heuristic is used to pick the primary atmosphere to render. Deliberately no multi-atmosphere support to keep the scope of this PR small and self contained. See https://github.com/mate-h/bevy/pull/19 at an attempt. - `scene_units_to_m` removed in favor of using `Transform` - Z up now possible by offsetting the viewer position to the equator - Floating origin systems now possible - Simplify the `AtmosphereBuffer` / `AtmosphereData` structs to just use the plain extracted `GpuAtmosphere` struct. this reduces the complexity of the struct in the mesh view bindings. Since atmosphere settings is coupled with the rendering pipeline of the atmosphere this makes sense architecturally. - We no longer hard code the offset to the north pole from the planet center in places. **Why not multi atmosphere:** The atmosphere uses multiple LUTs (lookup textures) to accelerate the rendering performance. Some of them are not view dependent: - Transmittance LUT - Multiple scattering LUT - Scattering / density LUTs These can be coupled and rendered for each atmosphere individually. However the remainder of the pipeline is view dependent: - Aerial View LUT - Sky View LUT - Render Sky pass In raymarched rendering mode, these LUTs can be skipped and only the render sky pass runs sampling on all of the atmospheres with a raymarch in screen space. Further, the Sky View LUT uses a local reference frame to concentrate texel density along the horizon's local up axis. This in turn means it's coupled with both a _specific_ atmosphere's local coordinates as well as the view's transform matrix. We cannot consider rendering both atmospheres into a single LUT for this reason. So it has to be unique for each pair of (view, atmosphere). Given two views and two atmospheres we would need 4 of these Sky View LUTs and at some point, raymarched rendering will become the less expensive option. Lastly the Render Sky pass needs to happen once per view, we cannot realistically composite them in sequence with simple dual-source blending as we do with the scene, this would result in incorrect scattering integration. This in turn means we need to bind ALL of the luts calculated previously so a single render sky pass and render aerial view lut - perhaps making use of array textures. Rely on unified volumetric ingegration in the raymarching loop: for each light,for each atmosphere, attenuate inscattering and transmittance along the path integral. It is suffice to say this change is overall _too complex_ for the time being and is likely the reason Unreal Engine also do not support multiple atmospheres. For context: our research is based heavily on Sebastian Hillarie's work, one of the Unreal graphics engineers. That being said about multiple atmospheres - I am thinking of this PR as a segway into unified volumetrics in Bevy. that is: Render the FogVolume and Atmosphere in a single pass! Making use of the frustum aligned voxel grid "froxel" approach to accelerate the rendering. This would drastically increase the performance for scenes wanting to make use of both the atmosphere and local fog volumes. ## Testing - Ran the `examples/3d/atmosphere.rs` example. --- ## Showcase (example screenshot unchanged compared to main.) ```rs // Spawn earth atmosphere commands.spawn(Atmosphere::earth(earth_medium)); commands.spawn(( Camera3d::default(), // Can be adjusted to change the rendering quality AtmosphereSettings::default(), )); ``` --------- Co-authored-by: Emerson Coskey <emerson@coskey.dev>
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.
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.