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This pull request re-submits #10057, which was backed out for breaking macOS, iOS, and Android. I've tested this version on macOS and Android and on the iOS simulator. # Objective This pull request implements *reflection probes*, which generalize environment maps to allow for multiple environment maps in the same scene, each of which has an axis-aligned bounding box. This is a standard feature of physically-based renderers and was inspired by [the corresponding feature in Blender's Eevee renderer]. ## Solution This is a minimal implementation of reflection probes that allows artists to define cuboid bounding regions associated with environment maps. For every view, on every frame, a system builds up a list of the nearest 4 reflection probes that are within the view's frustum and supplies that list to the shader. The PBR fragment shader searches through the list, finds the first containing reflection probe, and uses it for indirect lighting, falling back to the view's environment map if none is found. Both forward and deferred renderers are fully supported. A reflection probe is an entity with a pair of components, *LightProbe* and *EnvironmentMapLight* (as well as the standard *SpatialBundle*, to position it in the world). The *LightProbe* component (along with the *Transform*) defines the bounding region, while the *EnvironmentMapLight* component specifies the associated diffuse and specular cubemaps. A frequent question is "why two components instead of just one?" The advantages of this setup are: 1. It's readily extensible to other types of light probes, in particular *irradiance volumes* (also known as ambient cubes or voxel global illumination), which use the same approach of bounding cuboids. With a single component that applies to both reflection probes and irradiance volumes, we can share the logic that implements falloff and blending between multiple light probes between both of those features. 2. It reduces duplication between the existing *EnvironmentMapLight* and these new reflection probes. Systems can treat environment maps attached to cameras the same way they treat environment maps applied to reflection probes if they wish. Internally, we gather up all environment maps in the scene and place them in a cubemap array. At present, this means that all environment maps must have the same size, mipmap count, and texture format. A warning is emitted if this restriction is violated. We could potentially relax this in the future as part of the automatic mipmap generation work, which could easily do texture format conversion as part of its preprocessing. An easy way to generate reflection probe cubemaps is to bake them in Blender and use the `export-blender-gi` tool that's part of the [`bevy-baked-gi`] project. This tool takes a `.blend` file containing baked cubemaps as input and exports cubemap images, pre-filtered with an embedded fork of the [glTF IBL Sampler], alongside a corresponding `.scn.ron` file that the scene spawner can use to recreate the reflection probes. Note that this is intentionally a minimal implementation, to aid reviewability. Known issues are: * Reflection probes are basically unsupported on WebGL 2, because WebGL 2 has no cubemap arrays. (Strictly speaking, you can have precisely one reflection probe in the scene if you have no other cubemaps anywhere, but this isn't very useful.) * Reflection probes have no falloff, so reflections will abruptly change when objects move from one bounding region to another. * As mentioned before, all cubemaps in the world of a given type (diffuse or specular) must have the same size, format, and mipmap count. Future work includes: * Blending between multiple reflection probes. * A falloff/fade-out region so that reflected objects disappear gradually instead of vanishing all at once. * Irradiance volumes for voxel-based global illumination. This should reuse much of the reflection probe logic, as they're both GI techniques based on cuboid bounding regions. * Support for WebGL 2, by breaking batches when reflection probes are used. These issues notwithstanding, I think it's best to land this with roughly the current set of functionality, because this patch is useful as is and adding everything above would make the pull request significantly larger and harder to review. --- ## Changelog ### Added * A new *LightProbe* component is available that specifies a bounding region that an *EnvironmentMapLight* applies to. The combination of a *LightProbe* and an *EnvironmentMapLight* offers *reflection probe* functionality similar to that available in other engines. [the corresponding feature in Blender's Eevee renderer]: https://docs.blender.org/manual/en/latest/render/eevee/light_probes/reflection_cubemaps.html [`bevy-baked-gi`]: https://github.com/pcwalton/bevy-baked-gi [glTF IBL Sampler]: https://github.com/KhronosGroup/glTF-IBL-Sampler |
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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
- The Bevy Book: Bevy's official documentation. The best place to start learning Bevy.
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- Official Examples: Bevy's dedicated, runnable examples, which are great for digging into specific concepts.
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Before contributing or participating in discussions with the community, you should familiarize yourself with our Code of Conduct.
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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 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.
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.