# Lane E — FX HANDOFF (`src/fx/**`)

Owned by Lane E. See `src/audio/HANDOFF.md` for the full lane summary.

## Public API

```ts
const fx = new FxSystem({
  scene,                       // THREE.Object3D to add fx to (Lane A's scene)
  setEmissiveBoost,            // Lane A's injected hook (v:number)=>void
  getLevels: () => audio.getLevels(),
});
fx.update(dt);                 // each fixed tick
```

`FxSystem` self-wires to the bus (`audio:beat`, `signal:repair`, `game:win`,
`platter:state`, `block:break`) and adds all its own objects to `scene`.

## What's in here

- `particles.ts` — `Burst` (round-robin, finite-life pool: break puffs, win
  confetti, 45-rpm rim sparkle) and `DustField` (continuous brownian motes).
  Both preallocate typed arrays and mutate them in place — **zero per-frame
  allocation**; a shared canvas glow texture, no external assets.
- `overlays.ts` — emissive sprite overlays we own (never touching Lane A/C
  materials): `VuBank` (mixer VU towers, LED-segment stacks keyed to
  `getLevels()`), `SignalTrace` (a bright sprite that runs the signal-path
  polyline on each repair), `PatchBlink` (patch-bay socket blink).
- `layout.ts` — all overlay anchor points derived from `src/core/constants.ts`
  `LAYOUT` (VU towers, `SIGNAL_PATH`, patch bay, dust box, deck rims).
- `FxSystem.ts` — orchestrator: the global LED emissive pulse (base steps up
  per repair, pulses on beats), rim sparkle, and the win visual timeline
  (1.8 s dark → needle-drop flash + confetti → living-booth steady state).

## Notes for integration

- The only material Lane E touches is via the injected `setEmissiveBoost`.
- VU/trace/patch positions come from `LAYOUT`; if Lane C's real LED towers sit
  elsewhere, adjust `VU_TOWERS` in `layout.ts` (see friction #5 in the audio
  handoff).
- `update(dt)` is safe at `FIXED_DT`; the win visual timeline advances on the
  `dt` you pass (keep calling it every tick so it doesn't stall mid-sequence).

## Round 2 — Headshell Workshop

- **Screw confetti**: `FxSystem` auto-tosses a burst of brushed-steel screws
  when the workshop completes — it reacts to `signal:repair` with
  `node === 'stylus'` (Lane D calls `quest.repair('stylus')`). Also exposed as
  a public `fx.screwBurst(x, y, z)` for explicit use.
- **The oscilloscope scope block is Lane D's** (`src/machines/workshop/`, its
  own canvas draw). Lane E does NOT render a scope — an earlier `src/fx/scope.ts`
  was removed to avoid two scopes.

## Glow-Up G3 + G5 — decals (`src/fx/decals.ts`)

Screen-print decals + the record groove texture. Built once, purely cosmetic.

```ts
import { DecalSet, recordSideTexture } from './fx/decals';
const decals = new DecalSet();   // no deps
scene.add(decals.group);         // ~13 plane meshes (< 25 draw-call budget)
decals.dispose();                // frees geometries + canvas textures
```

- **G3** bakes text/markings onto `CanvasTexture`s applied to thin planes
  floating `0.05` proud with `polygonOffset` (no z-fight, verified at grazing
  angle). One canvas per gear piece keeps the count low. Positions come from
  `LAYOUT` (`core/constants.ts`) and the worldgen anchors
  (`MIXER`/`DECK_A`/`DECK_B`/`PATCH`/`UNDER`) — nothing hardcoded. Print set:
  mixer `CH 1–4` + fader ticks + `TURNCRAFT-800` + crossfader `A↔B`; each deck
  `START·STOP`/`33`/`45`, a pitch `+/−` ladder, and a "Quartz Direct Drive"
  plinth-front script; patch-bay `PATCH BAY` + `01–12` socket numbers; a
  `FUSE 250V` legend; and four procedural party flyers on the booth walls.
- Flat (`up`) faces flip each glyph 180° in place so labels read from the
  player's front-edge viewpoint (tick marks / positions stay put).

### G5 — `recordSideTexture(): THREE.CanvasTexture`  ← **Lane D wires this**

**Signature:** `recordSideTexture(): THREE.CanvasTexture` — no args; returns an
8×128 sRGB canvas texture, `RepeatWrapping` (S+T) + `NearestFilter` already set,
near-white base with fine dark groove lands so it **multiplies** cleanly over
the tier's existing vinyl tint.

A fine light/dark groove-ring texture for the vinyl tier **side** cylinders.
Rings run horizontally (constant around the circumference, varying up the
height). **This lane does not edit `platter.ts`.**

**Exact merge point — `src/machines/platter.ts`, the `sideMat` around L121–124**
(where `sideMat = blockMaterial(vinylId, { opacity … })` is built and applied to
the outer + mid vinyl tier side cylinders):

```ts
import { recordSideTexture } from '../fx/decals';
// after: const sideMat = blockMaterial(vinylId, { opacity: ... });
sideMat.map = recordSideTexture();
sideMat.map.repeat.set(1, Math.max(1, tierHeightVox / 4)); // ~4 grooves/voxel of height
sideMat.needsUpdate = true;
// NearestFilter + RepeatWrapping are already set on the texture. No geometry or
// platter-logic change — purely a `material.map` assignment.
```

It's a standalone generator (no side effects); safe to call once and share the
texture across both platters. Only the platter wiring is left — everything else
here is live and browser-verified.