# Objective
Update the `calculate_bounds` system to update `Aabb`s
for entities who've either:
- gotten a new mesh
- had their mesh mutated
Fixes https://github.com/bevyengine/bevy/issues/4294.
## Solution
There are two commits here to address the two issues above:
### Commit 1
**This Commit**
Updates the `calculate_bounds` system to operate not only on entities
without `Aabb`s but also on entities whose `Handle<Mesh>` has changed.
**Why?**
So if an entity gets a new mesh, its associated `Aabb` is properly
recalculated.
**Questions**
- This type is getting pretty gnarly - should I extract some types?
- This system is public - should I add some quick docs while I'm here?
### Commit 2
**This Commit**
Updates `calculate_bounds` to update `Aabb`s of entities whose meshes
have been directly mutated.
**Why?**
So if an entity's mesh gets updated, its associated `Aabb` is properly
recalculated.
**Questions**
- I think we should be using `ahash`. Do we want to do that with a
direct `hashbrown` dependency or an `ahash` dependency that we
configure the `HashMap` with?
- There is an edge case of duplicates with `Vec<Entity>` in the
`HashMap`. If an entity gets its mesh handle changed and changed back
again it'll be added to the list twice. Do we want to use a `HashSet`
to avoid that? Or do a check in the list first (assuming iterating
over the `Vec` is faster and this edge case is rare)?
- There is an edge case where, if an entity gets a new mesh handle and
then its old mesh is updated, we'll update the entity's `Aabb` to the
new geometry of the _old_ mesh. Do we want to remove items from the
`Local<HashMap>` when handles change? Does the `Changed` event give us
the old mesh handle? If not we might need to have a
`HashMap<Entity, Handle<Mesh>>` or something so we can unlink entities
from mesh handles when the handle changes.
- I did the `zip()` with the two `HashMap` gets assuming those would
be faster than calculating the Aabb of the mesh (otherwise we could do
`meshes.get(mesh_handle).and_then(Mesh::compute_aabb).zip(entity_mesh_map...)`
or something). Is that assumption way off?
## Testing
I originally tried testing this with `bevy_mod_raycast` as mentioned in the
original issue but it seemed to work (maybe they are currently manually
updating the Aabbs?). I then tried doing it in 2D but it looks like
`Handle<Mesh>` is just for 3D. So I took [this example](https://github.com/bevyengine/bevy/blob/main/examples/3d/pbr.rs)
and added some systems to mutate/assign meshes:
<details>
<summary>Test Script</summary>
```rust
use bevy::prelude::*;
use bevy::render:📷:ScalingMode;
use bevy::render::primitives::Aabb;
/// Make sure we only mutate one mesh once.
#[derive(Eq, PartialEq, Clone, Debug, Default)]
struct MutateMeshState(bool);
/// Let's have a few global meshes that we can cycle between.
/// This way we can be assigned a new mesh, mutate the old one, and then get the old one assigned.
#[derive(Eq, PartialEq, Clone, Debug, Default)]
struct Meshes(Vec<Handle<Mesh>>);
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.init_resource::<MutateMeshState>()
.init_resource::<Meshes>()
.add_startup_system(setup)
.add_system(assign_new_mesh)
.add_system(show_aabbs.after(assign_new_mesh))
.add_system(mutate_meshes.after(show_aabbs))
.run();
}
fn setup(
mut commands: Commands,
mut meshes: ResMut<Assets<Mesh>>,
mut global_meshes: ResMut<Meshes>,
mut materials: ResMut<Assets<StandardMaterial>>,
) {
let m1 = meshes.add(Mesh::from(shape::Icosphere::default()));
let m2 = meshes.add(Mesh::from(shape::Icosphere {
radius: 0.90,
..Default::default()
}));
let m3 = meshes.add(Mesh::from(shape::Icosphere {
radius: 0.80,
..Default::default()
}));
global_meshes.0.push(m1.clone());
global_meshes.0.push(m2);
global_meshes.0.push(m3);
// add entities to the world
// sphere
commands.spawn_bundle(PbrBundle {
mesh: m1,
material: materials.add(StandardMaterial {
base_color: Color::hex("ffd891").unwrap(),
..default()
}),
..default()
});
// new 3d camera
commands.spawn_bundle(Camera3dBundle {
projection: OrthographicProjection {
scale: 3.0,
scaling_mode: ScalingMode::FixedVertical(1.0),
..default()
}
.into(),
..default()
});
// old 3d camera
// commands.spawn_bundle(OrthographicCameraBundle {
// transform: Transform::from_xyz(0.0, 0.0, 8.0).looking_at(Vec3::default(), Vec3::Y),
// orthographic_projection: OrthographicProjection {
// scale: 0.01,
// ..default()
// },
// ..OrthographicCameraBundle::new_3d()
// });
}
fn show_aabbs(query: Query<(Entity, &Handle<Mesh>, &Aabb)>) {
for thing in query.iter() {
println!("{thing:?}");
}
}
/// For testing the second part - mutating a mesh.
///
/// Without the fix we should see this mutate an old mesh and it affects the new mesh that the
/// entity currently has.
/// With the fix, the mutation doesn't affect anything until the entity is reassigned the old mesh.
fn mutate_meshes(
mut meshes: ResMut<Assets<Mesh>>,
time: Res<Time>,
global_meshes: Res<Meshes>,
mut mutate_mesh_state: ResMut<MutateMeshState>,
) {
let mutated = mutate_mesh_state.0;
if time.seconds_since_startup() > 4.5 && !mutated {
println!("Mutating {:?}", global_meshes.0[0]);
let m = meshes.get_mut(&global_meshes.0[0]).unwrap();
let mut p = m.attribute(Mesh::ATTRIBUTE_POSITION).unwrap().clone();
use bevy::render::mesh::VertexAttributeValues;
match &mut p {
VertexAttributeValues::Float32x3(v) => {
v[0] = [10.0, 10.0, 10.0];
}
_ => unreachable!(),
}
m.insert_attribute(Mesh::ATTRIBUTE_POSITION, p);
mutate_mesh_state.0 = true;
}
}
/// For testing the first part - assigning a new handle.
fn assign_new_mesh(
mut query: Query<&mut Handle<Mesh>, With<Aabb>>,
time: Res<Time>,
global_meshes: Res<Meshes>,
) {
let s = time.seconds_since_startup() as usize;
let idx = s % global_meshes.0.len();
for mut handle in query.iter_mut() {
*handle = global_meshes.0[idx].clone_weak();
}
}
```
</details>
## Changelog
### Fixed
Entity `Aabb`s not updating when meshes are mutated or re-assigned.
c2b332f98a