From f4079d173a041f44e7e8d9b75f3c290179611c7b Mon Sep 17 00:00:00 2001
From: Zynh Ludwig <Zynh0722@gmail.com>
Date: Tue, 3 Sep 2024 15:14:21 -0700
Subject: [PATCH] cache local boids

---
 src/main.rs | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/src/main.rs b/src/main.rs
index ef34552..624044c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,7 +3,7 @@
 mod boid_mesh;
 mod boundary;
 
-use bevy::{color::palettes::tailwind, prelude::*, sprite::MaterialMesh2dBundle};
+use bevy::{color::palettes::tailwind, prelude::*, reflect::List, sprite::MaterialMesh2dBundle};
 use boid_mesh::BoidMesh;
 use rand::{Rng, SeedableRng};
 
@@ -54,6 +54,32 @@ struct BoidBundle {
     cache: BoidAccelerationBundle,
 }
 
+#[derive(Component, Default)]
+struct LocalCache(Vec<Entity>);
+
+fn is_local(a: Vec3, b: Vec3) -> bool {
+    const LOCAL_DISTANCE: f32 = 100.;
+
+    a.distance(b) < LOCAL_DISTANCE
+}
+
+fn build_local_cache(
+    mut boids_with_cache: Query<(Entity, &Transform, &mut LocalCache), With<Boid>>,
+    other_boids: Query<(Entity, &Transform), With<Boid>>,
+) {
+    boids_with_cache
+        .par_iter_mut()
+        .for_each(|(id, transform, mut local_cache)| {
+            local_cache.0.clear();
+
+            for (other_id, other_transform) in other_boids.iter() {
+                if id != other_id && is_local(transform.translation, other_transform.translation) {
+                    local_cache.0.push(other_id);
+                }
+            }
+        });
+}
+
 fn seperation(mut boids: Query<(Entity, &Transform, &mut SeperationAcceleration), With<Boid>>) {}
 
 fn cohesion(mut boids: Query<(Entity, &Transform, &mut SeperationAcceleration), With<Boid>>) {}