a8f15bd95e
Currently, our batchable binned items are stored in a hash table that maps bin key, which includes the batch set key, to a list of entities. Multidraw is handled by sorting the bin keys and accumulating adjacent bins that can be multidrawn together (i.e. have the same batch set key) into multidraw commands during `batch_and_prepare_binned_render_phase`. This is reasonably efficient right now, but it will complicate future work to retain indirect draw parameters from frame to frame. Consider what must happen when we have retained indirect draw parameters and the application adds a bin (i.e. a new mesh) that shares a batch set key with some pre-existing meshes. (That is, the new mesh can be multidrawn with the pre-existing meshes.) To be maximally efficient, our goal in that scenario will be to update *only* the indirect draw parameters for the batch set (i.e. multidraw command) containing the mesh that was added, while leaving the others alone. That means that we have to quickly locate all the bins that belong to the batch set being modified. In the existing code, we would have to sort the list of bin keys so that bins that can be multidrawn together become adjacent to one another in the list. Then we would have to do a binary search through the sorted list to find the location of the bin that was just added. Next, we would have to widen our search to adjacent indexes that contain the same batch set, doing expensive comparisons against the batch set key every time. Finally, we would reallocate the indirect draw parameters and update the stored pointers to the indirect draw parameters that the bins store. By contrast, it'd be dramatically simpler if we simply changed the way bins are stored to first map from batch set key (i.e. multidraw command) to the bins (i.e. meshes) within that batch set key, and then from each individual bin to the mesh instances. That way, the scenario above in which we add a new mesh will be simpler to handle. First, we will look up the batch set key corresponding to that mesh in the outer map to find an inner map corresponding to the single multidraw command that will draw that batch set. We will know how many meshes the multidraw command is going to draw by the size of that inner map. Then we simply need to reallocate the indirect draw parameters and update the pointers to those parameters within the bins as necessary. There will be no need to do any binary search or expensive batch set key comparison: only a single hash lookup and an iteration over the inner map to update the pointers. This patch implements the above technique. Because we don't have retained bins yet, this PR provides no performance benefits. However, it opens the door to maximally efficient updates when only a small number of meshes change from frame to frame. The main churn that this patch causes is that the *batch set key* (which uniquely specifies a multidraw command) and *bin key* (which uniquely specifies a mesh *within* that multidraw command) are now separate, instead of the batch set key being embedded *within* the bin key. In order to isolate potential regressions, I think that at least #16890, #16836, and #16825 should land before this PR does. ## Migration Guide * The *batch set key* is now separate from the *bin key* in `BinnedPhaseItem`. The batch set key is used to collect multidrawable meshes together. If you aren't using the multidraw feature, you can safely set the batch set key to `()`. |
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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.