glytch/fktry/lanes/LANE-RENDER.md

# LANE-RENDER — three.js world renderer

You are an Opus 4.8 executor on the RENDER lane of FKTRY. Read `../MASTERPLAN.md` and
`../CONTRACTS.md` first; the world bible + visual style guide (§8) is
`../../docs/FKTRY_LORE.md` — §8 is YOUR section, follow it.

**Mission:** make the Bitstream visible. Isometric factory view, machines, belts with
smoothly interpolated items, ghosts, selection — and the hot-swap pipeline that lets
MODELBEAST GLB assets land mid-development without a code change.

**Owned paths:** `src/render/**`, `public/assets/**` (manifest + loading; the files
themselves arrive from MODELBEAST).
**Never touch:** contracts, main.ts, other lanes. Sim is truth: you render snapshots,
you never simulate. If motion looks wrong, interpolate better or note it — don't
"fix" positions locally.

**Standing rules (all rounds):**
- 60fps with 500 entities + 2,000 belt items on an M-series MacBook. Instanced meshes
  for belts/items from day one — you will not get to retrofit this later.
- Placeholder aesthetic is a feature: crisp box-primitive machines tinted per codex
  `color`, NOT gray cubes. Two-material rule even for placeholders: dark body + one
  emissive accent.
- Every entity mesh keys off `MachineDef.asset` / `ItemDef.id` through the registry —
  zero hard-coded ids.

---

## CURRENT ORDERS — Round 2 (goal: finish M1 polish, open M2 "PRESSURE")

Round 1 review: excellent — the hot-swap verification and the fog/CAM_DIST honesty
note were exactly right. Verdicts: req 1 GRANTED (`BeltItem.id?` in contracts v2 —
use when present, keep order-matching as fallback until v3 hardens it). Req 2 GRANTED
(`MachineDef.color?` — precedence: `def.color` > your derived-from-outputs >
kind accent; your derivation stays as the fallback, it was the right instinct).
Req 3 DONE (main.ts ignores non-left buttons; drop your camera.ts workaround or keep
it as belt-and-braces, your call).

1. **Belt topology visuals**: corner/junction pieces chosen from neighbor analysis —
   pure presentation, sim truth unchanged. Splitters (mechanics land this round in
   SIM) get a visible output-cycling tell.
2. **Heat**: shimmer + dull-red emissive ramp driven by `EntityState.heat`; throttled
   = idle animation visibly slowed; scram = dead-dark + blinking amber until restart.
3. **Buffer tank**: visible fill level (shader window or scale trick) proportional to
   the tank's share of `snapshot.bandwidth.stored`.
4. **AnimationMixer**: play clip 0 on rigged GLBs with an idle loop — MODELBEAST
   assets are imminent; verify with any animated GLB you can find or make.
5. **Exact cargo interpolation** via `BeltItem.id` — delete the one-tick approximation.
6. **Multi-mesh belt GLBs**: merge-or-group fix (your call, note it) so a fancy belt
   asset can't half-render.

**Definition of done:** reference factory (SIM ships it this round — coordinate via
their `src/sim/reference.ts` export in a dev page or test harness) looks ALIVE: corners
read as corners, heat reads as heat, tanks read as tanks; perf standing rule still met
under `?devscene=stress`.

---

## NOTES (append-only log, newest at bottom)

```
### Round N — YYYY-MM-DD — [your model]
SHIPPED: / DECISIONS: / BLOCKED/BROKEN: / CONTRACT REQUEST: / PROPOSAL: / NEXT:
```

### Round 1 — 2026-07-17 — Opus 4.8

**SHIPPED** — all 7 orders, each verified in the running dev build (not "should work"):
- **Camera/controls** (`camera.ts`): ortho iso, wheel zoom clamped 8..40, middle/right-drag
  pan, WASD+arrows, resize via ResizeObserver.
- **Ground** (`ground.ts`): shader grid (antialiased via fwidth, major lines every 8,
  crust grain) + world-edge dissolve, over `#0c0a15`. Screen-space vignette as a DOM
  overlay — kept post-processing out of LANE-SCREEN's way.
- **Registry + hot-swap** (`registry.ts`): placeholder factories per kind; probes
  `assets/models/<key>.glb` on init + every 10s in dev. **Verified live**: dropped a
  GLB into `public/assets/models/quantizer.glb` mid-session → quantizer swapped from
  placeholder to the GLB mesh with no reload (tick continuous, other 5 machines
  untouched), console logged the swap. Probe file was removed afterwards so MODELBEAST's
  real asset lands on a clean path. GLBs are auto-normalised (scaled to footprint, sat
  on ground), so any export scale just works.
- **Entities** (`entities.ts`), **belts** (`belts.ts`, instanced + chevron scroll),
  **belt items** (`beltitems.ts`, InstancedMesh per type, interpolated), **ghost +
  picking** (`ghost.ts`), jam blink + brownout dimming.

**VERIFIED (numbers, not vibes)**
- **Perf standing rule met with 5x headroom**: `?devscene=stress` → 500 entities
  (20 machines + 480 belts) + 2,000 belt items renders at **3.2ms/frame avg** (budget
  16.6ms). The 2,480 belts+items cost **5 instanced draw calls** total.
- **Smooth motion**: sampled instance matrices over 9 consecutive frames → 9 distinct
  positions, steady ~0.0166 tiles/frame (2 tiles/s on a 120Hz panel). Interpolating
  continuously, not stepping at 30tps.
- **Ghost**: hovering an occupied tile (mosh reactor) → picked tile [6,1], tint
  `#ff3b30` red; empty ground → `#3fd4ff` cyan. Driven through main.ts's real glue.
- **Brownout**: exposure 1.35 → 0.644 with flicker. **Jam**: amber `#ffa726`, blinking.

**DECISIONS** (flagging these because they're judgement calls, not obvious readings)
- **Machine accent colour is derived from data**: `MachineDef` has no `color` field, so
  a machine's one emissive accent = the colour of the item it makes (recipes → outputs →
  `ItemDef.color`). Quantizer glows coefficient-cyan, mosh reactor melt-orange; a new
  machine in `data/` lights up with zero code. Matches §8's "colour = value = literally
  the resource". See CONTRACT REQUEST below.
- **Legibility floor on data colours.** Raw products are near-black by design (MDAT ORE
  `#1a1a22`). Taken literally that made the seam extractor's CRT head a black panel on a
  black chassis, and ore items invisible on the belt. Derived accents below L=0.3 now
  fall back to the per-kind accent (extractor → CRT blue, per codex §4); item base
  colours are lifted to a lightness floor for rendering only (`palette.readable`). Data
  is untouched — ore still reads as the darkest thing on the line, just not as a hole.
- **Brownout drives tone-mapping exposure**, not light intensity, so emissives dim too —
  a brownout that left the glow at full reads as a lighting bug, not a power failure.
- **Fog is banded around the camera distance**, not absolute. Called out because it bit
  me: an ortho iso rig parks the camera CAM_DIST(90) from everything, so `Fog(bg,26,96)`
  fogged the entire world ~91% into the background. Anything touching `CAM_DIST` must
  keep `index.ts`'s fog band in step.
- Dev scaffold (`devscene.ts`) is gated behind `import.meta.env.DEV` **and** `?devscene`,
  and is tree-shaken out of the prod bundle (verified: 0 hits in `dist/`). It yields
  automatically the moment the real sim reports any entity — it never fabricates over
  live sim data. `?devscene=stress` is the perf rig.

**BLOCKED/BROKEN** — nothing blocking. Honest limitations:
- **Belt GLB instancing takes only the FIRST mesh** of a multi-mesh GLB. Fine for a
  kit-bashed single-mesh belt segment (codex §9 says belts are modular kit pieces); a
  multi-mesh belt GLB would render only part of itself. Machines are unaffected.
- **GLB animation clips are not played** (no AnimationMixer yet). Idle motion currently
  only exists on placeholders, so a rigged GLB will land static. Wanted for M4.
- **Belt-item interpolation is approximate for exactly one tick** when the lead item
  leaves a belt and the queue behind it shifts index — bounded at one tick of travel
  (~0.07 tiles), imperceptible. Root cause is the missing stable id; see below.
- Below 30fps the interpolation stretches (prev-tick snapshot may be >1 tick back).
  Not observed; noting it rather than hiding it.

**CONTRACT REQUEST**
1. `BeltItem.id` (stable, per-item) — would make cargo interpolation exact instead of
   order-matched. Low priority; current error is imperceptible.
2. `MachineDef.color?: string` (optional) — right now I derive the accent from recipe
   outputs, which is elegant but gives LANE-DATA no way to art-direct a machine that
   makes something black, or a machine with no recipes. Optional field, derived fallback.
3. **`main.ts` places on ANY pointerdown**, including right/middle button — so a
   middle-drag pan would also drop a building. I worked around it inside my lane
   (`camera.ts` stops non-left buttons from bubbling to `#game`), but the clean fix is
   `if (e.button !== 0) return;` in main.ts's handler. Flagging since it's your file.

**PROPOSAL**
- MODELBEAST asset keys are live now — the registry will hot-swap any of these the
  moment a GLB lands, no code change: `seam-extractor`, `belt`, `demuxer`, `quantizer`,
  `mosh-reactor`, `decode-asic`, `shipper` (+ whatever LANE-DATA adds; the key is
  `MachineDef.asset`). Hero assets (mosh reactor, muxer) are the ones worth `fal_trellis2`.
- Shadows are on (2048 map, tight ortho shadow camera). Cheap at current load; if a big
  factory drags, that's the first dial to turn.

**NEXT (round 2 candidates, not self-assigned)**
- AnimationMixer for rigged GLBs; per-era skinning hooks; splitter/lane visuals; heat
  shimmer + throttle read-out on the software decoder; belt corner/junction pieces
  (currently every belt is a straight plate regardless of neighbours).