MoneyField

Renderer-agnostic collectible-money field: spawns piles of coins and cash that magnet to the player and fly to the HUD corner, banking their value.

What it does

The MoneyFieldSystem drives a pure MoneyFieldSim (one per kind: GoldCoin and MoneyStack) that owns each pickup's transform and lifecycle in typed arrays — piles spawn on a timer inside the placement area, resting coins inside magnetRadius of the player suck toward it, then streak to the live top-left screen corner while shrinking, and on arrival their value is banked. It is renderer-agnostic: it never imports an engine and instead drives the adapter's thin-instance field API (loadThinField / setThinFieldInstances / disposeThinField) plus screenToWorldPoint, so the GPU draws thousands of pickups in one call per kind and the same code runs under the Babylon and Three adapters. It reads the player-tagged entity's MeshPrimitive for position and the ArcCamera handle to re-project the HUD corner each frame. When money is collected it emits MoneyFieldEvents.CHANGED with the running total and the frame's delta.

Use it in a scene

A scene is just data — a list of entities, each with its components. At startup the SceneLoader turns this JSON into a live world; edit the file and reload to rebuild it.

Fastest path

bjs download scene MoneyField

Pulls this exact scene into your project and runs it — no copy-paste. Add --all to grab the components and assets it needs too.

Or build it from scratch with the bjs CLI:

1Scaffold a project
```
npm create @babylonjsmarket/arcade@latest my-game
```
World, renderer, and dev server — ready to run.
2Install dependencies
```
cd my-game && npm install
```
3Add MoneyField
```
bjs download MoneyField
```
Copies its source into src/ so the scene resolves.
First time? Run bjs login once.
4Paste the scene into src/scenes/arcade-room.ts and run
```
npm run dev
```
SceneLoader builds the world from the JSON; reload to rebuild.

JSON

{
  "entities": {
    "Camera": {
      "components": {
        "ArcCamera": { "target": "Player", "distance": 42, "alpha": -1.5708, "beta": 0.55 }
      }
    },
    "Player": {
      "tags": ["player"],
      "components": {
        "MeshPrimitive": {
          "primitive": "capsule",
          "radius": 0.5,
          "height": 1.6,
          "position": [0, 0.8, 0]
        }
      }
    },
    "World": {
      "components": {
        "MoneyField": {
          "src": "/shooter/money.glb",
          "capacityPerKind": 1200,
          "pileInterval": 4,
          "maxPiles": 6,
          "coinsPerPile": 40,
          "stacksPerPile": 36,
          "magnetRadius": 3,
          "spinSpeed": 0
        }
      }
    }
  }
}

Props

src (string, default /shooter/money.glb) — GLB holding the GoldCoin and MoneyStack nodes.
capacityPerKind (number, default 1200) — pooled thin-instance ceiling per kind.
pileInterval (number, default 3) — seconds between automatic pile spawns.
maxPiles (number, default 8) — soft cap on piles' worth of coins alive at once.
coinsPerPile (number, default 36) — GoldCoins scattered per pile.
stacksPerPile (number, default 24) — MoneyStacks scattered per pile.
pileRadius (number, default 1.8) — scatter-disc radius of a pile (world units).
magnetRadius (number, default 3) — player pickup magnet radius (world units).
coinSize (number, default 0.5) — largest world dimension of a GoldCoin; the renderer normalizes to this.
stackSize (number, default 0.9) — largest world dimension of a MoneyStack.
coinRestY (number, default 0.3) — resting Y of coins.
stackRestY (number, default 0.45) — resting Y of stacks.
suckSeconds (number, default 0.22) — duration of the suck-to-player phase.
cornerSeconds (number, default 0.5) — duration of the player→corner streak phase.
spinSpeed (number, default 3) — coin spin rate (rad/s) about Y.
placementHalf (number, default 16) — half-extent of the square placement area.
clearCenterRadius (number, default 6) — keep piles this far from arena centre (player spawn).
avoid ([x, z, r][], default four corner discs) — no-spawn discs.
coinValue (number, default 1) — money awarded per GoldCoin.
stackValue (number, default 25) — money awarded per MoneyStack.
seed (number, default 0) — fixed layout seed; 0 uses Math.random.

Events

emits MoneyFieldEvents.CHANGED ('money.changed') — { total, delta } whenever coins are banked this frame.

Dependencies

MeshPrimitive — the player-tagged entity's component supplies the position coins magnet toward (its mesh may be visible:false; the System reads the component, not the mesh). ArcCamera — its live camera handle is re-projected each frame so the corner target stays pinned to the HUD as the view pans.

Notes

The pickups have no collider — enemies and the player walk straight through a pile; only the magnet radius collects them.
Coins spin (the classic pickup tell); stacks keep a static varied yaw — set spinSpeed to 0 to freeze coin spin too, as the example scene does.
A first pile spawns immediately on load so there's money on the field at spawn; the timer takes over afterward.
Only live slots are packed and drawn each frame, so the pooled (free) capacity costs the GPU nothing.