Commit graph

1612 commits

Author SHA1 Message Date
Robert Swain
b809e8e931 bevy_pbr: Fix ClusterConfig::None (#4483)
# Objective

- Fix `ClusterConfig::None`
- This fix is from @robtfm but they didn't have time to submit it, so I am.

## Solution

- Always clear clusters and skip processing when `ClusterConfig::None`
- Conditionally remove `VisiblePointLights` from the view if it is present
2022-04-15 16:05:59 +00:00
Daniel McNab
424d4d26f1 A hack to work around minimising still being broken (#4481)
# Objective

- https://github.com/bevyengine/bevy/pull/4098 still hasn't fixed minimisation on Windows.
- `Clusters.lights` is assumed to have the number of items given by the product of `Clusters.dimensions`'s axes.

## Solution

- Make that true in `clear`.
2022-04-15 11:22:48 +00:00
Dusty DeWeese
0d2b527faf Avoid windows with a physical size of zero (#4098)
# Objective

Fix #4097

## Solution

Return `None` from `RenderTarget::get_physical_size` if either dimension is zero.
2022-04-15 07:32:21 +00:00
Hennadii Chernyshchyk
3b81a50a1a Fix crash in headless mode (#4476)
# Objective

Fixes #4440.

## Solution

Check if `RenderDevice` exists and add CI validation.
2022-04-15 07:13:37 +00:00
Robert Swain
c2a9d5843d Faster assign lights to clusters (#4345)
# Objective

- Fixes #4234
- Fixes #4473 
- Built on top of #3989
- Improve performance of `assign_lights_to_clusters`

## Solution

- Remove the OBB-based cluster light assignment algorithm and calculation of view space AABBs
- Implement the 'iterative sphere refinement' algorithm used in Just Cause 3 by Emil Persson as documented in the Siggraph 2015 Practical Clustered Shading talk by Persson, on pages 42-44 http://newq.net/dl/pub/s2015_practical.pdf
- Adapt to also support orthographic projections
- Add `many_lights -- orthographic` for testing many lights using an orthographic projection

## Results

- `assign_lights_to_clusters` in `many_lights` before this PR on an M1 Max over 1500 frames had a median execution time of 1.71ms. With this PR it is 1.51ms, a reduction of 0.2ms or 11.7% for this system.

---

## Changelog

- Changed: Improved cluster light assignment performance

Co-authored-by: robtfm <50659922+robtfm@users.noreply.github.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2022-04-15 02:53:20 +00:00
François
d37cde8f1a fix feature location from #3851 (#4477)
# Objective

- in #3851, a feature for tracing was added to bevy_transform
- usage of that feature was moved to bevy_hierarchy, but the feature was not updated

## Solution

- add the feature to bevy_hierarchy, remove it from bevy_transform
2022-04-14 21:16:03 +00:00
François
8630b194dc add more logs when despawning entities (#3851)
# Objective

- Provide more information when despawning an entity

## Solution

- Add a debug log when despawning an entity
- Add spans to the recursive ways of despawning an entity

```sh
RUST_LOG=debug cargo run --example panic --features trace
# RUST_LOG=debug needed to show debug logs from bevy_ecs
# --features trace needed to have the extra spans
...

DEBUG bevy_app:frame:stage{name=Update}:system_commands{name="panic::despawn_parent"}:command{name="DespawnRecursive" entity=0v0}: bevy_ecs::world: Despawning entity 1v0
DEBUG bevy_app:frame:stage{name=Update}:system_commands{name="panic::despawn_parent"}:command{name="DespawnRecursive" entity=0v0}: bevy_ecs::world: Despawning entity 0v0
```
2022-04-13 23:35:28 +00:00
Christian Hughes
16133de8cd WorldQuery derive macro now respects visibility (#4125)
## Objective

Fixes #4122.

## Solution

Inherit the visibility of the struct being derived for the `xxItem`, `xxFetch`, `xxState` structs.

Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2022-04-13 21:50:45 +00:00
Martin Dickopp
995f85e157 Fix typos in Time::last_update and Time::time_since_startup documentation (#4470)
# Objective

The documentation of the `Time::last_update` and `Time::time_since_startup` methods contains typos. It uses apostrophe instead of backtick characters around `Instant` and `Duration`, so that these words are not recognized as identifiers in the generated API documentation. This should be fixed.

## Solution

Fix the typos.
2022-04-13 21:34:21 +00:00
Johannes Hackel
621f3969c7 Switch render order to 2d-on-top-of-3d (#4467)
Because #3552 got merged only switching the render order is left to fix #3902
2022-04-13 20:05:34 +00:00
Carter Anderson
8783fae7de Use "many" instead of "multiple" consistently (#4463)
We missed a couple of these renames in #4384
2022-04-13 00:35:47 +00:00
Dusty DeWeese
5a297d7903 Reuse texture when resolving multiple passes (#3552)
# Objective

Fixes https://github.com/bevyengine/bevy/issues/3499

## Solution

Uses a `HashMap` from `RenderTarget` to sampled textures when preparing `ViewTarget`s to ensure that two passes with the same render target get sampled to the same texture.

This builds on and depends on https://github.com/bevyengine/bevy/pull/3412, so this will be a draft PR until #3412 is merged. All changes for this PR are in the last commit.
2022-04-12 19:27:30 +00:00
Jakob Hellermann
193e8c4ada scene_viewer: load cameras (#4425)
# Objective

glTF files can contain cameras. Currently the scene viewer example uses _a_ camera defined in the file if possible, otherwise it spawns a new one. It would be nice if instead it could load all the cameras and cycle through them, while also having a separate user-controller camera.

## Solution

- instead of just a camera that is already defined, always spawn a new separate user-controller camera
- maintain a list of loaded cameras and cycle through them (wrapping to the user-controller camera) when pressing `C`

This matches the behavious that https://github.khronos.org/glTF-Sample-Viewer-Release/ has.

## Implementation notes

- The gltf scene asset loader just spawns the cameras into the world, but does not return a mapping of camera index to bevy entity. So instead the scene_viewer example just collects all spawned cameras with a good old `query.iter().collect()`, so the order is unspecified and may change between runs.

## Demo

https://user-images.githubusercontent.com/22177966/161826637-40161482-5b3b-4df5-aae8-1d5e9b918393.mp4


using the virtual city glTF sample file: https://github.com/KhronosGroup/glTF-Sample-Models/tree/master/2.0/VC

Co-authored-by: Jakob Hellermann <hellermann@sipgate.de>
2022-04-11 22:56:06 +00:00
François
e8cd2fc727 Audio control at start of playback (#4110)
# Objective

- While playing with volume, I noticed that when setting the volume just after playback start, I still get a few milliseconds at normal volume

## Solution

- Replace `play_in_loop` with `play_with_settings` that allows from more controls
- Adds a `PlaybackSettings` to specify the settings from start. Can be used: `PlaybackSettings::LOOP.with_volume(0.75)`
2022-04-08 23:12:30 +00:00
Jakob Hellermann
c12ee81822 bevy_app: add tracing event with tracy.frame_mark (#4320)
Currently `tracy` interprets the entire trace as one frame because the marker for frames isn't being recorded.

~~When an event with `tracy.trace_marker=true` is recorded, `tracing-tracy` will mark the frame as finished:
<aa0b96b2ae/tracing-tracy/src/lib.rs (L240)>~~

~~Unfortunately this leads to~~
```rs
INFO bevy_app:frame: bevy_app::app: finished frame tracy.frame_mark=true
```
~~being printed every frame (we can't use DEBUG because bevy_log sets `max_release_level_info`.~~

Instead of emitting an event that gets logged every frame, we can depend on tracy-client itself and call `finish_continuous_frame!();`
2022-04-08 22:50:23 +00:00
Kirillov Kirill
3756181e23 Change scaling mode to FixedHorizontal (#4055)
# Objective

- Fixes the issue with orthographic camera imported from glTF not displaying anything (mentioned in #4005).

## Solution

- This was due to wrong scaling mode being used. This PR simply changes WindowSize scaling mode to FixedHorizontal.

## Important Note

Currently, othographic scale in Blender, three.js, and possibly other software does not translate to Bevy (via glTF) because their developers have [misinterpreted the spec](https://github.com/KhronosGroup/glTF/issues/1663#issuecomment-618194015). The camera parameters have been clarified in glTF 2.0, which was released on October of 2021. In Blender 3.0.1 this issue has **not** been fixed yet. If you are importing orthographic cameras from Blender, you have to divide the scale by 2.
2022-04-08 17:28:32 +00:00
harudagondi
64d217823d Allow iter combinations on queries with filters (#3656)
# Objective

- Previously, `iter_combinations()` does not work on queries that have filters.
- Fixes #3651

## Solution

- Derived Copy on all `*Fetch<T>` structs, and manually implemented `Clone` to allow the test to pass (`.count()` does not work on `QueryCombinationIter` when `Clone` is derived)


Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2022-04-08 00:21:24 +00:00
Kirillov Kirill
01bdf67c33 Improve the set_active_camera system (#4251)
# Objective

- Make `set_active_camera` system correctly respond to camera deletion, while preserving its correct behavior on first ever frame and any consequent frame, and with multiple cameras of the same type available in the world.
- Fixes #4227

## Solution

- Add a check that the entity referred to by `ActiveCamera` still exists in the world.
2022-04-07 23:30:47 +00:00
François
d478723e19 insert the gltf mesh name on the entity if there is one (#4119)
# Objective

- In glTF, mesh can be named. This named is used to be able to reference the mesh, but not as a component on the entity
- Bevy only added the node name to the parent node.


## Solution

- Also adds the name on the mesh entity if there is one.

Limitation: In glTF, it's possible to have one mesh (which can be named) corresponding to several primitives (which can't, but are the actual mesh). I added the mesh name to the entity with the `PbrBundle` matching the primitives, which means that a mesh with several primitives would all have the same name. I think this is acceptable...
2022-04-07 22:19:32 +00:00
François
4feb0d520a increase the maximum number of point lights with shadows to the max supported by the device (#4435)
# Objective

- Being limited to 10 pointlights with shadow is very limiting

## Solution

- Raise the limit
2022-04-07 21:55:31 +00:00
François
8268e7fa9e expose extras from gltf nodes (#2154)
fixes #2153 

expose the `extras` field value as a string
2022-04-07 21:30:52 +00:00
Torne Wuff
b1afe2dcca Make System responsible for updating its own archetypes (#4115)
# Objective

- Make it possible to use `System`s outside of the scheduler/executor without having to define logic to track new archetypes and call `System::add_archetype()` for each.

## Solution

- Replace `System::add_archetype(&Archetype)` with `System::update_archetypes(&World)`, making systems responsible for tracking their own most recent archetype generation the way that `SystemState` already does.

This has minimal (or simplifying) effect on most of the code with the exception of `FunctionSystem`, which must now track the latest `ArchetypeGeneration` it saw instead of relying on the executor to do it.

Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2022-04-07 20:50:43 +00:00
Gabriel Bourgeois
6f16580b8a Fix clicked UI nodes getting reset when hovering child nodes (#4194)
# Objective

Fixes #4193

## Solution

When resetting a node's `Interaction` to `None`, ignore any `Clicked` node because that should be handled by the mouse release check exclusively.
2022-04-07 19:08:09 +00:00
Daniel McNab
21a875d67b Some small changes related to run criteria piping (#3923)
Remove the 'chaining' api, as it's peculiar

~~Implement the label traits for `Box<dyn ThatTrait>` (n.b. I'm not confident about this change, but it was the quickest path to not regressing)~~

Remove the need for '`.system`' when using run criteria piping
2022-04-07 19:08:08 +00:00
François
9d54f33974 Skinned extraction speedup (#4428)
# Objective

- While animating 501 https://github.com/KhronosGroup/glTF-Sample-Models/tree/master/2.0/BrainStem, I noticed things were getting a little slow
- Looking in tracy, the system `extract_skinned_meshes` is taking a lot of time, with a mean duration of 15.17ms

## Solution

- ~~Use `Vec` instead of a `SmallVec`~~
- ~~Don't use an temporary variable~~
- Compute the affine matrix as an `Affine3A` instead
- Remove the `temp` vec

| |mean|
|---|---|
|base|15.17ms|
|~~vec~~|~~9.31ms~~|
|~~no temp variable~~|~~11.31ms~~|
|removing the temp vector|8.43ms|
|affine|13.21ms|
|all together|7.23ms|
2022-04-07 16:16:36 +00:00
Robert Swain
c5963b4fd5 Use storage buffers for clustered forward point lights (#3989)
# Objective

- Make use of storage buffers, where they are available, for clustered forward bindings to support far more point lights in a scene
- Fixes #3605 
- Based on top of #4079 

This branch on an M1 Max can keep 60fps with about 2150 point lights of radius 1m in the Sponza scene where I've been testing. The bottleneck is mostly assigning lights to clusters which grows faster than linearly (I think 1000 lights was about 1.5ms and 5000 was 7.5ms). I have seen papers and presentations leveraging compute shaders that can get this up to over 1 million. That said, I think any further optimisations should probably be done in a separate PR.

## Solution

- Add `RenderDevice` to the `Material` and `SpecializedMaterial` trait `::key()` functions to allow setting flags on the keys depending on feature/limit availability
- Make `GpuPointLights` and `ViewClusterBuffers` into enums containing `UniformVec` and `StorageBuffer` variants. Implement the necessary API on them to make usage the same for both cases, and the only difference is at initialisation time.
- Appropriate shader defs in the shader code to handle the two cases

## Context on some decisions / open questions

- I'm using `max_storage_buffers_per_shader_stage >= 3` as a check to see if storage buffers are supported. I was thinking about diving into 'binding resource management' but it feels like we don't have enough use cases to understand the problem yet, and it is mostly a separate concern to this PR, so I think it should be handled separately.
- Should `ViewClusterBuffers` and `ViewClusterBindings` be merged, duplicating the count variables into the enum variants?


Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2022-04-07 16:16:35 +00:00
Robert Swain
579928e8e0 bevy_pbr: Support flipping tangent space normal map y for DirectX normal maps (#4433)
# Objective

- Normal maps authored for DirectX use a left-handed convention and have their tangent space normal in the texture inverted from what we need. Support this.
- Details here: https://doc.babylonjs.com/divingDeeper/materials/advanced/normalMaps

## Solution

- Add a `StandardMaterial` `flip_normal_map_y` boolean field
- Add a `STANDARDMATERIAL_FLIP_NORMAL_MAP_Y` flag to `StandardMaterialFlags` and in the PBR shader
- Flip the y-component of the tangent space normal just after sampling it from the normal map texture

## Screenshots

### Before

<img width="1392" alt="Screenshot 2022-04-06 at 21 04 44" src="https://user-images.githubusercontent.com/302146/162050314-e7bfaaf6-9ee1-4756-9821-f6f5ff78f508.png">

### After

<img width="1392" alt="Screenshot 2022-04-06 at 21 03 39" src="https://user-images.githubusercontent.com/302146/162050255-36ee0745-1d79-4fd2-9a1c-18085376b643.png">

---

## Changelog

- Added: Support for flipping the normal map texture y component for normal maps authored for use with DirectX
2022-04-07 15:50:14 +00:00
KDecay
f907d67d7e Fix formatting, spelling, phrasing and consistency (#4275)
# Objective

The `bevy_app` crate has a lot of inconsistencies in the documentation (formatting, spelling, phrasing, consistency).

## Solution

Make it more consistent.
2022-04-05 22:36:02 +00:00
François
30878e3a7d add AnimationPlayer component only on scene roots that are also animation roots (#4417)
# Objective

- Fix #4416 
- The scene has two root nodes, with the second one being the animation root

## Solution

- Check all scene root nodes, and add the `AnimationPlayer` component to nodes that are also animation roots
2022-04-05 21:52:00 +00:00
TheRawMeatball
73edb11db6 Add more FromWorld implementations (#3945)
# Objective

Make `FromWorld` more useful for abstractions with a form similar to
```rs
trait FancyAbstraction {
  type PreInitializedData: FromWorld;
}
```

## Solution

Add a `FromWorld` implementation for `SystemState` as well as a way to group together multiple `FromWorld` implementing types as one.

Note: I plan to follow up this PR with another to add `Local` support to exclusive systems, which should get a fair amount of use from the `FromWorld` implementation on `SystemState`.
2022-04-05 20:04:34 +00:00
Hennadii Chernyshchyk
ea6e6f7db2 Do not crash if RenderDevice doesn't exist (#4427)
# Objective

Avoid crashing if `RenderDevice` doesn't exist (required for headless mode).
Fixes #4392.

## Solution

Use `CompressedImageFormats::all()` if there is no `RenderDevice`.
2022-04-05 19:37:23 +00:00
Alice Cecile
dbb2fcb677 Re-enable test_property_type_registration() (#4419)
# Objective

- This test was mysteriously commented out

## Solution

- Re-enable it
- Also done in #4299, but this is better as its own PR.
2022-04-05 18:34:27 +00:00
François
cf831d5185 input clear should not clear pressed (#4418)
# Objective

- Revert #4410 
- `Input<T>.clear()` is the method call at the end of each frame for inputs. Clearing `pressed` in it mean that checking if a key is pressed will always return false
2022-04-04 22:10:00 +00:00
François
8e864fdd18 can specify an anchor for a sprite (#3463)
# Objective

- Fixes #1616, fixes #2225
- Let user specify an anchor for a sprite

## Solution

- Add an enum for an anchor point for most common values, with a variant for a custom point
- Defaults to Center to not change current behaviour


Co-authored-by: François <8672791+mockersf@users.noreply.github.com>
2022-04-04 22:09:59 +00:00
Boxy
dba7790012 REMOVE unsound lifetime annotations on EntityMut (#4096)
Fixes #3408
#3001 also solves this but I dont see it getting merged any time soon so...
# Objective
make bevy ecs a lil bit less unsound

## Solution
make `EntityMut::get_component_mut` return borrows from self instead of `'w`
2022-04-04 21:33:33 +00:00
François
703ae5df5d gltf: add a name to nodes without names (#4396)
# Objective

- Animation is using `Name` to be able to address nodes in an entity free way
- When loading random animated gltf files, I noticed some had animations without names sometimes

## Solution

- Add default names to all nodes
2022-04-04 20:26:11 +00:00
Troels Jessen
d9d2fb6409 Added pressed state to input clear so it clears everything (#4410)
# Objective

Adds `pressed` state to Input::clear(). Fixes #3383
2022-04-04 20:09:55 +00:00
Lukas Wirth
39d89fe0df Enable drag-and-drop events on windows (#3772)
# Objective

- Fixes https://github.com/bevyengine/bevy/issues/2096

## Solution

- This PR enables the drag-and-drop feature for winit on windows again, as the collision issue between cpal and winit has been fixed in https://github.com/RustAudio/cpal/pull/597. I confirmed the drag and drop example working on windows 10 with this change.
- ~~It also bumps the rodio version, though this is not strictly necessary.~~
2022-04-04 20:09:54 +00:00
François
5e70ad96c6 animations: don't ignore curves with one keyframe (#4406)
# Objective

- While playing with animated models, I noticed some were a little off

## Solution

- Some animations curves only have one keyframe, they are used to set a transform to a given value
- Those were ignored as we're never exactly at the ts 0.0 of an animation. going there explicitly (`.set_elapsed(0.0).pause()`) would crash
- Special case this as there isn't much to animate in this case
2022-04-04 19:45:51 +00:00
TheRawMeatball
032b0f4bac Fix derive(SystemParam) macro (#4400)
Fixes the issue seen in #4398
2022-04-04 19:22:28 +00:00
Francesco Giordana
dbd5e7ab6b Fixed case of R == G, following original conversion formula (#4383)
https://en.wikipedia.org/wiki/HSL_and_HSV#From_RGB

# Objective
Fixes #4382

## Solution

- Describe the solution used to achieve the objective above.
Fixed conversion formula to account for red and green component being max and equal
---

## Changelog
Fixed RGB -> HSL colorspace conversion

## Migration Guide


Co-authored-by: Francesco Giordana <fgiordana@netflix.com>
2022-04-04 18:59:00 +00:00
KDecay
f90da74e32 Remove face_toward.rs (#4277)
# Objective

- Part of the splitting process of #3503.

## Solution

- Remove the `face_toward.rs` file containing the `FaceToward` trait.

## Reasons

- It is unused inside of `bevy`.
- The method `Mat4::face_toward` of the trait is identical to `Mat4::look_at_rh` (see https://docs.rs/glam/latest/glam/f32/struct.Mat4.html#method.look_at_rh).
- Discussion in #3503.

## Changelog

### Removed

- The `FaceToward` trait got removed.

## Migration Guide

-  The `FaceToward` trait got removed. To migrate you just have to change every occurrence of `Mat4::face_toward` to `Mat4::look_at_rh`.
2022-04-03 14:40:46 +00:00
François
449a1d223c animation player (#4375)
# Objective

- Add a basic animation player
  - Single track
  - Not generic, can only animate `Transform`s
  - With plenty of possible optimisations available
  - Close-ish to https://github.com/bevyengine/rfcs/pull/49
- https://discord.com/channels/691052431525675048/774027865020039209/958820063148929064

## Solution

- Can play animations
  - looping or not
- Can pause animations
- Can seek in animation
- Can alter speed of animation
- I also removed the previous gltf animation example

https://user-images.githubusercontent.com/8672791/161051887-e79283f0-9803-448a-93d0-5f7a62acb02d.mp4
2022-04-02 22:36:02 +00:00
Daniel McNab
c26be39719 Remove unnecessary system labels (#4340)
# Objective

- Since #4224, using labels which only refer to one system doesn't make sense.

## Solution

- Remove some of those.

## Future work

- We should remove the ability to use strings as system labels entirely. I haven't in this PR because there are tests which use this, and that's a lot of code to change.
   - The only use cases for labels are either intra-crate, which use #4224, or inter-crate, which should either use #4224 or explicit types. Neither of those should use strings.
2022-04-01 21:11:05 +00:00
Light Ning
dd2001f2f1 bevy_render: add a small color box to each color (#4387)
# Objective

- bevy_render: add a small color box to each color

## Solution

![bevy_color_doc](https://user-images.githubusercontent.com/1318472/161241226-e7632a90-f526-44de-a68e-ff63b848164b.png)

---

## Changelog
2022-04-01 20:52:22 +00:00
Alice Cecile
b33dae31ec Rename get_multiple APIs to get_many (#4384)
# Objective

-  std's new APIs do the same thing as `Query::get_multiple_mut`, but are called `get_many`: https://github.com/rust-lang/rust/pull/83608

## Solution

- Find and replace `get_multiple` with `get_many`
2022-03-31 20:59:26 +00:00
devil ira
48ac955afd Fix loading non-TriangleList meshes without normals in gltf loader (#4376)
# Objective
Make it so that loading in a mesh without normals that is not a `TriangleList` succeeds.

## Solution
Flat normals can only be calculated on a mesh made of triangles.
Check whether the mesh is a `TriangleList` before trying to compute missing normals.

## Additional changes
The panic condition in `duplicate_vertices` did not make sense to me. I moved it to `compute_flat_normals` where the algorithm would produce incorrect results if the mesh is not a `TriangleList`.

Co-authored-by: devil-ira <justthecooldude@gmail.com>
2022-03-31 20:43:01 +00:00
Daniel McNab
aca7fc1854 Remove outdated perf comments (#4374)
# Objective

- The perf comments, added (by me) in https://github.com/bevyengine/bevy/pull/1349, became outdated once the initialisation call started to take an exclusive reference, (presumably in https://github.com/bevyengine/bevy/pull/1525).
- They have been naïvely transferred along ever since

## Solution

- Remove them
2022-03-31 20:43:00 +00:00
SecretPocketCat
3af90b67a6 Update RemovedComponents doc comment (#4373)
# Objective

- Clarify `RemovedComponents` are flushed in `CoreStage::Last` and systems relying on that should run before that stage

## Solution

- Update `RemovedComponents` doc comment
2022-03-31 20:24:32 +00:00
Boxy
637a149910 unsafeify World::entities_mut (#4093)
# Objective
make bevy ecs a lil bit less unsound

## Solution
make unsound API unsafe so that there is an unsafe block to blame:

```rust
use bevy_ecs::prelude::*;

#[derive(Debug, Component)]
struct Foo(u8);

fn main() {
    let mut world = World::new();
    let e1 = world.spawn().id();
    let e2 = world.spawn().insert(Foo(2)).id();
    world.entities_mut().meta[0] = world.entities_mut().meta[1].clone();
    let foo = world.entity(e1).get::<Foo>().unwrap();
    // whoo i love having components i dont have
    dbg!(foo);
}
```

This is not _strictly_ speaking UB, however: 
- `Query::get_multiple` cannot work if this is allowed
- bevy_ecs is a pile of unsafe code whose soundness generally depends on the world being in a "correct" state with "no funny business" so it seems best to disallow this
- it is trivial to get bevy to panic inside of functions with safety invariants that have been violated (the entity location is not valid)
- it seems to violate what the safety invariant on `Entities::flush` is trying to ensure
2022-03-30 23:52:45 +00:00