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Author SHA1 Message Date
Kristoffer Søholm
2d1b4939d2
Synchronize removed components with the render world (#15582)
# Objective

Fixes #15560
Fixes (most of) #15570

Currently a lot of examples (and presumably some user code) depend on
toggling certain render features by adding/removing a single component
to an entity, e.g. `SpotLight` to toggle a light. Because of the
retained render world this no longer works: Extract will add any new
components, but when it is removed the entity persists unchanged in the
render world.

## Solution

Add `SyncComponentPlugin<C: Component>` that registers
`SyncToRenderWorld` as a required component for `C`, and adds a
component hook that will clear all components from the render world
entity when `C` is removed. We add this plugin to
`ExtractComponentPlugin` which fixes most instances of the problem. For
custom extraction logic we can manually add `SyncComponentPlugin` for
that component.

We also rename `WorldSyncPlugin` to `SyncWorldPlugin` so we start a
naming convention like all the `Extract` plugins.

In this PR I also fixed a bunch of breakage related to the retained
render world, stemming from old code that assumed that `Entity` would be
the same in both worlds.

I found that using the `RenderEntity` wrapper instead of `Entity` in
data structures when referring to render world entities makes intent
much clearer, so I propose we make this an official pattern.

## Testing

Run examples like

```
cargo run --features pbr_multi_layer_material_textures --example clearcoat
cargo run --example volumetric_fog
```

and see that they work, and that toggles work correctly. But really we
should test every single example, as we might not even have caught all
the breakage yet.

---

## Migration Guide

The retained render world notes should be updated to explain this edge
case and `SyncComponentPlugin`

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Trashtalk217 <trashtalk217@gmail.com>
2024-10-08 22:23:17 +00:00
Christian Hughes
584d14808a
Allow World::entity family of functions to take multiple entities and get multiple references back (#15614)
# Objective

Following the pattern established in #15593, we can reduce the API
surface of `World` by providing a single function to grab both a
singular entity reference, or multiple entity references.

## Solution

The following functions can now also take multiple entity IDs and will
return multiple entity references back:
- `World::entity`
- `World::get_entity`
- `World::entity_mut`
- `World::get_entity_mut`
- `DeferredWorld::entity_mut`
- `DeferredWorld::get_entity_mut`

If you pass in X, you receive Y:
- give a single `Entity`, receive a single `EntityRef`/`EntityWorldMut`
(matches current behavior)
- give a `[Entity; N]`/`&[Entity; N]` (array), receive an equally-sized
`[EntityRef; N]`/`[EntityMut; N]`
- give a `&[Entity]` (slice), receive a
`Vec<EntityRef>`/`Vec<EntityMut>`
- give a `&EntityHashSet`, receive a
`EntityHashMap<EntityRef>`/`EntityHashMap<EntityMut>`

Note that `EntityWorldMut` is only returned in the single-entity case,
because having multiple at the same time would lead to UB. Also,
`DeferredWorld` receives an `EntityMut` in the single-entity case
because it does not allow structural access.

## Testing

- Added doc-tests on `World::entity`, `World::entity_mut`, and
`DeferredWorld::entity_mut`
- Added tests for aliased mutability and entity existence

---

## Showcase

<details>
  <summary>Click to view showcase</summary>

The APIs for fetching `EntityRef`s and `EntityMut`s from the `World`
have been unified.

```rust
// This code will be referred to by subsequent code blocks.
let world = World::new();
let e1 = world.spawn_empty().id();
let e2 = world.spawn_empty().id();
let e3 = world.spawn_empty().id();
```

Querying for a single entity remains mostly the same:

```rust
// 0.14
let eref: EntityRef = world.entity(e1);
let emut: EntityWorldMut = world.entity_mut(e1);
let eref: Option<EntityRef> = world.get_entity(e1);
let emut: Option<EntityWorldMut> = world.get_entity_mut(e1);

// 0.15
let eref: EntityRef = world.entity(e1);
let emut: EntityWorldMut = world.entity_mut(e1);
let eref: Result<EntityRef, Entity> = world.get_entity(e1);
let emut: Result<EntityWorldMut, Entity> = world.get_entity_mut(e1);
```

Querying for multiple entities with an array has changed:

```rust
// 0.14
let erefs: [EntityRef; 2] = world.many_entities([e1, e2]);
let emuts: [EntityMut; 2] = world.many_entities_mut([e1, e2]);
let erefs: Result<[EntityRef; 2], Entity> = world.get_many_entities([e1, e2]);
let emuts: Result<[EntityMut; 2], QueryEntityError> = world.get_many_entities_mut([e1, e2]);

// 0.15
let erefs: [EntityRef; 2] = world.entity([e1, e2]);
let emuts: [EntityMut; 2] = world.entity_mut([e1, e2]);
let erefs: Result<[EntityRef; 2], Entity> = world.get_entity([e1, e2]);
let emuts: Result<[EntityMut; 2], EntityFetchError> = world.get_entity_mut([e1, e2]);
```

Querying for multiple entities with a slice has changed:

```rust
let ids = vec![e1, e2, e3]);

// 0.14
let erefs: Result<Vec<EntityRef>, Entity> = world.get_many_entities_dynamic(&ids[..]);
let emuts: Result<Vec<EntityMut>, QueryEntityError> = world.get_many_entities_dynamic_mut(&ids[..]);

// 0.15
let erefs: Result<Vec<EntityRef>, Entity> = world.get_entity(&ids[..]);
let emuts: Result<Vec<EntityMut>, EntityFetchError> = world.get_entity_mut(&ids[..]);
let erefs: Vec<EntityRef> = world.entity(&ids[..]); // Newly possible!
let emuts: Vec<EntityMut> = world.entity_mut(&ids[..]); // Newly possible!
```

Querying for multiple entities with an `EntityHashSet` has changed:

```rust
let set = EntityHashSet::from_iter([e1, e2, e3]);

// 0.14
let emuts: Result<Vec<EntityMut>, QueryEntityError> = world.get_many_entities_from_set_mut(&set);

// 0.15
let emuts: Result<EntityHashMap<EntityMut>, EntityFetchError> = world.get_entity_mut(&set);
let erefs: Result<EntityHashMap<EntityRef>, EntityFetchError> = world.get_entity(&set); // Newly possible!
let emuts: EntityHashMap<EntityMut> = world.entity_mut(&set); // Newly possible!
let erefs: EntityHashMap<EntityRef> = world.entity(&set); // Newly possible!
```

</details>

## Migration Guide

- `World::get_entity` now returns `Result<_, Entity>` instead of
`Option<_>`.
- Use `world.get_entity(..).ok()` to return to the previous behavior.
- `World::get_entity_mut` and `DeferredWorld::get_entity_mut` now return
`Result<_, EntityFetchError>` instead of `Option<_>`.
- Use `world.get_entity_mut(..).ok()` to return to the previous
behavior.
- Type inference for `World::entity`, `World::entity_mut`,
`World::get_entity`, `World::get_entity_mut`,
`DeferredWorld::entity_mut`, and `DeferredWorld::get_entity_mut` has
changed, and might now require the input argument's type to be
explicitly written when inside closures.
- The following functions have been deprecated, and should be replaced
as such:
    - `World::many_entities` -> `World::entity::<[Entity; N]>`
    - `World::many_entities_mut` -> `World::entity_mut::<[Entity; N]>`
    - `World::get_many_entities` -> `World::get_entity::<[Entity; N]>`
- `World::get_many_entities_dynamic` -> `World::get_entity::<&[Entity]>`
- `World::get_many_entities_mut` -> `World::get_entity_mut::<[Entity;
N]>`
- The equivalent return type has changed from `Result<_,
QueryEntityError>` to `Result<_, EntityFetchError>`
- `World::get_many_entities_dynamic_mut` ->
`World::get_entity_mut::<&[Entity]>1
- The equivalent return type has changed from `Result<_,
QueryEntityError>` to `Result<_, EntityFetchError>`
- `World::get_many_entities_from_set_mut` ->
`World::get_entity_mut::<&EntityHashSet>`
- The equivalent return type has changed from `Result<Vec<EntityMut>,
QueryEntityError>` to `Result<EntityHashMap<EntityMut>,
EntityFetchError>`. If necessary, you can still convert the
`EntityHashMap` into a `Vec`.
2024-10-07 15:21:40 +00:00
Trashtalk217
56f8e526dd
The Cooler 'Retain Rendering World' (#15320)
- Adopted from #14449
- Still fixes #12144.

## Migration Guide

The retained render world is a complex change: migrating might take one
of a few different forms depending on the patterns you're using.

For every example, we specify in which world the code is run. Most of
the changes affect render world code, so for the average Bevy user who's
using Bevy's high-level rendering APIs, these changes are unlikely to
affect your code.

### Spawning entities in the render world

Previously, if you spawned an entity with `world.spawn(...)`,
`commands.spawn(...)` or some other method in the rendering world, it
would be despawned at the end of each frame. In 0.15, this is no longer
the case and so your old code could leak entities. This can be mitigated
by either re-architecting your code to no longer continuously spawn
entities (like you're used to in the main world), or by adding the
`bevy_render::world_sync::TemporaryRenderEntity` component to the entity
you're spawning. Entities tagged with `TemporaryRenderEntity` will be
removed at the end of each frame (like before).

### Extract components with `ExtractComponentPlugin`

```
// main world
app.add_plugins(ExtractComponentPlugin::<ComponentToExtract>::default());
```

`ExtractComponentPlugin` has been changed to only work with synced
entities. Entities are automatically synced if `ComponentToExtract` is
added to them. However, entities are not "unsynced" if any given
`ComponentToExtract` is removed, because an entity may have multiple
components to extract. This would cause the other components to no
longer get extracted because the entity is not synced.

So be careful when only removing extracted components from entities in
the render world, because it might leave an entity behind in the render
world. The solution here is to avoid only removing extracted components
and instead despawn the entire entity.

### Manual extraction using `Extract<Query<(Entity, ...)>>`

```rust
// in render world, inspired by bevy_pbr/src/cluster/mod.rs
pub fn extract_clusters(
    mut commands: Commands,
    views: Extract<Query<(Entity, &Clusters, &Camera)>>,
) {
    for (entity, clusters, camera) in &views {
        // some code
        commands.get_or_spawn(entity).insert(...);
    }
}
```
One of the primary consequences of the retained rendering world is that
there's no longer a one-to-one mapping from entity IDs in the main world
to entity IDs in the render world. Unlike in Bevy 0.14, Entity 42 in the
main world doesn't necessarily map to entity 42 in the render world.

Previous code which called `get_or_spawn(main_world_entity)` in the
render world (`Extract<Query<(Entity, ...)>>` returns main world
entities). Instead, you should use `&RenderEntity` and
`render_entity.id()` to get the correct entity in the render world. Note
that this entity does need to be synced first in order to have a
`RenderEntity`.

When performing manual abstraction, this won't happen automatically
(like with `ExtractComponentPlugin`) so add a `SyncToRenderWorld` marker
component to the entities you want to extract.

This results in the following code:
```rust
// in render world, inspired by bevy_pbr/src/cluster/mod.rs
pub fn extract_clusters(
    mut commands: Commands,
    views: Extract<Query<(&RenderEntity, &Clusters, &Camera)>>,
) {
    for (render_entity, clusters, camera) in &views {
        // some code
        commands.get_or_spawn(render_entity.id()).insert(...);
    }
}

// in main world, when spawning
world.spawn(Clusters::default(), Camera::default(), SyncToRenderWorld)
```

### Looking up `Entity` ids in the render world

As previously stated, there's now no correspondence between main world
and render world `Entity` identifiers.

Querying for `Entity` in the render world will return the `Entity` id in
the render world: query for `MainEntity` (and use its `id()` method) to
get the corresponding entity in the main world.

This is also a good way to tell the difference between synced and
unsynced entities in the render world, because unsynced entities won't
have a `MainEntity` component.

---------

Co-authored-by: re0312 <re0312@outlook.com>
Co-authored-by: re0312 <45868716+re0312@users.noreply.github.com>
Co-authored-by: Periwink <charlesbour@gmail.com>
Co-authored-by: Anselmo Sampietro <ans.samp@gmail.com>
Co-authored-by: Emerson Coskey <56370779+ecoskey@users.noreply.github.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Christian Hughes <9044780+ItsDoot@users.noreply.github.com>
2024-09-30 18:51:43 +00:00