fixes#2169
Instead of having custom methods with reduced visibility, implement `From<image::DynamicImage> for Texture` and `TryFrom<Texture> for image::DynamicImage`
Since `visible_entities_system` already checks `Visiblie::is_visible` for each entity and requires it to be `true`, there's no reason to verify visibility in `PassNode::prepare` which consumes entities produced by the system.
When implementing `AssetLoader ` you need to specify which File extensions are supported by that loader.
Currently, Bevy always says it supports extensions that actually require activating a Feature beforehand.
This PR adds cf attributes, so Bevy only tries to load those Extensions whose Features were activated.
This prevents Bevy from Panicking and reports such a warning:
```
Jun 02 23:05:57.139 WARN bevy_asset::asset_server: no `AssetLoader` found for the following extension: ogg
```
This also fixes the Bug, that the `png Feature had to be activated even if you wanted to load a different image format.
Fixes#640
`ResMut`, `Mut` and `ReflectMut` all share very similar code for change detection.
This PR is a first pass at refactoring these implementation and removing a lot of the duplicated code.
Note, this introduces a new trait `ChangeDetectable`.
Please feel free to comment away and let me know what you think!
This gets rid of multiple unsafe blocks that we had to maintain ourselves, and instead depends on library that's commonly used and supported by the ecosystem. We also get support for glam types for free.
There is still some things to clear up with the `Bytes` trait, but that is a bit more substantial change and can be done separately. Also there are already separate efforts to use `crevice` crate, so I've just added that as a TODO.
There's what might be considered a proper bug in `PipelineCompiler::compile_pipeline()`, where it overwrites the `step_mode` for the passed in `VertexBufferLayout` with `InputStepMode::Vertex`. Due to this some ugly workarounds are needed to do any kind of instancing.
In the somewhat longer term, `PipelineCompiler::compile_pipeline()` should probably also handle a `Vec<VertexBufferLayout>`, but that would be a (slightly) larger PR, rather than a bugfix. And I'd love to have this fix in sooner than we can deal with a bigger PR.
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
Required by #1429,
- Adds the `Ushort4` vertex attribute for joint indices
- `Mesh::ATTRIBUTE_JOINT_WEIGHT` and `Mesh::ATTRIBUTE_JOINT_INDEX` to import vertex attributes related to skinning from GLTF
- impl `Default` for `Mesh` a empty triangle mesh is created (needed by reflect)
- impl `Reflect` for `Mesh` all attributes are ignored (needed by the animation system)
Changes to get Bevy to compile with wgpu master.
With this, on a Mac:
* 2d examples look fine
* ~~3d examples crash with an error specific to metal about a compilation error~~
* 3d examples work fine after enabling feature `wgpu/cross`
Feature `wgpu/cross` seems to be needed only on some platforms, not sure how to know which. It was introduced in https://github.com/gfx-rs/wgpu-rs/pull/826
Fixes#2037 (and then some)
Problem:
- `TypeUuid`, `RenderResource`, and `Bytes` derive macros did not properly handle generic structs.
Solution:
- Rework the derive macro implementations to handle the generics.
If a mesh without any vertex attributes is rendered (for example, one that only has indices), bevy will crash since the mesh still creates a vertex buffer even though it's empty. Later code assumes that there is vertex data, causing an index-out-of-bounds panic. This PR fixes the issue by adding a check that there is any vertex data before creating a vertex buffer.
I ran into this issue while rendering a tilemap without any vertex attributes (only indices).
Stack trace:
```
thread 'main' panicked at 'index out of bounds: the len is 0 but the index is 0', C:\Dev\Games\bevy\crates\bevy_render\src\render_graph\nodes\pass_node.rs:346:9
stack backtrace:
0: std::panicking::begin_panic_handler
at /rustc/bb491ed23937aef876622e4beb68ae95938b3bf9\/library\std\src\panicking.rs:493
1: core::panicking::panic_fmt
at /rustc/bb491ed23937aef876622e4beb68ae95938b3bf9\/library\core\src\panicking.rs:92
2: core::panicking::panic_bounds_check
at /rustc/bb491ed23937aef876622e4beb68ae95938b3bf9\/library\core\src\panicking.rs:69
3: core::slice::index::{{impl}}::index<core::option::Option<tuple<bevy_render::renderer::render_resource::buffer::BufferId, u64>>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\slice\index.rs:184
4: core::slice::index::{{impl}}::index<core::option::Option<tuple<bevy_render::renderer::render_resource::buffer::BufferId, u64>>,usize>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\slice\index.rs:15
5: alloc::vec::{{impl}}::index<core::option::Option<tuple<bevy_render::renderer::render_resource::buffer::BufferId, u64>>,usize,alloc::alloc::Global>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\alloc\src\vec\mod.rs:2386
6: bevy_render::render_graph::nodes::pass_node::DrawState::is_vertex_buffer_set
at C:\Dev\Games\bevy\crates\bevy_render\src\render_graph\nodes\pass_node.rs:346
7: bevy_render::render_graph::nodes::pass_node::{{impl}}::update::{{closure}}<bevy_render::render_graph::base::MainPass*>
at C:\Dev\Games\bevy\crates\bevy_render\src\render_graph\nodes\pass_node.rs:285
8: bevy_wgpu::renderer::wgpu_render_context::{{impl}}::begin_pass
at C:\Dev\Games\bevy\crates\bevy_wgpu\src\renderer\wgpu_render_context.rs:196
9: bevy_render::render_graph::nodes::pass_node::{{impl}}::update<bevy_render::render_graph::base::MainPass*>
at C:\Dev\Games\bevy\crates\bevy_render\src\render_graph\nodes\pass_node.rs:244
10: bevy_wgpu::renderer::wgpu_render_graph_executor::WgpuRenderGraphExecutor::execute
at C:\Dev\Games\bevy\crates\bevy_wgpu\src\renderer\wgpu_render_graph_executor.rs:75
11: bevy_wgpu::wgpu_renderer::{{impl}}::run_graph::{{closure}}
at C:\Dev\Games\bevy\crates\bevy_wgpu\src\wgpu_renderer.rs:115
12: bevy_ecs::world::World::resource_scope<bevy_render::render_graph::graph::RenderGraph,tuple<>,closure-0>
at C:\Dev\Games\bevy\crates\bevy_ecs\src\world\mod.rs:715
13: bevy_wgpu::wgpu_renderer::WgpuRenderer::run_graph
at C:\Dev\Games\bevy\crates\bevy_wgpu\src\wgpu_renderer.rs:104
14: bevy_wgpu::wgpu_renderer::WgpuRenderer::update
at C:\Dev\Games\bevy\crates\bevy_wgpu\src\wgpu_renderer.rs:121
15: bevy_wgpu::get_wgpu_render_system::{{closure}}
at C:\Dev\Games\bevy\crates\bevy_wgpu\src\lib.rs:112
16: alloc::boxed::{{impl}}::call_mut<tuple<mut bevy_ecs::world::World*>,FnMut<tuple<mut bevy_ecs::world::World*>>,alloc::alloc::Global>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\alloc\src\boxed.rs:1553
17: bevy_ecs::system::exclusive_system::{{impl}}::run
at C:\Dev\Games\bevy\crates\bevy_ecs\src\system\exclusive_system.rs:41
18: bevy_ecs::schedule::stage::{{impl}}::run
at C:\Dev\Games\bevy\crates\bevy_ecs\src\schedule\stage.rs:812
19: bevy_ecs::schedule::Schedule::run_once
at C:\Dev\Games\bevy\crates\bevy_ecs\src\schedule\mod.rs:201
20: bevy_ecs::schedule::{{impl}}::run
at C:\Dev\Games\bevy\crates\bevy_ecs\src\schedule\mod.rs:219
21: bevy_app::app::App::update
at C:\Dev\Games\bevy\crates\bevy_app\src\app.rs:58
22: bevy_winit::winit_runner_with::{{closure}}
at C:\Dev\Games\bevy\crates\bevy_winit\src\lib.rs:485
23: winit::platform_impl::platform::event_loop::{{impl}}::run_return::{{closure}}<tuple<>,closure-1>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop.rs:203
24: alloc::boxed::{{impl}}::call_mut<tuple<winit::event::Event<tuple<>>, mut winit::event_loop::ControlFlow*>,FnMut<tuple<winit::event::Event<tuple<>>, mut winit::event_loop::ControlFlow*>>,alloc::alloc::Global>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\alloc\src\boxed.rs:1553
25: winit::platform_impl::platform::event_loop:🏃:{{impl}}::call_event_handler::{{closure}}<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop\runner.rs:245
26: std::panic::{{impl}}::call_once<tuple<>,closure-0>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panic.rs:344
27: std::panicking::try::do_call<std::panic::AssertUnwindSafe<closure-0>,tuple<>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panicking.rs:379
28: hashbrown::set::HashSet<mut winapi::shared::windef::HWND__*, std::collections:#️⃣:map::RandomState, alloc::alloc::Global>::iter<mut winapi::shared::windef::HWND__*,std::collections:#️⃣:map::RandomState,alloc::alloc::Global>
29: std::panicking::try<tuple<>,std::panic::AssertUnwindSafe<closure-0>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panicking.rs:343
30: std::panic::catch_unwind<std::panic::AssertUnwindSafe<closure-0>,tuple<>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panic.rs:431
31: winit::platform_impl::platform::event_loop:🏃:EventLoopRunner<tuple<>>::catch_unwind<tuple<>,tuple<>,closure-0>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop\runner.rs:152
32: winit::platform_impl::platform::event_loop:🏃:EventLoopRunner<tuple<>>::call_event_handler<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop\runner.rs:239
33: winit::platform_impl::platform::event_loop:🏃:EventLoopRunner<tuple<>>::move_state_to<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop\runner.rs:341
34: winit::platform_impl::platform::event_loop:🏃:EventLoopRunner<tuple<>>::main_events_cleared<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop\runner.rs:227
35: winit::platform_impl::platform::event_loop::flush_paint_messages<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop.rs:676
36: winit::platform_impl::platform::event_loop::thread_event_target_callback::{{closure}}<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop.rs:1967
37: std::panic::{{impl}}::call_once<isize,closure-0>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panic.rs:344
38: std::panicking::try::do_call<std::panic::AssertUnwindSafe<closure-0>,isize>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panicking.rs:379
39: hashbrown::set::HashSet<mut winapi::shared::windef::HWND__*, std::collections:#️⃣:map::RandomState, alloc::alloc::Global>::iter<mut winapi::shared::windef::HWND__*,std::collections:#️⃣:map::RandomState,alloc::alloc::Global>
40: std::panicking::try<isize,std::panic::AssertUnwindSafe<closure-0>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panicking.rs:343
41: std::panic::catch_unwind<std::panic::AssertUnwindSafe<closure-0>,isize>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panic.rs:431
42: winit::platform_impl::platform::event_loop:🏃:EventLoopRunner<tuple<>>::catch_unwind<tuple<>,isize,closure-0>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop\runner.rs:152
43: winit::platform_impl::platform::event_loop::thread_event_target_callback<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop.rs:2151
44: DefSubclassProc
45: DefSubclassProc
46: CallWindowProcW
47: DispatchMessageW
48: SendMessageTimeoutW
49: KiUserCallbackDispatcher
50: NtUserDispatchMessage
51: DispatchMessageW
52: winit::platform_impl::platform::event_loop::EventLoop<tuple<>>::run_return<tuple<>,closure-1>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop.rs:218
53: winit::platform_impl::platform::event_loop::EventLoop<tuple<>>::run<tuple<>,closure-1>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop.rs:188
54: winit::event_loop::EventLoop<tuple<>>::run<tuple<>,closure-1>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\event_loop.rs:154
55: bevy_winit::run<closure-1>
at C:\Dev\Games\bevy\crates\bevy_winit\src\lib.rs:171
56: bevy_winit::winit_runner_with
at C:\Dev\Games\bevy\crates\bevy_winit\src\lib.rs:493
57: bevy_winit::winit_runner
at C:\Dev\Games\bevy\crates\bevy_winit\src\lib.rs:211
58: core::ops::function::Fn::call<fn(bevy_app::app::App),tuple<bevy_app::app::App>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\ops\function.rs:70
59: alloc::boxed::{{impl}}::call<tuple<bevy_app::app::App>,Fn<tuple<bevy_app::app::App>>,alloc::alloc::Global>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\alloc\src\boxed.rs:1560
60: bevy_app::app::App::run
at C:\Dev\Games\bevy\crates\bevy_app\src\app.rs:68
61: bevy_app::app_builder::AppBuilder::run
at C:\Dev\Games\bevy\crates\bevy_app\src\app_builder.rs:54
62: game_main::main
at .\crates\game_main\src\main.rs:23
63: core::ops::function::FnOnce::call_once<fn(),tuple<>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\ops\function.rs:227
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
Apr 27 21:51:01.026 ERROR gpu_descriptor::allocator: `DescriptorAllocator` is dropped while some descriptor sets were not deallocated
error: process didn't exit successfully: `target/cargo\debug\game_main.exe` (exit code: 0xc000041d)
```
There are cases where we want an enum variant name. Right now the only way to do that with rust's std is to derive Debug, but this will also print out the variant's fields. This creates the unfortunate situation where we need to manually write out each variant's string name (ex: in #1963), which is both boilerplate-ey and error-prone. Crates such as `strum` exist for this reason, but it includes a lot of code and complexity that we don't need.
This adds a dead-simple `EnumVariantMeta` derive that exposes `enum_variant_index` and `enum_variant_name` functions. This allows us to make cases like #1963 much cleaner (see the second commit). We might also be able to reuse this logic for `bevy_reflect` enum derives.
In bevy_webgl2, the `RenderResourceContext` is created after startup as it needs to first wait for an event from js side:
f31e5d49de/src/lib.rs (L117)
remove `panic` introduced in #1965 and log as a `warn` instead
This implementations allows you
convert std::vec::Vec<T> to VertexAttributeValues::T and back.
# Examples
```rust
use std::convert::TryInto;
use bevy_render::mesh::VertexAttributeValues;
// creating vector of values
let before = vec![[0_u32; 4]; 10];
let values = VertexAttributeValues::from(before.clone());
let after: Vec<[u32; 4]> = values.try_into().unwrap();
assert_eq!(before, after);
```
Co-authored-by: aloucks <aloucks@cofront.net>
Co-authored-by: simens_green <34134129+simensgreen@users.noreply.github.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
Allows render resources to move data to the heap by boxing them. I did this as a workaround to #1892, but it seems like it'd be useful regardless. If not, feel free to close this PR.
Implements `Byteable` and `RenderResource` for any array containing `Byteable` elements. This allows `RenderResources` to be implemented on structs with arbitrarily-sized arrays, among other things:
```rust
#[derive(RenderResources, TypeUuid)]
#[uuid = "2733ff34-8f95-459f-bf04-3274e686ac5f"]
struct Foo {
buffer: [i32; 256],
}
```
Fixes#1809. It makes it also possible to use `derive` for `SystemParam` inside ECS and avoid manual implementation. An alternative solution to macro changes is to use `use crate as bevy_ecs;` in `event.rs`.
The `VertexBufferLayout` returned by `crates\bevy_render\src\mesh\mesh.rs:308` was unstable, because `HashMap.iter()` has a random order. This caused the pipeline_compiler to wrongly consider a specialization to be different (`crates\bevy_render\src\pipeline\pipeline_compiler.rs:123`), causing each mesh changed event to potentially result in a different `PipelineSpecialization`. This in turn caused `Draw` to emit a `set_pipeline` much more often than needed.
This fix shaves off a `BindPipeline` and two `BindDescriptorSets` (for the Camera and for global renderresources) for every mesh after the first that can now use the same specialization, where it didn't before (which was random).
`StableHashMap` was not a good replacement, because it isn't `Clone`, so instead I replaced it with a `BTreeMap` which is OK in this instance, because there shouldn't be many insertions on `Mesh.attributes` after the mesh is created.
- prints glsl compile error message in multiple lines instead of `thread 'main' panicked at 'called Result::unwrap() on an Err value: Compilation("glslang_shader_parse:\nInfo log:\nERROR: 0:335: \'assign\' : l-value required \"anon@7\" (can\'t modify a uniform)\nERROR: 0:335: \'\' : compilation terminated \nERROR: 2 compilation errors. No code generated.\n\n\nDebug log:\n\n")', crates/bevy_render/src/pipeline/pipeline_compiler.rs:161:22`
- makes gltf error messages have more context
New error:
```rust
thread 'Compute Task Pool (5)' panicked at 'Shader compilation error:
glslang_shader_parse:
Info log:
ERROR: 0:12: 'assign' : l-value required "anon@1" (can't modify a uniform)
ERROR: 0:12: '' : compilation terminated
ERROR: 2 compilation errors. No code generated.
', crates/bevy_render/src/pipeline/pipeline_compiler.rs:364:5
```
These changes are a bit unrelated. I can open separate PRs if someone wants that.
After #1697 I looked at all other Iterators from Bevy and added overrides for `size_hint` where it wasn't done.
Also implemented `ExactSizeIterator` where applicable.
In shaders, `vec3` should be avoided for `std140` layout, as they take the size of a `vec4` and won't support manual padding by adding an additional `float`.
This change is needed for 3D to work in WebGL2. With it, I get PBR to render
<img width="1407" alt="Screenshot 2021-04-02 at 02 57 14" src="https://user-images.githubusercontent.com/8672791/113368551-5a3c2780-935f-11eb-8c8d-e9ba65b5ee98.png">
Without it, nothing renders... @cart Could this be considered for 0.5 release?
Also, I learned shaders 2 days ago, so don't hesitate to correct any issue or misunderstanding I may have
bevy_webgl2 PR in progress for Bevy 0.5 is here if you want to test: https://github.com/rparrett/bevy_webgl2/pull/1
I think [collection, thing_removed_from_collection] is a more natural order than [thing_removed_from_collection, collection]. Just a small tweak that I think we should include in 0.5.
This PR adds normal maps on top of PBR #1554. Once that PR lands, the changes should look simpler.
Edit: Turned out to be so little extra work, I added metallic/roughness texture too. And occlusion and emissive.
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
This PR adds two systems to the sprite module that culls Sprites and AtlasSprites that are not within the camera's view.
This is achieved by removing / adding a new `Viewable` Component dynamically.
Some of the render queries now use a `With<Viewable>` filter to only process the sprites that are actually on screen, which improves performance drastically for scene swith a large amount of sprites off-screen.
https://streamable.com/vvzh2u
This scene shows a map with a 320x320 tiles, with a grid size of 64p.
This is exactly 102400 Sprites in the entire scene.
Without this PR, this scene runs with 1 to 4 FPS.
With this PR..
.. at 720p, there are around 600 visible sprites and runs at ~215 FPS
.. at 1440p there are around 2000 visible sprites and runs at ~135 FPS
The Systems this PR adds take around 1.2ms (with 100K+ sprites in the scene)
Note:
This is only implemented for Sprites and AtlasTextureSprites.
There is no culling for 3D in this PR.
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
This is a rebase of StarArawns PBR work from #261 with IngmarBitters work from #1160 cherry-picked on top.
I had to make a few minor changes to make some intermediate commits compile and the end result is not yet 100% what I expected, so there's a bit more work to do.
Co-authored-by: John Mitchell <toasterthegamer@gmail.com>
Co-authored-by: Ingmar Bitter <ingmar.bitter@gmail.com>
Alternative to #1203 and #1611
Camera bindings have historically been "hacked in". They were _required_ in all shaders and only supported a single Mat4. PBR (#1554) requires the CameraView matrix, but adding this using the "hacked" method forced users to either include all possible camera data in a single binding (#1203) or include all possible bindings (#1611).
This approach instead assigns each "active camera" its own RenderResourceBindings, which are populated by CameraNode. The PassNode then retrieves (and initializes) the relevant bind groups for all render pipelines used by visible entities.
* Enables any number of camera bindings , including zero (with any set or binding number ... set 0 should still be used to avoid rebinds).
* Renames Camera binding to CameraViewProj
* Adds CameraView binding
# Problem Definition
The current change tracking (via flags for both components and resources) fails to detect changes made by systems that are scheduled to run earlier in the frame than they are.
This issue is discussed at length in [#68](https://github.com/bevyengine/bevy/issues/68) and [#54](https://github.com/bevyengine/bevy/issues/54).
This is very much a draft PR, and contributions are welcome and needed.
# Criteria
1. Each change is detected at least once, no matter the ordering.
2. Each change is detected at most once, no matter the ordering.
3. Changes should be detected the same frame that they are made.
4. Competitive ergonomics. Ideally does not require opting-in.
5. Low CPU overhead of computation.
6. Memory efficient. This must not increase over time, except where the number of entities / resources does.
7. Changes should not be lost for systems that don't run.
8. A frame needs to act as a pure function. Given the same set of entities / components it needs to produce the same end state without side-effects.
**Exact** change-tracking proposals satisfy criteria 1 and 2.
**Conservative** change-tracking proposals satisfy criteria 1 but not 2.
**Flaky** change tracking proposals satisfy criteria 2 but not 1.
# Code Base Navigation
There are three types of flags:
- `Added`: A piece of data was added to an entity / `Resources`.
- `Mutated`: A piece of data was able to be modified, because its `DerefMut` was accessed
- `Changed`: The bitwise OR of `Added` and `Changed`
The special behavior of `ChangedRes`, with respect to the scheduler is being removed in [#1313](https://github.com/bevyengine/bevy/pull/1313) and does not need to be reproduced.
`ChangedRes` and friends can be found in "bevy_ecs/core/resources/resource_query.rs".
The `Flags` trait for Components can be found in "bevy_ecs/core/query.rs".
`ComponentFlags` are stored in "bevy_ecs/core/archetypes.rs", defined on line 446.
# Proposals
**Proposal 5 was selected for implementation.**
## Proposal 0: No Change Detection
The baseline, where computations are performed on everything regardless of whether it changed.
**Type:** Conservative
**Pros:**
- already implemented
- will never miss events
- no overhead
**Cons:**
- tons of repeated work
- doesn't allow users to avoid repeating work (or monitoring for other changes)
## Proposal 1: Earlier-This-Tick Change Detection
The current approach as of Bevy 0.4. Flags are set, and then flushed at the end of each frame.
**Type:** Flaky
**Pros:**
- already implemented
- simple to understand
- low memory overhead (2 bits per component)
- low time overhead (clear every flag once per frame)
**Cons:**
- misses systems based on ordering
- systems that don't run every frame miss changes
- duplicates detection when looping
- can lead to unresolvable circular dependencies
## Proposal 2: Two-Tick Change Detection
Flags persist for two frames, using a double-buffer system identical to that used in events.
A change is observed if it is found in either the current frame's list of changes or the previous frame's.
**Type:** Conservative
**Pros:**
- easy to understand
- easy to implement
- low memory overhead (4 bits per component)
- low time overhead (bit mask and shift every flag once per frame)
**Cons:**
- can result in a great deal of duplicated work
- systems that don't run every frame miss changes
- duplicates detection when looping
## Proposal 3: Last-Tick Change Detection
Flags persist for two frames, using a double-buffer system identical to that used in events.
A change is observed if it is found in the previous frame's list of changes.
**Type:** Exact
**Pros:**
- exact
- easy to understand
- easy to implement
- low memory overhead (4 bits per component)
- low time overhead (bit mask and shift every flag once per frame)
**Cons:**
- change detection is always delayed, possibly causing painful chained delays
- systems that don't run every frame miss changes
- duplicates detection when looping
## Proposal 4: Flag-Doubling Change Detection
Combine Proposal 2 and Proposal 3. Differentiate between `JustChanged` (current behavior) and `Changed` (Proposal 3).
Pack this data into the flags according to [this implementation proposal](https://github.com/bevyengine/bevy/issues/68#issuecomment-769174804).
**Type:** Flaky + Exact
**Pros:**
- allows users to acc
- easy to implement
- low memory overhead (4 bits per component)
- low time overhead (bit mask and shift every flag once per frame)
**Cons:**
- users must specify the type of change detection required
- still quite fragile to system ordering effects when using the flaky `JustChanged` form
- cannot get immediate + exact results
- systems that don't run every frame miss changes
- duplicates detection when looping
## [SELECTED] Proposal 5: Generation-Counter Change Detection
A global counter is increased after each system is run. Each component saves the time of last mutation, and each system saves the time of last execution. Mutation is detected when the component's counter is greater than the system's counter. Discussed [here](https://github.com/bevyengine/bevy/issues/68#issuecomment-769174804). How to handle addition detection is unsolved; the current proposal is to use the highest bit of the counter as in proposal 1.
**Type:** Exact (for mutations), flaky (for additions)
**Pros:**
- low time overhead (set component counter on access, set system counter after execution)
- robust to systems that don't run every frame
- robust to systems that loop
**Cons:**
- moderately complex implementation
- must be modified as systems are inserted dynamically
- medium memory overhead (4 bytes per component + system)
- unsolved addition detection
## Proposal 6: System-Data Change Detection
For each system, track which system's changes it has seen. This approach is only worth fully designing and implementing if Proposal 5 fails in some way.
**Type:** Exact
**Pros:**
- exact
- conceptually simple
**Cons:**
- requires storing data on each system
- implementation is complex
- must be modified as systems are inserted dynamically
## Proposal 7: Total-Order Change Detection
Discussed [here](https://github.com/bevyengine/bevy/issues/68#issuecomment-754326523). This proposal is somewhat complicated by the new scheduler, but I believe it should still be conceptually feasible. This approach is only worth fully designing and implementing if Proposal 5 fails in some way.
**Type:** Exact
**Pros:**
- exact
- efficient data storage relative to other exact proposals
**Cons:**
- requires access to the scheduler
- complex implementation and difficulty grokking
- must be modified as systems are inserted dynamically
# Tests
- We will need to verify properties 1, 2, 3, 7 and 8. Priority: 1 > 2 = 3 > 8 > 7
- Ideally we can use identical user-facing syntax for all proposals, allowing us to re-use the same syntax for each.
- When writing tests, we need to carefully specify order using explicit dependencies.
- These tests will need to be duplicated for both components and resources.
- We need to be sure to handle cases where ambiguous system orders exist.
`changing_system` is always the system that makes the changes, and `detecting_system` always detects the changes.
The component / resource changed will be simple boolean wrapper structs.
## Basic Added / Mutated / Changed
2 x 3 design:
- Resources vs. Components
- Added vs. Changed vs. Mutated
- `changing_system` runs before `detecting_system`
- verify at the end of tick 2
## At Least Once
2 x 3 design:
- Resources vs. Components
- Added vs. Changed vs. Mutated
- `changing_system` runs after `detecting_system`
- verify at the end of tick 2
## At Most Once
2 x 3 design:
- Resources vs. Components
- Added vs. Changed vs. Mutated
- `changing_system` runs once before `detecting_system`
- increment a counter based on the number of changes detected
- verify at the end of tick 2
## Fast Detection
2 x 3 design:
- Resources vs. Components
- Added vs. Changed vs. Mutated
- `changing_system` runs before `detecting_system`
- verify at the end of tick 1
## Ambiguous System Ordering Robustness
2 x 3 x 2 design:
- Resources vs. Components
- Added vs. Changed vs. Mutated
- `changing_system` runs [before/after] `detecting_system` in tick 1
- `changing_system` runs [after/before] `detecting_system` in tick 2
## System Pausing
2 x 3 design:
- Resources vs. Components
- Added vs. Changed vs. Mutated
- `changing_system` runs in tick 1, then is disabled by run criteria
- `detecting_system` is disabled by run criteria until it is run once during tick 3
- verify at the end of tick 3
## Addition Causes Mutation
2 design:
- Resources vs. Components
- `adding_system_1` adds a component / resource
- `adding system_2` adds the same component / resource
- verify the `Mutated` flag at the end of the tick
- verify the `Added` flag at the end of the tick
First check tests for: https://github.com/bevyengine/bevy/issues/333
Second check tests for: https://github.com/bevyengine/bevy/issues/1443
## Changes Made By Commands
- `adding_system` runs in Update in tick 1, and sends a command to add a component
- `detecting_system` runs in Update in tick 1 and 2, after `adding_system`
- We can't detect the changes in tick 1, since they haven't been processed yet
- If we were to track these changes as being emitted by `adding_system`, we can't detect the changes in tick 2 either, since `detecting_system` has already run once after `adding_system` :(
# Benchmarks
See: [general advice](https://github.com/bevyengine/bevy/blob/master/docs/profiling.md), [Criterion crate](https://github.com/bheisler/criterion.rs)
There are several critical parameters to vary:
1. entity count (1 to 10^9)
2. fraction of entities that are changed (0% to 100%)
3. cost to perform work on changed entities, i.e. workload (1 ns to 1s)
1 and 2 should be varied between benchmark runs. 3 can be added on computationally.
We want to measure:
- memory cost
- run time
We should collect these measurements across several frames (100?) to reduce bootup effects and accurately measure the mean, variance and drift.
Entity-component change detection is much more important to benchmark than resource change detection, due to the orders of magnitude higher number of pieces of data.
No change detection at all should be included in benchmarks as a second control for cases where missing changes is unacceptable.
## Graphs
1. y: performance, x: log_10(entity count), color: proposal, facet: performance metric. Set cost to perform work to 0.
2. y: run time, x: cost to perform work, color: proposal, facet: fraction changed. Set number of entities to 10^6
3. y: memory, x: frames, color: proposal
# Conclusions
1. Is the theoretical categorization of the proposals correct according to our tests?
2. How does the performance of the proposals compare without any load?
3. How does the performance of the proposals compare with realistic loads?
4. At what workload does more exact change tracking become worth the (presumably) higher overhead?
5. When does adding change-detection to save on work become worthwhile?
6. Is there enough divergence in performance between the best solutions in each class to ship more than one change-tracking solution?
# Implementation Plan
1. Write a test suite.
2. Verify that tests fail for existing approach.
3. Write a benchmark suite.
4. Get performance numbers for existing approach.
5. Implement, test and benchmark various solutions using a Git branch per proposal.
6. Create a draft PR with all solutions and present results to team.
7. Select a solution and replace existing change detection.
Co-authored-by: Brice DAVIER <bricedavier@gmail.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
