---
name: tinyworld-island-and-planes
description: Use when changing the home island layout, edge dressing, undersides, autoincentive sponsor banner (now a top-left logo-adjacent DOM banner), plane/crop-duster flight paths, banner streamers, or which side of the island is "front".
---

# Tiny World Island & Planes

## Coordinate system + camera-facing side

- The home island is centred at world origin. Top of grass = `y = 0`. Underside
  of dirt slab + inverted stepped underside extends down from there.
- `GRID` (default 8, max 20, ranges from `HOME_GRID_MIN` to `HOME_GRID_MAX`) ×
  `TILE` (=1) sets the edge length. Half-width = `(GRID * TILE) / 2`.
- `DIRT_H = 0.55` — visible dirt block height.
- Default camera: `DEFAULT_AZIMUTH = π * 0.32`, `DEFAULT_POLAR = π * 0.30`
  → camera sits in the +X +Z quadrant looking back at origin. The **+Z face is
  the "front" of the island** (most camera-facing side).

## `buildHomeBorder()` flow

Defined ~line 16340. Rebuilds the island's undersides and edge dressing every
time the home grid changes:

```
clear homeBorderGroup children
vbox(... underside slab ...)
voxelInvertedSteppedRoof(... cascading underside ...)
addIslandRocketEngines(homeBorderGroup)
addIslandEdgeDressing(homeBorderGroup)    // tufts, rocks, dirt accents
(island front drape removed — autoincentive now a top-left logo-adjacent DOM banner)
prepareHomeBorderForRender(homeBorderGroup)
buildDistantWorlds()
buildUnderIslandClouds() (if defined)
```

Anything you add that should live on the island should be appended inside
`buildHomeBorder()` so it rebuilds correctly when the user changes
`#render-home-grid` (the home board size selector).

Some of the round underside pipes emit a faint output from their outer
(side-facing) end — clear **water**, **murky** brown water, or **steam** — via
the pipe-emitter system in `23-particles-clouds.js` (`registerPipeEmitter` /
`updatePipeEmitters`, ticked next to `updateSmoke`). `addIslandUtilityUnderside`
(`13-distant-dressing-ghost.js`) registers ~32% of pipe runs (split
water/murky/steam) at their end; `buildHomeBorder` calls `clearPipeEmitters`
first. Emitter coords are local to `homeBorderGroup`; particles live in
`xrWorldRoot`, are capped at 140, and only spawn when `camera.position.y < 4`
(underside in view). Water/murky fall under gravity; steam rises and expands.

The home island underside (slab + `voxelInvertedSteppedRoof`), the island
**edges** (`addIslandSideBacking`), and the underside **greebles**
(`addIslandUtilityUnderside` trays/clamps) now honour the **Voxel bevel**
setting (`renderVoxelBevel`): their `vbox` calls no longer pass `noBevel`/`skip*`
(which would route to the un-beveled `getOpenBoxGeometry`). `voxelInvertedSteppedRoof`
is shared, so editable islands and the new-island stamp underside bevel too.
Cost note: at max bevel (0.06) the merged homeBorder geometry grows ~13× (the
many tiny greebles each round), so keep bevel modest. The **distant ghost-island
dressing** (tiny far preview islands) intentionally stays `noBevel` for perf.

Island shell materials (`M.boardSide`, `M.boardSideEdge`, `M.islandUnder`,
`M.islandUnderD`) opt into the world-UV shader pass in `04-textures.js`.
Grass tile risers use `M.boardSide` and should read as dirt/soil directly under
the grass cap, not rock; keep that material on the `soil-side` texture family.
The dedicated strata side backing (`M.boardSideEdge`) can still show deeper
soil-to-rock banding lower down, while underside materials use
`textures/island-underside-voxel.png` (`texIslandUndersideVoxel`) so the bottom
reads as larger dark beveled voxel blocks; keep replacement shell art seamless
and power-of-two because Three.js repeats it with mipmaps. The shader pass
darkens a coarse horizontal/vertical side grid and lightly modulates each
block/underside cell in the fragment shader. It uses world position/normal
varyings, so the large merged side slabs read as chunky voxel blocks without
adding geometry or draw calls. `islandShellMaterial()` in `03-geometry-materials.js`
copies Lambert `onBeforeCompile` hooks and explicitly preserves `ShaderMaterial`
uniforms/source so the side-backing clone keeps the same coarse grid/strata
shader instead of falling back to a black shell.

Island edge strata is shader-driven on the side backing only:
`addIslandSideBacking` uses the dedicated `M.boardSideEdge` shader material for
lower dirt/rock backing. Do **not** restore the old continuous green grass-cap
carrier at the top edge: it reads as a thin floating strip around the island in
Build/tilt-down views. Per-cell terrain and mesh-terrain side walls own the top
edge; the backing should stay darker/lower behind greebles. Keep the four backing
faces widened by the edge outset so corners meet cleanly, and keep hidden faces
stripped with `skipTop` / `skipBottom` / interior-side skips. Keep the
side-carrier meshes out of static base merging so the shader stays inspectable;
do not add separate overlay panels or per-tile decal geometry for this effect.
The dirt/brown band in `island-side-strata-gpt.png` should match the darker
`soil-side`/`M.dirtRich` greeble palette, not bright orange. Keep the band near
the dark brown family used by side greeble blocks so the bitmap and geometry
read as one material.

Underside pipes and water details are material-driven: `M.utilityPipe`,
`M.utilityPipeD`, and `M.utilityClamp` use the internal `pipe-metal` canvas
texture; `M.waterFoam` and `M.waterfallFoamPuff` use the internal
`water-froth` canvas texture. Keep these procedural unless the user asks for a
specific bitmap, because they apply to many tiny utility meshes and particles.

## Editable-island LOD + whole-island select/delete

- Two gates decide an editable island's LOD: a **distance** gate
  (`editableIslandBaseDesiredLod`, full within `max(40, span*5.2)`) and a **count
  budget** (`editableIslandFullLodBudget`, now +8: all full up to 14 islands,
  then 12/11/10). Both were widened so a placed cluster of ~8 islands keeps its
  real base + per-cell surface instead of dropping to the flat `proxyGroup`
  (which is what "island without a base / different surface" was).
- **Click an island's side** (no cell/object there) with the Select tool to
  select the WHOLE island: `pickEditableIslandBody` (`18-scene-pick-xr.js`) walks
  up to `userData.editableIslandId` (excludes home). It outlines the island
  (`setIslandSelectionOutline`, a box-edges `LineSegments` child of `island.group`
  so it follows move/rotate) and raises the move gizmo.
- **Delete/Backspace** on a selected island (no cell selection) calls
  `removeEditableIsland` — undoable, because the world-history snapshot includes
  `serializeEditableIslands()`. It clears the island's board cells, moorings
  anchored to it, registries, and selection.

## Island placement: 4-side holograms

With the Island tool active, hovering an island shows a blank-island hologram on
each of its **4 free cardinal sides at once** (`37-island-placement-holos.js`,
reuses `islandPlacementSlots(anchor).slice(0,4)` + `makeBlankIsland` +
`makeGhostHoloMaterial`). Occupied sides and the home origin are filtered out
("minus blocked by anything"). Hovering a hologram highlights it (`uBase`
0.10->0.36, brighter blue, slight scale-up) via a per-frame raycast in
`updateIslandPlacementHolos(x,y)`; clicking a hologram places there. GOTCHA: hover-test the holos **first** and keep the anchor **sticky** — `pickTile` ignores the holos, so recomputing the anchor while hovering a hologram flips it to whatever (home/other island) sits behind it and rebuilds the holos out from under the cursor (they "disappear" on click). Only re-anchor when hovering a *different* island; keep holos over empty space
(`applyToolToCell` checks `islandPlacementHoloHoveredSlot()` first, before any
island-select). `selectTool` clears the holos when switching away; the holo
shader `uTime` ticks via `tickIslandPlacementHolos`. The single snap-to-slot
hologram path is bypassed for the Island tool. GOTCHA: when cloning the
ghost-outline hull, collect mesh nodes *before* `o.add(hull)` — adding during
`traverse` recurses into the new hull forever (stack overflow).

Newly placed editable islands warp in instead of popping into place. The effect
lives in `14-editable-islands-moorings.js`: `startEditableIslandWarpArrival()`
starts a short blue-white streak/tunnel + arrival flash, and
`tickEditableIslandWarpArrivals(dt)` runs **after** `updateEditableIslandLods()`
so it can override LOD visibility during the arrival. Default creation triggers
the effect, while restored/imported/stress-demo islands with `skipSave: true`
do not; use `warpIn: true` explicitly for future multiplayer join arrivals.
The final saved transform remains `island.positionX/Y/Z` + `rotationY`; the warp
only moves/scales the render group temporarily.

The **home island is not movable**: its editable surface lives in the shared
world grid (`worldGroup`, picked by logical gx/gz), while only `homeBorderGroup`
(the base) is its transform group — so dragging it would shift the base away from
the locked surface. `updateTransformGizmo` (`12-selection-tool.js`) refuses to
bind the move gizmo when `selectedEditableIsland().__home` is set (selecting a
home *engine* sets `selectedEditableIslandId = 'home'`, which previously let the
gizmo grab it). Sky/editable islands stay movable. Making the home island truly
relocatable as one piece would require re-parenting the home cells into a movable
group and routing their picking through that transform (as editable islands do).

Island engines (home + editable, `userData.editableIslandEngineId`) can only be
selected **from underneath**: `pickEditableIslandEngine` (`18-scene-pick-xr.js`)
early-returns `null` when `camera.position.y >= 0`. Otherwise a pick ray from
above passes through the board and grabs the engine hanging behind it. Mirrors
`pickTile`'s "refuse picks from below the surface" convention, inverted.

Home-island rocket engines keep their chunky voxel casing, but the animated
jet plume is a small set of static or simply X-flipped shader sheets. Do not
rebuild it as many per-layer flame cubes; the sheet approach keeps the
underside readable while staying cheap for large-island scenes. Keep older
voxel object builders as inactive legacy helpers rather than deleting them;
they may be useful again for alternate engine styles or detail settings.
The jet plume sheets are underside-only effects: `tickIslandRocketEngines`
hides `rocketPlumeSheet` meshes when the camera is above the engine/island
surface gate, and their compact sheet dimensions are guarded by
`tools/check.js`. Do not let them billboard through the board or become a
surface-level white/cyan cloud in normal build/play views.

## Autoincentive sponsor banner

The PNG/JPG ships inline as `AUTOINCENTIVE_BANNER_DATA_URL` (~41 KB base64
JPEG) so there's no extra HTTP. Same data URL feeds:

1. A fixed DOM banner next to the **top-left Tiny World wordmark**
   (`assets/twlogo-wordmark.png`, logo-only crop with the island removed) on
   wide screens, dropping below the logo at medium widths and hiding on phone widths
   (`<a id="brand-banner"><img id="brand-banner-img">`), src set by the
   `applyAutoincentiveSponsorLogo` IIFE. Clickable, opens
   `https://x.com/Autoincentiv3`. Hidden in showcase + XR via `.brand-banner`
   rules in `styles/tiny-world.css`.
2. The sponsor logo in the Workspace settings panel
   (`<img id="sponsor-logo-autoincentive">`, populated by the same IIFE).

The old 3D island front-facing drape (`buildIslandFrontBanner` /
`tickIslandBanners`, a flapping cloth mesh on the +Z side) has been **removed
from the scene**: the call in `buildHomeBorder()` (13-distant-dressing-ghost.js)
is gone, so the functions remain defined but inert (legacy). `tickIslandBanners`
still ticks but is a no-op while `islandBannerEntry` stays null.

If the user changes art, swap the data URL and the `2.5:1` aspect — width
fits ~`GRID * 0.7`.

## Plane / crop-duster system

Defined in the **crop duster route / state** section (~line 26200).

- 3-plane pool (`planes[]`), shown in formations or solo.
- Persisted setting `tinyworld:render:planesEnabled` controls the whole system
  and defaults off for now. When off, the GLB/textures are not loaded and
  hidden banners/crop-dust particles are cleared.
- Two run kinds chosen randomly each cycle:
  - `startDustingRun()` — uses `planDustingCurve()` to sweep over crop cells.
  - `startBannerRun()` — uses `planBannerCurve()` to fly **behind** the
    island so the towed text banner reads against the sky.
- `planBannerCurve()` places the path at `target.z - (GRID * 0.5) - (GRID * 2)`
  — i.e. ~2 island lengths behind the back edge. Altitude is
  `Math.max(renderCloudHeight + 0.2, FLIGHT_CRUISE_ALT - 1.6)` — a touch
  lower than the dusting cruise altitude.
- Engine sound is jet/rocket — use `foley-rocket-engines-1..4`, NOT
  `foley-propellers-*` or `large-prop-engine-*` (the model is a jet).

The towed banner cloth uses `updatePlaneBannerFlap` (per-vertex sine wave
travelling along the X axis). Banner messages come from `BANNER_MESSAGES`.

## When changing layout

- "Front" side of island = +Z. North/South/East/West correspond to ±X / ±Z;
  do not assume Y-up screen coordinates.
- The `new-island` tool creates an editable duplicate island board, not a
  cell object. It keeps its own logical board coordinates so normal tools keep
  using `setCell()`, while the island group handles X/Y/Z positioning and Y
  rotation through the gizmo. Do not expose scale for island-board transforms.
- New editable islands should not seed every default grass cell through
  `setCell()`. Keep default grass virtual, add one pickable default-surface
  mesh for the board, and materialize sparse per-cell meshes only after the
  user edits a cell.
- Duplicate island undersides use static voxel lift engines ported from
  `voxel_lift_engine.html`: propellers face downward and the thrust/plume/glow
  system remains off. Do not register these with `islandRocketFlames` or
  `islandRocketEngines`.
- For duplicate-island lift engines, the engine wrapper rotates local axes
  downward. Keep propeller local `X`/`Y` offsets at `0` so it stays centred on
  the visible lift shaft; use local `Z` (currently
  `EDITABLE_ISLAND_PROP_LOCAL_Z = -2.84`) for the lower shaft mount, and keep
  the short non-spinning spindle sleeve at `EDITABLE_ISLAND_PROP_SPINDLE_LINK_Z`
  so the propeller visibly connects to the shaft. Keep the legacy large outer
  hub cap and old two-cube hub blocks behind opt-in flags; the default propeller
  should not show block lumps on top of the shader/blur disc. High-RPM
  readability comes from the shared dark shader blur/strobe disc, while the
  voxel blade groups are a startup/slow-spin visual.
- Duplicate island lift engines are island attachments, not board cells.
  Persist their `engines` state on the island record, stamp engine meshes with
  `editableIslandEngineId` for raycast selection, and tick their propellers from
  the central animation loop.
- Mooring cables are point-to-point world decorations, not board cells. Store
  only anchor records in `moorings` (`scope: home|island`, optional
  `islandId`, and local `{x,y,z}`), rebuild their TubeGeometry under the
  non-pickable `mooringGroup`, and include them in undo/export/save state. When
  placing a cable, raycast exact surface points rather than `pickTile()` so
  underside picks work, and reject routes that pass through registered
  propeller, jet engine, or rocket plume hazard spheres.
- Mooring anchors are tied to the current board/island surface topology. Clear
  them with `clearMooringCables()` on home-grid changes, starter-scene resets,
  and demo paths that replace islands; imports can then restore valid saved
  cables with `replaceMooringCables()` after islands have been recreated.
- Number duplicate-island engine slots around the island. Slots 1 and 3 spin
  clockwise; slots 2 and 4 spin anticlockwise, so diagonal props match while
  adjacent props counter-rotate.
- Duplicate island bases should reuse the home-island greeble layers:
  `addIslandUtilityUnderside()` for underside pipes/cables/boxes and
  `addIslandEdgeDressing()` for grassy/dirt/rock edge chunks.
- Any new edge dressing must be added inside `addIslandEdgeDressing()` (per
  the existing per-edge loop with `cellRand` noise) so it stays consistent
  across all four sides.
- Anything anchored to the island that animates must be ticked from the
  central animation loop (call sites near `updateCropDuster(dt)` in
  `renderer.setAnimationLoop(animate)`).
- Duplicate islands use LOD: selected/near islands show full base/content,
  mid/far islands show cheap proxy slabs, and hidden islands skip content,
  underside detail, and engine propeller ticks. Preserve this before adding
  new per-island animation or decoration.

## Validation

After island/plane changes:
- `node tools/check.js`
- Visually check at default 8×8 grid and after toggling to 20×20 — sizes
  rebuild the island.
- Confirm planes fly behind the island, banner stays readable against the
  sky, and engine sound (if positional audio active) pans correctly L↔R as
  the plane crosses the camera.


## Mooring "Connect" cables — styles + interaction

- The infra tool is labelled **"Connect"** (id stays `mooring`, `t.mooring`).
- Each placed cable carries a `style` in `MOORING_STYLES`
  (`14-editable-islands-moorings.js`): power (amber), water (blue), waste
  (green), data (purple), mooring (default dark). `style` is normalized
  (`normalizeMooringStyleId`), persisted via `serializeMooringCables`, and
  drives the tube material (`mooringStyleMaterial`). Change it with the global
  `setMooringCableStyle(id, style)` (rebuilds + saveState).
- Cables stay `noPointerPick` for the placement raycast. `36-mooring-interaction.js`
  runs its **own** raycast against `mooringGroup` (only while the Select tool is
  active): hover swaps the cable's meshes to `mooringHoverMaterial` (blue);
  a click opens a radial (`.radial-menu.mooring-radial`, reuses radial CSS) to
  pick the style. While that radial is open a full-screen
  `.mooring-radial-backdrop` (z 45, below the buttons at z 46) `preventDefault`+
  `stopPropagation`s every pointer/wheel event and closes on outside click, so
  canvas pan/orbit cannot fire and the type buttons stay clickable. (The menu
  container is `pointer-events:none`, so without the backdrop a miss between
  buttons falls through to the canvas and pans.) Verify pickability with 3D math (project tube vertices →
  raycast `mooringGroup`), not screenshots.