FORGEKUBO · DETAILED IMPLEMENTATION PLAN · AUG 23, 2026

Kubota M7-154 M7-4 · Tractor + Living Field

Make the machine specific. Make every pass change the field.

A source-auditable plan to refine the live ForgeKubo tractor toward the exact M7-154 reference, preserve believable implement behavior, and turn the existing cutting effect into persistent local grass that shortens under the mower and regrows over time.

Executive decision

Run two coordinated workstreams—not a rewrite. Replace provisional tractor geometry and runtime mesh surgery with an authored M7-154 rig. In parallel, extract cut state into a versioned coverage model that records where and when the deck passed, drives real grass geometry, survives handoff/reload, and regrows locally.

25.5 MBcurrent tractor transfer payload; ceiling, not target

500Kcurrent tractor triangles in one baked mesh

0.78→0.13 mstanding hay to current stubble height

120 srequired full-cut hold before local regrowth

Current State → Envisioned Outcome

AFTER images are AI-generated design-target concepts, not evidence of implemented functionality. They use each live simulator frame as the composition reference and visualize the intended M7-154 fidelity, mechanically credible cutter, deck-aligned shortening, and local regrowth. The BEFORE images remain the production baseline.

Chase View

Primary exterior quality gate: model-specific tractor detail, credible hitch/driveline, and an immediately readable fresh-cut lane behind the deck.

AI concept showing the envisioned M7-154 and regrowing grass in chase view — Envisioned target: authored M7-154 details, plausible rear connection, deck-width short stubble, fresh residue, and older grass returning locally.

Aerial View

Spatial behavior gate: the mower footprint, active pass, overlap, and differently aged areas should read without a fake coverage overlay.

AI concept showing deck-aligned mowing and local grass regrowth from the aerial view — Envisioned target: tall grass ahead, a fresh short swath behind, overlap evidence, and older irregular patches progressing through regrowth.

Top View

Geometry proof gate: coverage must follow the actual cutter width and swept path, preserve guidance alignment, and never show square cells or teleport streaks.

AI concept showing exact mower-width cutting and regrowth from the top view — Envisioned target: deck-aligned short grass, fresh and older zones, natural boundaries, visible overlap, and full-height standing grass elsewhere.

Verified dimensional anchors

Use the official M7-4 brochure as the source of record, then annotate the exact configuration. These anchors validate the model; they do not justify inventing option-dependent details.

M7-154M7-4 target model

4,770 mmoverall length

3,091 mmoverall height

2,794 mmlisted overall width

2,718 mmwheelbase

Target architecture

Approved references

M7-154 configuration matrix, brochure dimensions, approved exterior/cab imagery, hitch/RC5710 references, SME-confirmed machine behavior.

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Typed domain models

M7RigManifest validates named anchors and behavior status. coverage.ts owns swept cells, timestamps, regrowth, overlap, pruning, and serialization.

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Babylon scene modules

An authored GLB drives stable rig nodes. Terrain derives plant visuals from coverage state. React remains orchestration—not the source of machine or field truth.

Two coordinated workstreams

WORKSTREAM A

M7-154 fidelity

1 · Lock the configuration

Build a reference matrix for dimensions, hood/grille, Gen-4 lights, exhaust, tanks, steps, mirrors, roof, cab, tires, axle, hitch, PTO, links, RC5710 connection, steering, and eye point. Mark every item verified, provisional, conflicting, or missing.

2 · Measure the asset baseline

Inspect all shipped GLBs; record hierarchy, triangles, textures, dimensions, wheel centers/radii, wheelbase, hitch, cab mount, load/decode cost, and fixed-angle captures.

3 · Author the hierarchy offline

Export stable nodes for chassis, axle, four hubs/wheels, separate steering pivots, cab shell/glass/interior, mirrors/lights/steps/exhaust, hitch, PTO/driveline, links, mower pivot, and camera mount. Remove production runtime wheel/glass carving.

4 · Correct form before detail

Fix wheelbase, length, tire diameter, cab/hood ratio, track, stance, and ground clearance first; then Gen-4 features, cab, hitch, decals, materials, and controlled wear.

5 · Make motion measured

Use actual wheel radii, separate left/right Ackermann steering, four-point terrain contact, bounded axle/chassis motion, authored hitch articulation, mower terrain following, and the authored cab-eye anchor.

Exit gate: recognizably the approved M7-154 configuration; source-auditable dimensions/behavior; stable named rig; no floating tires, snapping implement, opaque-glass workaround, or runtime triangle surgery.

WORKSTREAM B

Living grass coverage

1 · Extract coverage state

Create a scene-independent sparse world-space lattice, initially 0.5 m cells. Each active cell stores a stable index, cutAt, optional pass/direction data, and schema version.

2 · Use real elapsed time

Cut immediately, hold at 0.13 m for 120 seconds, regrow locally over an initial 60-second tuning window, then prune the recovered cell. Recutting resets only that cell.

3 · Derive plants from coverage

Keep deterministic planting, thin instances, plant buckets, stubble silhouettes, and residue. Replace scene-local cutSlots as truth. Restore each plant's exact original matrix as its cell recovers.

4 · Reclaim transient geometry

Replace high-water-only stubble/residue pools with free lists so independently regrown cells can release and reuse instances without leaking capacity.

5 · Persist safely

Store sparse coverage separately from tractor state. Handoff/restart preserve it; reload advances age by wall clock and prunes expired cells; corrupt or unknown schema fails to clean grass without breaking startup.

Exit gate: deck-aligned cutting, two-minute hold, smooth local regrowth, recut, overlap accuracy, reload/handoff continuity, no grid pattern, no mass pop, no teleport streak, and bounded runtime/storage cost.

Grass lifecycle

Standing

Deterministic original plant matrix at full authored height with wind, variation, and field relief.

Cut

The authored deck sweep marks cells; standing instances hide; stubble and residue appear.

03 · 0–120 s

Hold

The region remains fully cut. New neighboring passes keep independent timestamps.

04 · TUNED

Regrow

Standing matrices return progressively while stubble and residue retire in spatially local bands.

Recovered

The cell is pruned. Recovered plants exactly match their deterministic original poses.

Implementation milestones

Evidence + baseline

Reference matrix, GLB forensics, fixed-angle captures, startup/frame metrics, exact configuration and missing-reference list.

Authored rig

Correct primary form, split hierarchy, materials, cab/glass, stable pivots, measured anchors, web export.

Behavior

Manifest validation, wheel radii, Ackermann steering, terrain contact, hitch/deck behavior, cab mount.

Coverage domain

Tests first: swept cells, overlap, hold, regrowth, recut, pruning, versioned serialization.

Terrain bridge

Coverage-driven plants, dirty buckets, reclaimable pools, progressive restoration, authored deck pose.

Continuity

Handoff/restart preservation, wall-clock reload, safe schema fallback, throttled storage writes.

Hardening

Full tests/build, browser QA, before/after captures, visual review, startup/frame/storage profiling.

Implementation detail that matters

Machine rules

Do not uniformly scale a wrong silhouette into compliance.
Stable named GLB nodes replace runtime triangle classification.
Each surface family gets physically plausible material treatment.
Each machine behavior is cited or explicitly provisional.
The current 25.5 MB tractor is the payload ceiling, not a quality target.
Equivalent-scene p95 frame time may not regress more than 5% without review.
Offline same-origin Meshopt/Draco startup remains mandatory.

Field rules

Coverage is world-space and independent of visual plant density.
Only dirty/aging buckets update, at a coarse cadence—not every plant every frame.
The mower deck transform and physical width drive the sweep.
Overlap changes pass spacing, not deck geometry.
Coverage area counts unique cells, not distance traveled.
Teleports, resets, restores, and boundary corrections never sweep.
Closing the tab does not pause regrowth.

Test and proof matrix

Required rig nodes load or fail visibly.
Manifest bounds and anchors match the approved configuration.
Four wheel centers/radii are measured and valid.
Wheel roll follows signed ground distance.
Inside/outside steering angles diverge correctly.
Motion converges at 30/60/120 fps.
Tire contact survives representative relief.
Hitch/deck articulation avoids tire intersections.
Cab mount stays synchronized with the chassis.
Offline decoder startup passes.
Straight and curved sweeps mark expected cells.
Overlap never double-counts area.
Recut resets local age.
No cell regrows before 120 seconds.
Only aged cells regrow.
Reload advances by real elapsed time.
Handoff/restart preserve active coverage.
Teleport/reset produces no cut path.
Corrupt storage falls back safely.
Pool usage remains bounded across repeated cycles.

Definition of done

The asset is measurably the approved M7-154 M7-4 configuration—not a generic M7 approximation.
The production rig uses an authored node hierarchy with source-auditable anchors and behaviors.
Wheels, steering, terrain contact, cab, hitch, and mower move from measured rig geometry.
The actual mower deck sweep shortens real grass geometry.
Every region holds cut for 120 seconds, regrows progressively/locally, and can be recut.
Handoff, guidance restart, and reload preserve still-active coverage while neutralizing unsafe controls.
Teleports never create false swaths; repeated cycles never leak coverage or geometry capacity.
Unit tests, typecheck, production build, browser smoke, fixed-angle visual review, and measured performance gates pass.

Inputs still needed

Reference decisions

Exact M7-154 grade/transmission and axle.
Tire and wheel-spacing configuration.
Front weight, mirror, roof/light, and hitch options.
Approved exterior/cab reference pack.
Approved RC5710 connection and working-position references.

Behavior decisions

Verified steering response, lock, and turning radius.
Verified front-axle and implement behavior.
Whether the prototype needs explicit PTO/deck engagement.
Approved reviewer for final reference-matrix sign-off.
Target hardware/browser set for frame-budget certification.

Primary source: Kubota M7-4 Series brochure. Code baseline inspected in apps/forgekubo/src/openworld/scene/tractor.ts, terrain.ts, vehicleMotion.ts, persistence.ts, and the durable ForgeKubo vehicle/experience plans. Screenshots are from the live ForgeKubo simulator. This unlisted preview is link-accessible, not private.