use bounding boxes to optimize collision detection

src/projectile.js

@@ -1,10 +1,12 @@
 import { Vector2 } from 'three'
 import SAT from 'sat'
 import SATX from './satx.js'
+import Entity from './entity.js'
 
 export default class Projectile {
   id = crypto.randomUUID()
   after = null // TODO: hide from reports but keep public
+  bbox = new Float32Array(4)
   height = 50
   memory = {} // TODO: hide from reports but keep public
   onCollide = null // TODO: hide from reports but keep public
@@ -36,6 +38,7 @@ export default class Projectile {
 
   checkCollisions(collider) {
     (this.game?.entities ?? []).filter((e) => e.id != this.id).forEach((e) => {
+      if (this.game == null) { return }
       if (e.id == this.owner?.id) { return }
 
       if (SATX.collideObject(collider, e.collider())) {
@@ -54,10 +57,18 @@ export default class Projectile {
 
   update() {
     this.#move()
+    this.#calculateBbox()
     if (this.onCollide != null) { this.checkCollisions(this.collider()) }
     this.#checkIfArrived()
   }
 
+  #calculateBbox() {
+    this.bbox[0] = this.position.y + this.radius
+    this.bbox[1] = this.position.x + this.radius
+    this.bbox[2] = this.position.y - this.radius
+    this.bbox[3] = this.position.x - this.radius
+  }
+
   #checkIfArrived() {
     if (this.destination == null) { return }
     if (!this.position.equals(this.destination)) { return }
@@ -82,7 +93,8 @@ export default class Projectile {
       this.position.add(step)
     }
 
-    const tunnel = SATX.entityTunnel(prevPos.x, prevPos.y, this.position.x, this.position.y, this.radius)
+    // TODO: decouple from entity's tunnel collider
+    const tunnel = Entity.tunnelCollider(prevPos.x, prevPos.y, this.position.x, this.position.y, this.radius)
     if (this.onCollide != null) { this.checkCollisions(tunnel) }
   }
 }