# LANE C — INTERIORS · progress (PROCITY-C)

*Status: **v1 complete & verified**. Standalone interiors library + test page. Every shop door opens
into a unique, seeded, themed interior, generated on demand in ~4ms, byte-identical every revisit.*

Last updated: 2026-07-14 · owner: PROCITY-C · reviewer: Fable

---

## What shipped

All files under my lane's ownership (`web/js/interiors/*`, `web/interior_test.html`) — no other lane's
files touched. Lane A's `core/registry.js` hadn't landed, so the lane is **fully standalone** (its 9
type recipes live in `theme.js`) with a `mergeRegistry()` hook for Lane F to wire the registry later.

| file | role |
|---|---|
| [interiors.js](web/js/interiors/interiors.js) | **public API** — `buildInterior(shop, THREE, opts)` |
| [theme.js](web/js/interiors/theme.js) | 9 shop-type recipes (archetype/wallpaper/floor bias, clutter, counter pos, fittings mix, stock kind, signage) + aliasing + registry-override hook |
| [shell.js](web/js/interiors/shell.js) | room shell: floor/walls/ceiling from lot×archetype, glazed shopfront + street backdrop, blocked back doorway, interior lighting |
| [fittings.js](web/js/interiors/fittings.js) | parametric fittings kit (ported from 90sDJsim + extended): bins, crates, racks, 4 shelf types, VHS aisle, glass case, counter+till, fridge, magazine/spinner racks, armchair, escalator, pegboard, barred window, returns slot, art frames |
| [layout.js](web/js/interiors/layout.js) | the placer: per-archetype zones, shuffled wall-slot system, occupancy grid, **guaranteed door→counter flood-fill path** |
| [stock.js](web/js/interiors/stock.js) | v1 visual stock: pooled canvas-texture sleeves/spines/boxes/garments/snacks with price stickers (dig.js trick) + `stockAdapter` hook for BaseGod data |
| [context.js](web/js/interiors/context.js) | build/dispose/seed backbone: independent seeded sub-streams, shared-geometry cache, leak-free `disposeAll()` |
| [glb.js](web/js/interiors/glb.js) | **optional** GLB hero-prop upgrade — reads Lane E's `manifest.json`, swaps primitives for depot GLBs, placeholder-persists. OFF by default; primitive fallback always |
| [interior_test.html](web/interior_test.html) | standalone test page (below) |

## Public API (the contract Lane B/F build against)

```js
import { buildInterior } from './js/interiors/interiors.js';
import * as THREE from 'three';

const room = buildInterior(shop, THREE, opts?);
scene.add(room.group);
// … player walks; on hitting room.exits[i], fire procity:exitShop …
room.dispose();               // frees ALL per-room GPU resources; removes group from parent

// room = {
//   group,                              // THREE.Group, self-contained (lights included)
//   spawn: { x, z, ry },                // enter just inside the door, facing −Z (into the shop)
//   exits: [ { x, z, w, toStreet } ],   // door back to street
//   places: [ …meshes w/ userData ],    // interactables: counter, bin, case, fridge, returns, exit
//   dims: { W, D, H, archetype, type },
//   placement,                          // deterministic summary (deep-equal per seed)
//   pathOK, buildMs, counts(), dispose()
// }
```

`shop` is tolerant — recognized fields `{ id, type, name, seed, storeys, lot:{w,d} }`:
- **seed** (uint32) is the ONLY randomness source; falls back to a hash of id/name/type if absent.
- **type** — any CITY_SPEC type (`record opshop toy book video pawn milkbar dept stall`) **or** a
  thriftgod/Overpass alias (`music charity pawnbroker market video_games …`); defaults to `opshop`.
- **lot** `{w,d}` metres — the room adapts to it (never exceeds it); absent → archetype ranges decide.
- **storeys** drives ceiling height 3.2–4.5m.
- `opts`: `{ archetype?: 'cosy'|'gallery'|'wide'|'hall'|'pokey', stockAdapter?, useGLB?, manifest?, manifestUrl? }`.
  Registry override is a **one-time global** — `import { mergeRegistry } from interiors.js; mergeRegistry(registry)`
  at init (NOT a per-build opt — a per-call mutation of the shared recipe table would break same-seed determinism).

**Coordinate convention** (shared with a future Lane B wiring): `+Z` = door/street side, `−Z` = back,
origin = room centre, floor `y = 0`. Everything is in the returned `group`'s local space.

### For Lane B (door wiring, later)
`buildInterior` is a pure function — call it on `procity:enterShop`, add `room.group` to the scene,
teleport the player to `room.spawn`. On `procity:exitShop` (player reaches `room.exits[0]`) call
`room.dispose()` and restore the street. The street window fake is Lane B's; I own the inside view
(a bright canvas street backdrop plane is already behind the glazing).

### For content phase (BaseGod / GODVERSE)
Pass `opts.stockAdapter = (shop, slotKind) => ({ texture }) | ({ mesh }) | null`. Returning a texture
skins that stock item's face; a mesh replaces the item; null → procedural placeholder. No layout/
fittings changes needed. `slotKind ∈ { sleeve, spine, box, snack, magazine, garment, treasure }`.

## Test page — `web/interior_test.html`

Serve: `cd web && python3 -m http.server 8130` → open `/interior_test.html`.
- seed input · type dropdown (9) · archetype override (auto + 5) · lot `w×d`/auto · re-roll · seed ±
- first-person walk (PointerLock + WASD) with occupancy-grid collision + room clamp
- debug toggles: **wireframe** (F), **occupancy grid** (G), **path** (spawn/counter markers)
- **▶ 50-room soak test**: builds+disposes 50 seeded rooms, asserts ms/room, leaked geometries vs
  baseline, and determinism (same seed → identical placement)

## Acceptance — all met

| requirement | result |
|---|---|
| Same seed twice → identical room (deep-equal placement) | ✅ 0 mismatches / 810 builds |
| All 9 types × 5 archetypes render sensibly | ✅ contact sheet `docs/shots/laneC/_grid_9types_5archetypes.jpg` |
| Build < 50ms/room | ✅ steady-state ~4ms, clean-soak worst ~8ms (first-ever build ~60ms one-time cold-JIT; occasional ~60ms GC pauses only under back-to-back torture loops — not a real per-room cost) |
| Dispose leak-free (info.memory → baseline) | ✅ soak leak: geo 0, tex 0 |
| Flood-fill door→counter always exists | ✅ 0 path-fails, 0 carves / 810 builds |
| Runs with zero assets & zero network | ✅ seeded flat-colour fallback under every texture; map only assigned on load |

**Full sweep** (9 types × {auto+5 archetypes} × 3 seeds × {null,4×4,5×14,20×20,3×3} lots = 810 builds):
`throws 0 · pathFail 0 · determinismFail 0 · carved 0`. Warm perf: all < 50ms (worst 33.2ms).
**Soak** (50 rooms): `avg 4.0ms · worst 9.6ms · leakGeo 0 · leakTex 0 · detFail 0 · pathFail 0`.

## Key decisions & notes for review

- **90sDJsim `fittings.js` ported** (it was written to be lifted): `clothesRack`, `shelfUnit`,
  `recordBin`, `table`, `counter`, `pegboard`, garment-silhouette canvas trick. Extended with the
  fittings CITY_SPEC's registry needs (cube/metal/book/VHS shelving, glass case, fridge, spinner,
  magazine rack, armchair, escalator prop, returns slot, barred window, listening corner).
- **thriftgod `buildShop` ported**: the 5 archetypes, the shuffled wall-slot system, bins with fanned
  sleeves wearing covers, corner counter+till, crooked wall art, blocked back doorway.
- **Determinism** via independent seeded sub-streams keyed by a salt string (`ctx.stream('wallpaper')`
  etc.) so adding a fitting in one subsystem never shifts another subsystem's picks.
- **Leak-free** via a tracked build context: per-room geometry/material/CanvasTexture/tiled-file-texture
  are freed in `dispose()`; globally-cached file textures (`core/loaders.loadTex`) are shared and not
  disposed (bounded cache). Dispose-before-texture-load race is guarded (`_disposed`).
- **Perf**: shared-geometry cache (`ctx.boxGeo/planeGeo/cylGeo`) collapses the hundreds of identical
  stock items in a room down to ~80–110 geometries; spine density tuned so a book barn is ~600 meshes.
- **GLB upgrades**: `web/assets/manifest.json` (Lane E) is read if present, primitive fallback always.
  Not present yet → 100% primitives, which is why the test page runs asset-free.

## Integration with sibling lanes (landed in parallel)
- **Lane A `core/registry.js`** — its `SHOP_TYPE_IDS` match my 9 recipe keys exactly. I kept the
  interior recipes local (the registry doesn't carry archetype-bias/clutter/counter-pos/stock detail),
  with `mergeRegistry()` as the one-time override seam for Lane F.
- **Lane E `web/assets/manifest.json`** — its `fittings` section (9 depot GLBs with footprints) is now
  wired through `glb.js` (opt-in `useGLB`, primitive fallback). Depot GLBs may not be uploaded yet;
  verified the fallback (unreachable depot → primitives persist, no crash, no leak).

## Adversarial review — 5 findings, all fixed

Ran a 5-dimension adversarial multi-agent review (determinism / disposal-leaks / path-guarantee /
three-api / edge-robustness) with a per-finding verify pass. 5 real defects surfaced; all fixed and
re-verified (830-build sweep + 50-room soak green after each fix):

| # | sev | file | defect | fix |
|---|---|---|---|---|
| 1 | med | interiors.js | per-build `opts.registry` permanently mutated the shared recipe table → latent same-seed determinism break across differing registry states | removed per-build option; registry override is now a one-time global `mergeRegistry()` (Lane F setup) |
| 2 | low | interiors.js | explicit `null` opts threw (`opts = {}` default only covers `undefined`) | normalize `opts = opts \|\| {}` |
| 3 | low | shell.js | empty `archetypeBias` array → `bias[0][0]` on `[]` throws | fall back to uniform bias when missing **or** empty |
| 4 | med | layout.js | fittings pulled by the path loop left phantom interactables in `places` (dangling after dispose) | collect `places` from survivors at the end, not incrementally at placement |
| 5 | low | layout.js | `rebuildOcc` re-stamped wall-mounted fittings that `placeAtWall` never stamped → phantom floor obstacles after a blocker-pull | mark wall-mounted `noStamp`; skip in `rebuildOcc` **and** exclude from the removable pool |

Verify evidence (post-fix): `nullOpts ok · phantomPlaces 0/332 · determinismAcrossBuilds identical ·
emptyBias ok · sweep 810 {throws 0, pathFail 0, detFail 0} · soak {avg 4.2ms, worst 8ms, leakGeo 0,
leakTex 0}`. (Reviewers also confirmed no disposal/leak or three.js-contract defects.)

## Not done (out of scope for v1 / depends on other lanes)
- Real item data / economy (content phase — `stockAdapter` hook is ready).
- GLB hero props are **wired** (`glb.js`, opt-in) but not visually validated end-to-end — needs the
  depot GLBs actually uploaded (Lane E) + `useGLB` flipped on by Lane B/F. Primitive path is the tested baseline.
- Interior-mapping shader for street windows (Lane B stretch goal).
- Back-room beyond the blocked doorway (v2).