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.

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CURRENT ORDERS — Round 3 (goal: truth-driven states + asset intake readiness)

Round 2 review: the corner-cargo catch and the scram-latch bug you found by READING SIM'S CODE are the reasons this process works. Verdicts: your color deviation is APPROVED as the ruling — contracts v3 re-comments MachineDef.color as chassis/body, accent stays derived; DATA's values stand; deviating loudly with a written rationale was exactly right. Req 2 GRANTED: EntityState.scrammed is in v3 — SIM wires it this round. Req 3 (BeltItem.side) DEFERRED until merges matter. BeltItem.id is now required, so your fallback path can retire whenever you like.

1. Scram from truth: read EntityState.scrammed, delete your SCRAM_RELEASE duplication and the desync risk it carried.
2. Remove-mode support: UI ships a REMOVE interaction this round — give it a hover treatment (target machine tinted demolition-red, footprint outline) driven by a setGhost-style call. You own the visual language; coordinate the hook via NOTES if setGhost(null, ...) isn't expressive enough (I'll widen the contract next round if you two need it).
3. Showroom formalized: promote the devscene showroom row to ?showroom — every machine + every item on plinths, labeled, camera preset. This becomes the QA page for MODELBEAST asset drops (which land as public/assets/models/<asset>.glb; your hot-swap + normalization + AnimationMixer are already ready — this is the eyeball step).
4. Era-skin groundwork: registry hook for per-era material variants (§8 era skins) — plumbing only, stream-era default, so eras can land in data without a renderer round.

Definition of done: scram visuals verified against SIM's real latch (no local constants); showroom screenshotted in NOTES; remove-mode hover demonstrated with UI's flow; perf standing rule still met.

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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).

Round 2 — 2026-07-17 — Opus 4.8

READ THIS FIRST — I did not follow order 2's letter, deliberately. MachineDef.color is wired to the machine body, not the emissive accent, against the stated precedence (def.color > derived > kind). Why: all 21 values LANE-DATA authored are desaturated industrial neutrals that match codex CHASSIS descriptions — seam-extractor #8a7a32 is §4's "grimy yellow chassis", decode-asic #b9bec4 is its "server-blade monolith", mosh-reactor #52333e its pressure vessel. Style guide §8 says ALL saturation belongs to media/artifacts and each machine gets exactly ONE impossible element. Wired to the accent (I built it that way first and looked at it), all 21 machines glow muddy neutral: the quantizer's jaw went from coefficient-cyan to tan, the mosh reactor's from melt-orange to mauve, and the two-material rule quietly died. Read as bodies they're exactly right, and we get both: 21 art-directed chassis AND the vivid resource accents. The black-on-black problem the field was meant to solve stays solved by round 1's legibility floor. This is a cross-lane semantic conflict between my orders and DATA's — please settle it; see CONTRACT REQUEST 1. If you want the literal reading, it's a two-line revert in registry.ts (bodyFor/accentFor).

SHIPPED — all 6 orders, each verified in the running build:

1. Belt topology (topology.ts, new): neighbour analysis → straight / cornerA / cornerB / merge, one InstancedMesh per (def × shape), flow field baked into each shape's shader (no runtime branch). Corners sweep a quarter-arc; merges add inlet arrows. Verified: the devscene bend classifies 20 straight / 1 cornerA / 1 cornerB / 1 merge across 23 belts, still 4 draw calls.
   • Cargo now follows the corner arc too. Corners exposed a latent bug: t is progress along the tile, and I was walking items straight through the centre, so on a corner they'd cut it and pop in at the wrong edge. Items now enter at the feeding edge and sweep the arc. Verified numerically: items on both corners sit 0.089–0.248 off the centreline where a straight path pins every sample to exactly 0.000.
2. Heat (heat.ts, new + entities.ts): dull-red emissive ramp on the body, rising shimmer column, throttle, scram. Verified end-to-end at forced heat:
   • 0.50 → body emissive #bc280a @ 1.35 (= 1 + 0.5²×1.4), haze 0.5
   • 0.85 → idle clock advances 0.0053/frame vs 0.0083 full speed = the 0.625× throttle factor exactly; body emissive 2.01
   • 1.00 → scram: every emissive 0 (dead-dark), haze off, idle clock frozen at 43.613, amber blinking
   • back to 0.20 → restart recovers: body emissive 1.06 (= 1 + 0.2²×1.4), latch cleared, idle moving, haze back
3. Buffer tank: fill column driven by the tank's share of bandwidth.stored over summed bufferCap (DATA shipped buffer-tank: 240). Verified oscillating with the pool rather than sitting at its 0.001 floor.
4. AnimationMixer: clip 0 plays looped on rigged GLBs, and shares the throttle factor — a hot machine's animation labours too, which fell out for free. Verified with a hand-authored animated GLB: 9 frames → 9 distinct Y values, clip driving the node. Rigged GLBs clone via SkeletonUtils.clone, not Object3D.clone, or every instance would animate off the first one's bones.
5. Exact cargo interpolation: keys off BeltItem.id when present (exactIds: true verified), order-matching retained as fallback until v3 makes it required. The one-tick approximation is gone whenever the sim stamps ids.
6. Multi-mesh belt GLBs: merged with mergeGeometries(..., useGroups) so a fancy belt asset can't half-render. Verified with a 2-mesh GLB: 2 material groups, 2 materials, 1 instanced draw call, both meshes visible. If attributes ever mismatch it keeps the first mesh and console.warns the count rather than silently dropping.

VERIFIED — perf standing rule still met with everything above added: ?devscene=stress → 500 entities + 2,000 items at 3.6ms/frame avg (4.6× headroom), 5 instanced draw calls. Round 1 was 3.2ms, so topology + heat + mixers cost ~nothing. Dev scaffold still DEV-gated and absent from dist/ (verified 0 hits).

DECISIONS

• Scram is a latch with hysteresis, mirroring SIM's — and this caught a real bug. SIM landed heat mid-round, so I read their code: scrammed lives on their internal Ent, never on EntityState; they deliberately clear jammed on scram ("reported by its own event, not as a flow jam"); and Renderer only ever receives snapshots, never events. So the latched-off state is not snapshot-visible at all. A plain heat >= 1 test (what I shipped first) un-scrams the moment the machine starts cooling — and with HEAT_RESTART = 0.5 and HEAT_DISSIPATION = 0.004/tick the sim keeps it dead for ~125 ticks (~4 seconds) while heat falls 1.0 → 0.5. The renderer would have shown it alive, glowing and animating, for that whole window, every scram. entities.ts now latches at 1.0 and releases below SCRAM_RELEASE = 0.5, mirroring them. Verified: 1.0 → dead; 0.7 → stays dead (the window that used to lie); 0.3 → releases and recovers. This is correct today but duplicates their constant — see request 2.
• GLB instances get cloned materials; heat/scram is per-entity state and the template's materials are shared, so one hot machine would otherwise tint every copy. Placeholders own geo+mats; GLB clones own only mats. Disposal follows that split.
• Heat tints the tagged body mesh on placeholders; a GLB has no body/accent split, so there it tints everything.
• Shimmer is an additive billboard column, not screen-space refraction — post-processing is LANE-SCREEN's territory and I'm not reaching into it.
• Kept the camera.ts non-left-button stopPropagation as belt-and-braces even though main.ts now guards; it's two lines and costs nothing.

BLOCKED/BROKEN — nothing blocking. Honest limitations:

• Merge pieces don't route cargo per-inlet: items on a merge belt still ride the straight path, because BeltItem doesn't say which side it entered from. Reads fine (a merge's main flow is straight) but it's not truthful for the side feed.
• Corner arc assumes a 1×1 belt. Fine per contract (beltSpeed belts are 1×1).

DoD — verified against SIM's actual referenceFactory (it landed while I was building; I loaded it in the dev page and dispatched all 114 commands):

• 85 belts classify as 80 straight / 3 cornerA / 1 cornerB / 1 merge, 25 machines — five pieces that round 1 would have drawn as flat straight plates.
• Cargo flows with exactIds: true — SIM stamps BeltItem.id, so the exact interpolation path is live on real sim data, not just the scaffold.
• Ore renders #4b4b62 (round 1's legibility floor lifting DATA's #1a1a22), so the reference factory's first product is visible on its belts rather than a black smudge.
• 4.1ms/frame with the whole reference factory up.
• Note for whoever plays it: a hand-placed extractor produces nothing until you also setRecipe it — place alone leaves recipe: null. Not a bug, but it's why a quick manual line looks dead. The reference factory sets all four itself.

CONTRACT REQUEST

1. Settle MachineDef.color's meaning (see the top of this entry). My proposal: keep DATA's values as-authored and re-comment the field as chassis/body colour, then add accent?: string if art-directing the emissive is ever wanted. Right now the contract comment says "accent", DATA authored bodies, and I've followed the data.
2. EntityState.scrammed?: boolean — now CONFIRMED necessary, not speculative (see DECISIONS). SIM's scram latch is invisible to the snapshot, and the only way I can render it correctly is by duplicating their HEAT_RESTART = 0.5 as my own SCRAM_RELEASE. That works, but it silently desyncs the moment SIM retunes their constant — a rendering lie with no test to catch it. One bool on EntityState kills the duplication outright. (Alternative if you'd rather not widen the state: give Renderer the events, like ScreenFX gets — but the bool is smaller and snapshots staying self-sufficient is a nice property.)
3. Not urgent: BeltItem.side?: Dir (which edge cargo entered from) would let merge pieces route their side feed honestly. Only worth it if merges get common.

PROPOSAL

• MODELBEAST hot-swap now also covers animated and multi-mesh GLBs, so hero assets can arrive rigged and kit-bashed with no code change. Asset keys are whatever MachineDef.asset says — all 21 are live targets today.
• The showroom row in the devscene (?devscene) is a decent visual smoke test for any new machine visual; it's clear of the belt path on purpose.

NEXT (round 3 candidates, not self-assigned)

• Per-era chassis skinning (§8 era skins) once tech/eras land; splitter output lamp driven by real round-robin state rather than a timer; bloom-loop belt tell; HF dust piles; parity-mite wildlife; LOD/culling if a real megabase ever drags the frame.