Boids

1"use client"
2 
3import * as React from "react"
4import { useFrame } from "@react-three/fiber"
5import * as THREE from "three"
6 
7import {
8  SceneContainer,
9  type SceneContainerProps,
10} from "@/components/threecn/scene-container"
11import {
12  useShadcnTheme,
13  type ThemeMode,
14} from "@/components/hooks/use-shadcn-theme"
15 
16const BOUND = 4.2
17const PERCEPTION = 1.4
18const SEPARATION = 0.7
19const MAX_SPEED = 2.2
20 
21type Swarm = { pos: Float32Array; vel: Float32Array }
22 
23function seedSwarm(count: number): Swarm {
24  const pos = new Float32Array(count * 3)
25  const vel = new Float32Array(count * 3)
26  for (let i = 0; i < count; i++) {
27    const r = Math.cbrt(Math.random()) * BOUND * 0.7
28    const theta = Math.random() * Math.PI * 2
29    const phi = Math.acos(2 * Math.random() - 1)
30    pos[i * 3] = r * Math.sin(phi) * Math.cos(theta)
31    pos[i * 3 + 1] = r * Math.sin(phi) * Math.sin(theta)
32    pos[i * 3 + 2] = r * Math.cos(phi)
33    vel[i * 3] = (Math.random() - 0.5) * 2
34    vel[i * 3 + 1] = (Math.random() - 0.5) * 2
35    vel[i * 3 + 2] = (Math.random() - 0.5) * 2
36  }
37  return { pos, vel }
38}
39 
40function Flock({
41  count,
42  speed,
43  theme,
44}: {
45  count: number
46  speed: number
47  theme: ThemeMode
48}) {
49  const { primaryColor, accentColor } = useShadcnTheme(theme)
50  const meshRef = React.useRef<THREE.InstancedMesh>(null)
51  const swarmRef = React.useRef<Swarm | null>(null)
52 
53  // The swarm is mutated every frame, so it lives in a ref (never read during
54  // render). Seed it whenever the agent count changes.
55  React.useLayoutEffect(() => {
56    swarmRef.current = seedSwarm(count)
57  }, [count])
58 
59  const dummy = React.useMemo(() => new THREE.Object3D(), [])
60  const tmpColor = React.useMemo(() => new THREE.Color(), [])
61  const up = React.useMemo(() => new THREE.Vector3(0, 1, 0), [])
62  const dir = React.useMemo(() => new THREE.Vector3(), [])
63 
64  useFrame((_, delta) => {
65    const mesh = meshRef.current
66    const swarm = swarmRef.current
67    if (!mesh || !swarm) return
68    const dt = Math.min(delta, 0.05) * speed
69    const { pos, vel } = swarm
70 
71    for (let i = 0; i < count; i++) {
72      const io = i * 3
73      const px = pos[io]
74      const py = pos[io + 1]
75      const pz = pos[io + 2]
76 
77      let ax = 0
78      let ay = 0
79      let az = 0 // alignment
80      let cx = 0
81      let cy = 0
82      let cz = 0 // cohesion
83      let sx = 0
84      let sy = 0
85      let sz = 0 // separation
86      let n = 0
87 
88      for (let j = 0; j < count; j++) {
89        if (j === i) continue
90        const jo = j * 3
91// … truncated