The Infinite Aquarium

The Context

The Infinite Aquarium is the proof-of-concept application for multiplayer-fabric: a social, UGC bioluminescent ocean where players design jellyfish and release them into a shared neon sea built from other players’ creations. Comparable positioned titles: VRChat, Roblox, s&box.

The aquarium exercises every platform primitive in a single coherent demo: zone streaming, content-addressed asset delivery, ReBAC permissions, WebTransport/WebSocket transport, entity interest management, and RECTGTN planning. It is also the first concrete instance of the virtual creator market product (20260421-product-virtual-creator-market.md): a creator’s zone is their booth, their jellyfish are their products.

The Problem Statement

multiplayer-fabric has no reference application. Without one, it is impossible to verify that the infrastructure primitives compose correctly end-to-end, or to demonstrate the platform to creators and operators. The aquarium is the smallest application that exercises all of them in combination.

Describe how your proposal will work with code, pseudo-code, mock-ups, or diagrams

Demo scope (two-hour target)

Fetch a player-uploaded jellyfish asset from Uro by hash, instance it inside the XR grid scene, and have it visible in VR.

  1. jellyfish_asset_loader.gd calls GET /shards/:id/assets to resolve the zone asset manifest and download the baked_url for the jellyfish Godot scene.
  2. The loaded scene is instanced into the existing xr-grid scene via CMD_INSTANCE_ASSET.
  3. Player sees the UGC jellyfish appear in VR.
  4. Jellyfish movement driven by JellygridSwarm::tick() reading the current RECTGTN plan action.

Pass condition: jellyfish appears in the scene, visible to the player in VR, with another player able to see it simultaneously.

Jellyfish creator workflow

The asset format is a Godot scene. No external DCC tools required.

  1. Design with CSG nodes (bell body, tentacle sweeps) in the Godot editor or an in-world editor scene.
  2. Bake CSG to a static mesh (CSGShape3D.bake_mesh()).
  3. Save the baked mesh scene to Uro — the content-addressed store assigns a chunk hash and baked_url.

The baked scene is the canonical asset; clients instance it directly at runtime. The chunk hash is stable across uploads of identical geometry, so repeat downloads cost no bandwidth.

Zone infrastructure

The Abyss is a persistent, zone-sharded ocean:

  • Hilbert-coded zone boundaries for seamless cross-zone movement
  • Distributed simulation via multiplayer-fabric — each zone is a separate server process sharing entity state
  • Area of Interest bands so players only receive data for nearby jellyfish
  • Zone crossings are seamless; MIGRATION_HEADROOM = 400 absorbs swarm spikes
  • Performance target: 511+ jellyfish across a 3-zone loop without data loss

Zone infrastructure is implemented. See 20260421-multiplayer-fabric-zone-architecture.md.

UGC asset pipeline

Every jellyfish is a content-addressed asset bundle in Uro. Clients fetch by chunk hash at runtime and only download jellyfish within their AOI. The manifest endpoint (GET /shards/:id/assets) resolves the full asset list in one round trip. See 20260421-content-addressed-asset-delivery.md and 20260421-zone-asset-manifest.md.

RECTGTN behaviour

Each jellyfish species has a JSON-LD RECTGTN domain loaded at zone startup. The zone server runs tw_seek_plan() on domain + entity state to produce a behaviour plan stored in the CDN. Jellyfish movement in JellygridSwarm::tick() reads the current action from the plan rather than a hard-coded phase table. See 20260421-rectgtn-jellyfish-behavior.md.

Implementation status

Component Status Notes
Zone networking Working fabric_mmog_zone.cpp
Entity migration Working SCENARIO_JELLYFISH_ZONE_CROSSING
Jellyfish creator In scope CSG design → bake mesh → save Godot scene → Uro
Asset streaming In progress jellyfish_asset_loader.gd → GET /shards/:id/assets → FabricMMOGAsset
Zone console In progress multiplayer-fabric-zone-console — Elixir TUI (ExRatatui), auth + shard list via Uro REST
VR interface Testing xr-grid project
ReBAC permissions Working Uro.Acl — CAN_ENTER and CAN_INSTANCE at zone join and slot allocation
Swarm physics In scope jellygrid_swarm_sim.hpp — pure C++, no sandbox
Current simulation In scope jellygrid_current_sim.hpp — pure C++, no sandbox
RECTGTN planning In scope tw_planner.hpp standalone headers in fabric_mmog_zone.cpp; plans stored in CDN
Behavior scripts Tombstoned godot-sandbox / RISC-V ELF guest — standalone headers used instead
Pulse waveform Tombstoned dropped from asset bundle
Remix system Tombstoned clone + fork provenance chain
Moderation layer Tombstoned Uro ACL + operator tombstone endpoint
Environmental FX Tombstoned currents, rip events, bloom dynamics

The Benefits

The aquarium is the smallest application that exercises every platform primitive end-to-end. If the demo passes, the infrastructure composes correctly. If any primitive fails, the failure is immediately visible in a concrete scenario rather than an abstract test.

The Downsides

A bioluminescent jellyfish ocean is a narrow theme. Operators evaluating multiplayer-fabric for other applications (e.g. avatar showrooms, board games) must extrapolate from the aquarium. A more neutral demo (empty room with a moving cube) would be less compelling and exercise fewer primitives.

The Road Not Taken

A tag game (one chaser, rest flee across zone boundaries) would stress-test real-time position sync and zone handoff without touching asset delivery or ReBAC. It validates the engine but not the product. The aquarium validates both.

The Infrequent Use Case

A zone with no uploaded jellyfish (new operator, empty ocean) still passes the two-hour demo if the player’s own jellyfish appears after upload. The shared-ocean property is a second milestone, not a prerequisite.

In Core and Done by Us

  • multiplayer-fabric-godot/modules/multiplayer_fabric_mmog/ — zone server, swarm sim, current sim, RECTGTN integration
  • multiplayer-fabric-godot/modules/multiplayer_fabric_mmog/jellyfish_asset_loader.gd — asset manifest → CDN fetch → scene instance
  • assets/domains/jellyfish_common.jsonld, jellyfish_bioluminescent.jsonld — RECTGTN species domains
  • multiplayer-fabric-zone-backend — GET /shards/:id/assets, ReBAC enforcement, Uro asset storage
  • multiplayer-fabric-zone-console — operator TUI for zone management

Status

Status: In Progress

Decision Makers

  • iFire

Tags

  • Aquarium, PoC, UGC, Jellyfish, VR, Demo, Product, CreatorMarket

Further Reading

  1. 20260421-product-virtual-creator-market.md — product strategy; booth = zone
  2. 20260421-multiplayer-fabric-zone-architecture.md — zone infrastructure
  3. 20260421-rectgtn-jellyfish-behavior.md — RECTGTN planning for jellyfish
  4. 20260421-zone-asset-manifest.md — GET /shards/:id/assets
  5. 20260421-content-addressed-asset-delivery.md — casync/Uro asset pipeline
  6. 20260421-rebac-zone-server-enforcement.md — CAN_ENTER and CAN_INSTANCE