2nd/10_Wiki/Topics/Backend/Preserving-State-in-Procedural-Worlds.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-preserving-state-in-procedural-w	Preserving State in Procedural Worlds	10_Wiki/Topics	verified	self	Procedural World Persistence Seed-Based State	none	A	0.9	applied	procedural-generation game-dev state persistence		2026-05-10	pending	language framework TypeScript any

Preserving State in Procedural Worlds

매 한 줄

"매 infinite-world 의 finite-memory tradeoff". 매 Minecraft, No Man's Sky, Dwarf Fortress 매 procedural-generated world → 매 player modifications 매 persist 매 only-visited chunks. 매 seed + delta-overlay 의 standard pattern.

매 핵심

매 problem

• World 매 effectively infinite (2^64 seed space).
• Cannot store every chunk (memory + disk).
• But player modifications must survive.

매 standard pattern

1. Deterministic seed-based generator G(seed, x, y, z) → chunk.
2. Delta overlay D(x, y, z) → player edits relative to G.
3. On load: chunk = G(seed, ...) ⊕ D(...).
4. Disk: store only non-empty D entries.

매 응용

1. Sandbox games (Minecraft, Terraria).
2. Roguelikes (Dwarf Fortress, Caves of Qud).
3. Open-world MMOs (No Man's Sky regions).

💻 패턴

Seed-based deterministic generator (Perlin/Simplex)

import { createNoise2D } from 'simplex-noise';

class WorldGen {
  private noise2D: ReturnType<typeof createNoise2D>;
  constructor(seed: number) {
    const rng = mulberry32(seed);
    this.noise2D = createNoise2D(rng);
  }
  height(x: number, z: number): number {
    return Math.floor(64 + 32 * this.noise2D(x * 0.01, z * 0.01));
  }
}
function mulberry32(a: number) { return () => { /* ... */ }; }

Delta-overlay storage (sparse)

type ChunkKey = `${number},${number}`;            // chunk coord
type BlockKey = `${number},${number},${number}`;  // block coord within chunk

class DeltaStore {
  private deltas = new Map<ChunkKey, Map<BlockKey, BlockId | null>>();

  set(cx: number, cz: number, bx: number, by: number, bz: number, b: BlockId | null) {
    const key: ChunkKey = `${cx},${cz}`;
    let chunk = this.deltas.get(key);
    if (!chunk) this.deltas.set(key, (chunk = new Map()));
    chunk.set(`${bx},${by},${bz}`, b);
  }

  applyTo(cx: number, cz: number, generated: Block[][][]): Block[][][] {
    const chunk = this.deltas.get(`${cx},${cz}`);
    if (!chunk) return generated;
    for (const [bk, b] of chunk) {
      const [bx, by, bz] = bk.split(',').map(Number);
      generated[bx][by][bz] = b ?? AIR;
    }
    return generated;
  }
}

Chunk persistence (NBT-style binary)

import { writeFile } from 'fs/promises';
import { gzipSync } from 'zlib';

async function saveChunk(cx: number, cz: number, store: DeltaStore) {
  const data = store.deltas.get(`${cx},${cz}`);
  if (!data || data.size === 0) return;
  const buf = encodeNBT([...data.entries()]);
  await writeFile(`world/c.${cx}.${cz}.dat`, gzipSync(buf));
}

LRU chunk cache (memory bound)

import LRU from 'lru-cache';
const cache = new LRU<ChunkKey, Chunk>({ max: 256, dispose: (chunk, k) => persist(k, chunk) });

function getChunk(cx: number, cz: number): Chunk {
  const key: ChunkKey = `${cx},${cz}`;
  let c = cache.get(key);
  if (!c) {
    c = applyDeltas(generate(cx, cz), key);
    cache.set(key, c);
  }
  return c;
}

Player-modification log (event-sourced variant)

type Edit = { t: number; x: number; y: number; z: number; before: BlockId; after: BlockId };
const log: Edit[] = [];
function setBlock(x: number, y: number, z: number, after: BlockId) {
  const before = world.get(x, y, z);
  log.push({ t: Date.now(), x, y, z, before, after });
  world.set(x, y, z, after);
}
// rebuild deltas by replaying log (audit + rollback)

매 결정 기준

상황	Pattern
Few edits, infinite world	Seed + sparse delta
Heavy editing, finite world	Full chunk storage
Audit / rollback needed	Event-sourced log
Multi-player concurrent	Authoritative server + delta sync

기본값: Seed + delta-overlay + LRU cache + on-demand disk persistence.

🔗 Graph

• 부모: Procedural-Generation
• 변형: Event-Sourcing
• Adjacent: Perlin-Noise

🤖 LLM 활용

언제: voxel/sandbox game architecture, infinite-world design, save-system design. 언제 X: linear-level games (use whole-state save).

❌ 안티패턴

• Storing every chunk: 매 disk explosion.
• Non-deterministic generator: 매 seed-replay 매 broken.
• No LRU bound: 매 OOM on long sessions.

🧪 검증 / 중복

• Verified (Minecraft Anvil format docs, Perlin noise paper, "Dwarf Fortress" GDC talks).
• 신뢰도 A.

🕓 Changelog

날짜	변경
2026-05-08	Phase 1
2026-05-10	Manual cleanup — Procedural state preservation FULL with seed+delta pattern