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This PR adds support for *mixed lighting* to Bevy, whereby some parts of the scene are lightmapped, while others take part in real-time lighting. (Here *real-time lighting* means lighting at runtime via the PBR shader, as opposed to precomputed light using lightmaps.) It does so by adding a new field, `affects_lightmapped_meshes` to `IrradianceVolume` and `AmbientLight`, and a corresponding field `affects_lightmapped_mesh_diffuse` to `DirectionalLight`, `PointLight`, `SpotLight`, and `EnvironmentMapLight`. By default, this value is set to true; when set to false, the light contributes nothing to the diffuse irradiance component to meshes with lightmaps. Note that specular light is unaffected. This is because the correct way to bake specular lighting is *directional lightmaps*, which we have no support for yet. There are two general ways I expect this field to be used: 1. When diffuse indirect light is baked into lightmaps, irradiance volumes and reflection probes shouldn't contribute any diffuse light to the static geometry that has a lightmap. That's because the baking tool should have already accounted for it, and in a higher-quality fashion, as lightmaps typically offer a higher effective texture resolution than the light probe does. 2. When direct diffuse light is baked into a lightmap, punctual lights shouldn't contribute any diffuse light to static geometry with a lightmap, to avoid double-counting. It may seem odd to bake *direct* light into a lightmap, as opposed to indirect light. But there is a use case: in a scene with many lights, avoiding light leaks requires shadow mapping, which quickly becomes prohibitive when many lights are involved. Baking lightmaps allows light leaks to be eliminated on static geometry. A new example, `mixed_lighting`, has been added. It demonstrates a sofa (model from the [glTF Sample Assets]) that has been lightmapped offline using [Bakery]. It has four modes: 1. In *baked* mode, all objects are locked in place, and all the diffuse direct and indirect light has been calculated ahead of time. Note that the bottom of the sphere has a red tint from the sofa, illustrating that the baking tool captured indirect light for it. 2. In *mixed direct* mode, lightmaps capturing diffuse direct and indirect light have been pre-calculated for the static objects, but the dynamic sphere has real-time lighting. Note that, because the diffuse lighting has been entirely pre-calculated for the scenery, the dynamic sphere casts no shadow. In a real app, you would typically use real-time lighting for the most important light so that dynamic objects can shadow the scenery and relegate baked lighting to the less important lights for which shadows aren't as important. Also note that there is no red tint on the sphere, because there is no global illumination applied to it. In an actual game, you could fix this problem by supplementing the lightmapped objects with an irradiance volume. 3. In *mixed indirect* mode, all direct light is calculated in real-time, and the static objects have pre-calculated indirect lighting. This corresponds to the mode that most applications are expected to use. Because direct light on the scenery is computed dynamically, shadows are fully supported. As in mixed direct mode, there is no global illumination on the sphere; in a real application, irradiance volumes could be used to supplement the lightmaps. 4. In *real-time* mode, no lightmaps are used at all, and all punctual lights are rendered in real-time. No global illumination exists. In the example, you can click around to move the sphere, unless you're in baked mode, in which case the sphere must be locked in place to be lit correctly. ## Showcase Baked mode:  Mixed direct mode:  Mixed indirect mode (default):  Real-time mode:  ## Migration guide * The `AmbientLight` resource, the `IrradianceVolume` component, and the `EnvironmentMapLight` component now have `affects_lightmapped_meshes` fields. If you don't need to use that field (for example, if you aren't using lightmaps), you can safely set the field to true. * `DirectionalLight`, `PointLight`, and `SpotLight` now have `affects_lightmapped_mesh_diffuse` fields. If you don't need to use that field (for example, if you aren't using lightmaps), you can safely set the field to true. [glTF Sample Assets]: https://github.com/KhronosGroup/glTF-Sample-Assets/tree/main [Bakery]: https://geom.io/bakery/wiki/index.php?title=Bakery_-_GPU_Lightmapper |
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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.