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# Objective - Faster meshlet rasterization path for small triangles - Avoid having to allocate and write out a triangle buffer - Refactor gpu_scene.rs ## Solution - Replace the 32bit visbuffer texture with a 64bit visbuffer buffer, where the left 32 bits encode depth, and the right 32 bits encode the existing cluster + triangle IDs. Can't use 64bit textures, wgpu/naga doesn't support atomic ops on textures yet. - Instead of writing out a buffer of packed cluster + triangle IDs (per triangle) to raster, the culling pass now writes out a buffer of just cluster IDs (per cluster, so less memory allocated, cheaper to write out). - Clusters for software raster are allocated from the left side - Clusters for hardware raster are allocated in the same buffer, from the right side - The buffer size is fixed at MeshletPlugin build time, and should be set to a reasonable value for your scene (no warning on overflow, and no good way to determine what value you need outside of renderdoc - I plan to fix this in a future PR adding a meshlet stats overlay) - Currently I don't have a heuristic for software vs hardware raster selection for each cluster. The existing code is just a placeholder. I need to profile on a release scene and come up with a heuristic, probably in a future PR. - The culling shader is getting pretty hard to follow at this point, but I don't want to spend time improving it as the entire shader/pass is getting rewritten/replaced in the near future. - Software raster is a compute workgroup per-cluster. Each workgroup loads and transforms the <=64 vertices of the cluster, and then rasterizes the <=64 triangles of the cluster. - Two variants are implemented: Scanline for clusters with any larger triangles (still smaller than hardware is good at), and brute-force for very very tiny triangles - Once the shader determines that a pixel should be filled in, it does an atomicMax() on the visbuffer to store the results, copying how Nanite works - On devices with a low max workgroups per dispatch limit, an extra compute pass is inserted before software raster to convert from a 1d to 2d dispatch (I don't think 3d would ever be necessary). - I haven't implemented the top-left rule or subpixel precision yet, I'm leaving that for a future PR since I get usable results without it for now - Resources used: https://kristoffer-dyrkorn.github.io/triangle-rasterizer and chapters 6-8 of https://fgiesen.wordpress.com/2013/02/17/optimizing-sw-occlusion-culling-index - Hardware raster now spawns 64*3 vertex invocations per meshlet, instead of the actual meshlet vertex count. Extra invocations just early-exit. - While this is slower than the existing system, hardware draws should be rare now that software raster is usable, and it saves a ton of memory using the unified cluster ID buffer. This would be fixed if wgpu had support for mesh shaders. - Instead of writing to a color+depth attachment, the hardware raster pass also does the same atomic visbuffer writes that software raster uses. - We have to bind a dummy render target anyways, as wgpu doesn't currently support render passes without any attachments - Material IDs are no longer written out during the main rasterization passes. - If we had async compute queues, we could overlap the software and hardware raster passes. - New material and depth resolve passes run at the end of the visbuffer node, and write out view depth and material ID depth textures ### Misc changes - Fixed cluster culling importing, but never actually using the previous view uniforms when doing occlusion culling - Fixed incorrectly adding the LOD error twice when building the meshlet mesh - Splitup gpu_scene module into meshlet_mesh_manager, instance_manager, and resource_manager - resource_manager is still too complex and inefficient (extract and prepare are way too expensive). I plan on improving this in a future PR, but for now ResourceManager is mostly a 1:1 port of the leftover MeshletGpuScene bits. - Material draw passes have been renamed to the more accurate material shade pass, as well as some other misc renaming (in the future, these will be compute shaders even, and not actual draw calls) --- ## Migration Guide - TBD (ask me at the end of the release for meshlet changes as a whole) --------- Co-authored-by: vero <email@atlasdostal.com> |
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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.