robert/another-boids-in-rust
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Convert flocking systems to use Avian2d

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This commit is contained in:
Robert Garrett
2025-12-24 16:02:46 -06:00
parent e252e3385c
commit 1846b7065e
1 changed files with 55 additions and 49 deletions
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104
src/birdoids/mod.rs
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@@ -2,9 +2,6 @@ pub mod physics;
use avian2d::prelude::*;
use bevy::prelude::*;
use bevy_spatial::{
AutomaticUpdate, SpatialAccess, SpatialStructure, TransformMode, kdtree::KDTree2,
};
use crate::birdoids::physics::{Force, Velocity, apply_velocity};
use bevy_inspector_egui::{InspectorOptions, prelude::ReflectInspectorOptions};
@@ -15,29 +12,23 @@ pub struct BoidsPlugin;
impl Plugin for BoidsPlugin {
fn build(&self, app: &mut App) {
app.add_plugins(
AutomaticUpdate::<TrackedByKdTree>::new()
// .with_frequency(Duration::from_secs_f32(0.3))
.with_transform(TransformMode::GlobalTransform)
.with_spatial_ds(SpatialStructure::KDTree2),
)
.insert_resource(ClearColor(BACKGROUND_COLOR))
.insert_resource(FlockingParameters::new())
.register_type::<FlockingParameters>()
.insert_resource(MiscParams::new())
.register_type::<MiscParams>()
.add_systems(Startup, (spawn_camera, spawn_boids))
.add_systems(
FixedUpdate,
(
apply_velocity,
turn_if_edge,
cohesion,
separation,
alignment,
speed_controller,
),
);
app.insert_resource(ClearColor(BACKGROUND_COLOR))
.insert_resource(FlockingParameters::new())
.register_type::<FlockingParameters>()
.insert_resource(MiscParams::new())
.register_type::<MiscParams>()
.add_systems(Startup, (spawn_camera, spawn_boids))
.add_systems(
FixedUpdate,
(
apply_velocity,
turn_if_edge,
cohesion,
separation,
alignment,
speed_controller,
),
);
}
}
@@ -82,12 +73,9 @@ impl MiscParams {
}
#[derive(Component)]
#[require(Velocity, Force, TrackedByKdTree)]
#[require(Velocity, Force)]
pub(crate) struct Boid;
#[derive(Component, Default)]
pub struct TrackedByKdTree;
fn spawn_camera(mut commands: Commands) {
commands.spawn(Camera2d);
}
@@ -153,7 +141,9 @@ fn turn_if_edge(
}
fn cohesion(
spatial_tree: Res<KDTree2<TrackedByKdTree>>,
spatial: SpatialQuery,
// TODO: Ensure this is logically sound. I think it will fail the "disjoint queries" requirement.
boid_locations: Query<&Transform, With<Boid>>,
mut boids: Query<(Entity, &Transform, &mut Force), With<Boid>>,
props: Res<FlockingParameters>,
) {
@@ -163,14 +153,23 @@ fn cohesion(
// find vector from boid to flock CoM
// apply force
for (this_entt, transform, mut force) in &mut boids {
let (len, sum) = spatial_tree
.within_distance(transform.translation.xy(), props.view_range)
let (len, sum) = spatial
.shape_intersections(
&Collider::circle(props.view_range),
transform.translation.xy(),
0.0,
&SpatialQueryFilter::default(),
)
.iter()
.filter_map(|(pos, entt)| {
.filter_map(|&entt| {
// extract neighbor's position
// Skip self-comparison. A boid should not try to separate from itself.
let entt = entt
.expect("within_distance gave me an entity... with no entity ID... somehow");
if this_entt == entt { None } else { Some(pos) }
if this_entt == entt {
None
} else {
let tsfm = boid_locations.get(entt).unwrap();
Some(tsfm.translation.xy())
}
})
.enumerate()
.fold((0, Vec2::ZERO), |(_len, com), (idx, pos)| (idx, com + pos));
@@ -190,7 +189,8 @@ fn cohesion(
}
fn separation(
spatial_tree: Res<KDTree2<TrackedByKdTree>>,
spatial: SpatialQuery,
boid_locations: Query<&Transform, With<Boid>>,
mut boids: Query<(Entity, &Transform, &mut Force), With<Boid>>,
props: Res<FlockingParameters>,
) {
@@ -199,16 +199,20 @@ fn separation(
// sum force from neighbors
// apply force
for (this_entt, tsfm, mut force) in &mut boids {
let impulse = spatial_tree
.within_distance(tsfm.translation.xy(), props.view_range / 4.0)
let impulse = spatial
.shape_intersections(
&Collider::circle(props.view_range),
tsfm.translation.xy(),
0.0,
&SpatialQueryFilter::default(),
)
.iter()
.filter_map(|(pos, entt)| {
.filter_map(|&entt| {
// Skip self-comparison. A boid should not try to separate from itself.
let entt = entt
.expect("within_distance gave me an entity... with no entity ID... somehow");
if this_entt == entt {
None
} else {
let pos = boid_locations.get(entt).unwrap().translation.xy();
Some(pos.extend(0.0))
}
})
@@ -223,7 +227,7 @@ fn separation(
}
fn alignment(
spatial_tree: Res<KDTree2<TrackedByKdTree>>,
spatial: SpatialQuery,
mut boids: Query<(Entity, &Transform, &mut Force), With<Boid>>,
boid_velocities: Query<&Velocity, With<Boid>>,
props: Res<FlockingParameters>,
@@ -236,14 +240,16 @@ fn alignment(
// apply steering force
for (this_entt, transform, mut force) in &mut boids {
let neighbors = spatial_tree.within_distance(transform.translation.xy(), props.view_range);
let neighbors = spatial.shape_intersections(
&Collider::circle(props.view_range),
transform.translation.xy(),
0.0,
&SpatialQueryFilter::default(),
);
// averaging divides by length. Guard against an empty set of neighbors
let (len, sum) = neighbors
.iter()
// Extract the velocities by `get()`ing from another query param.
.filter_map(|(_pos, maybe_entt)| {
let entt = maybe_entt
.expect("Neighbor boid has no Entity ID. I don't know what this means");
.filter_map(|&entt| {
if this_entt == entt {
None
} else {