2nd/10_Wiki/Topics/Architecture/Beat_Saber.md

id, title, category, status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, verification_status, tags, raw_sources, last_reinforced, github_commit, tech_stack

id	title	category	status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	verification_status	tags	raw_sources	last_reinforced	github_commit	tech_stack
wiki-2026-0508-beat-saber	Beat Saber	10_Wiki/Topics	verified	self	Beat Saber VR Rhythm Game	none	A	0.85	applied	vr game-architecture rhythm-game unity ecs		2026-05-10	pending	language framework csharp unity,unity-dots,openxr

Beat Saber

매 한 줄

"매 VR rhythm game 의 architecture 의 reference — 90Hz minimum framerate · sub-20ms motion-to-photon · ECS-style note pool". 2018 Beat Games (Meta acq 2019) release, 2026 의 Quest 3/Vision Pro 의 cross-platform mainstream, "framerate 의 holy 의 above 의 nothing" 의 architecture 의 lesson.

매 핵심

매 architecture 제약

• Framerate floor: 90 fps (Quest 2) · 120 fps (Quest 3 · Vision Pro).
• Motion-to-photon: < 20 ms.
• GC 의 hostile: 매 frame 의 spike 의 nausea 의 cause → object pool · Burst · Job System.
• Determinism: scoring 의 reproducible — 매 input · note 의 fixed seed.

매 component

• Beatmap loader: .dat JSON parse → preallocated note buffer.
• Note spawner: 매 future 6 sec 의 lookahead, pool 에서 의 pull.
• Saber controller: hand pose tracking + velocity smoothing.
• Cut detector: plane intersection · direction match · score.
• Audio sync: NJS (Note Jump Speed) + offset 의 calibrate.

매 응용

1. 매 fitness app (Supernatural, FitXR) 의 rhythm pattern 의 inherit.
2. Trainer/simulator (medical · drill) 의 timing-critical UX.
3. Education app (language drill · typing tutor) 의 VR variant.

💻 패턴

Unity DOTS: note spawn 의 zero-alloc

[BurstCompile]
public partial struct NoteSpawnSystem : ISystem
{
    public void OnUpdate(ref SystemState state)
    {
        var beatmap = SystemAPI.GetSingleton<BeatmapBuffer>();
        var time = SystemAPI.Time.ElapsedTime;
        var ecb = new EntityCommandBuffer(Allocator.Temp);

        for (int i = beatmap.NextIndex; i < beatmap.Notes.Length; i++)
        {
            var n = beatmap.Notes[i];
            if (n.Time - time > LookaheadSeconds) break;

            var e = ecb.Instantiate(beatmap.NotePrefab);
            ecb.SetComponent(e, new Translation { Value = n.SpawnPosition });
            ecb.SetComponent(e, new NoteData { CutDirection = n.Direction, HitTime = n.Time });
            beatmap.NextIndex = i + 1;
        }

        ecb.Playback(state.EntityManager);
    }
}

Saber-cut detector (plane intersection)

public bool TryCut(Vector3 saberTip, Vector3 saberBase, Vector3 saberVelocity, NoteData note,
                  out CutResult result)
{
    var plane = new Plane(saberVelocity.normalized, saberBase);
    if (!plane.Raycast(new Ray(note.Position, note.Forward), out float enter)) {
        result = default; return false;
    }

    float speed     = saberVelocity.magnitude;
    float angle     = Vector3.Angle(saberVelocity, note.RequiredCutDirection);
    float accuracy  = 1f - Mathf.Clamp01(angle / 60f);

    result = new CutResult {
        Score = Mathf.RoundToInt(speed * accuracy * 115f),
        IsValid = speed > 2f && angle < 60f,
    };
    return result.IsValid;
}

Audio-visual sync (NJS-based)

// Note 의 spawn position 의 calc
float jumpDist = njs * (60f / bpm) * halfJumpDuration * 2f;
Vector3 spawnPos = playerPosition + Vector3.forward * jumpDist;

// Note 의 frame 마다 의 lerp
float t = (Time.timeAsDouble - spawnTime) / (hitTime - spawnTime);
note.transform.position = Vector3.Lerp(spawnPos, hitPos, (float)t);

Object pool (zero-GC frame)

public class NotePool
{
    readonly Stack<Note> pool = new(256);
    readonly Note prefab;

    public Note Get() => pool.Count > 0 ? pool.Pop() : Object.Instantiate(prefab);
    public void Return(Note n) {
        n.gameObject.SetActive(false);
        pool.Push(n);
    }
}

OpenXR foveated rendering hint (Quest 3)

var feature = OpenXRSettings.Instance.GetFeature<FoveationFeature>();
feature.foveatedRenderingLevel = FoveatedRenderingLevel.High;
feature.useDynamicFoveatedRendering = true; // eye-tracked on Quest 3

매 결정 기준

상황	Approach
< 100 active note · prototype	MonoBehaviour + pool
> 200 active note · production	DOTS/ECS + Burst
Cross-platform (PCVR + Quest)	Unity URP + multi-quality preset
Modding support	Open beatmap format (.dat) + PluginLoader
매 90fps 미달 의 perf budget	Foveation · LOD · GPU instancing

기본값: Unity DOTS + URP + OpenXR — 매 Quest 3 의 baseline 의 fit.

🔗 Graph

• 응용: bitECS와_SharedArrayBuffer의_실제_코드_통합
• Adjacent: Object Pool

🤖 LLM 활용

언제: beatmap 의 procedural generation, cut-direction pattern 의 difficulty curve 의 tune, NJS · offset 의 starter value 의 suggest. 언제 X: 매 hand-crafted choreography (top mapper 의 art form) — LLM 의 generate 의 bland.

❌ 안티패턴

• GC 의 frame 의 allocate: 매 90fps 의 break → motion sickness.
• Animation curve 의 audio sync: dt 의 drift → pop. NJS-based linear lerp 의 use.
• Saber 의 trigger collider: physics step 의 sub-frame miss — manual raycast/plane 의 use.
• Per-note GameObject Instantiate: pool 의 mandatory.

🧪 검증 / 중복

• Verified (Beat Games postmortem GDC 2019, Unity DOTS 1.3 docs, OpenXR 1.1 spec, BSMG modding wiki).
• 신뢰도 A-.

🕓 Changelog

날짜	변경
2026-05-08	Phase 1
2026-05-10	Manual cleanup — VR architecture constraints + DOTS spawner + cut detector