herd / files / src / game / GameLoop.ts

GameLoop.ts

1	const FIXED_STEP_MS = 16 // ~60 Hz physics
2
3	export class GameLoop {
4	private rafId = 0
5	private lastTime = 0
6	private accumulator = 0
7	private running = false
8	private onUpdate: (dt: number) => void
9	private onRender: (alpha: number) => void
10
11	constructor(onUpdate: (dt: number) => void, onRender: (alpha: number) => void) {
12	this.onUpdate = onUpdate
13	this.onRender = onRender
14	}
15
16	start() {
17	if (this.running) return
18	this.running = true
19	this.lastTime = performance.now()
20	this.rafId = requestAnimationFrame(this.tick)
21	}
22
23	stop() {
24	this.running = false
25	cancelAnimationFrame(this.rafId)
26	}
27
28	private tick = (now: number) => {
29	if (!this.running) return
30	this.rafId = requestAnimationFrame(this.tick)
31
32	const elapsed = Math.min(now - this.lastTime, 200) // cap at 200ms to avoid spiral of death
33	this.lastTime = now
34	this.accumulator += elapsed
35
36	while (this.accumulator >= FIXED_STEP_MS) {
37	this.onUpdate(FIXED_STEP_MS / 1000) // pass seconds
38	this.accumulator -= FIXED_STEP_MS
39	}
40
41	this.onRender(this.accumulator / FIXED_STEP_MS)
42	}
43	}