# v2: borrowed tech (gold dust)

Other people's work we take from, deduplicated and grouped by area. Add to this list whenever
something is found. Index: `agents/world-format-v2.md`. Licence verdicts that decide what we
may ship live in the area docs (`world-and-content.md`, `characters.md`); this list only notes
them.

## Engine model, modding, sandbox
- **Source / Hammer entity I/O** (Valve; ModDB "Hammer Logic Tutorial"): outputs to inputs with
  delay and param; `logic_relay`, `logic_case`, `logic_branch`, `math_counter`. Copied nearly
  verbatim.
- **Valve Developer Community:** `Surface_properties`, `Gib`, `Constraint`, `Response`,
  `Choreography_creation`, `Env_sound`, `Nodegraph`, `DEM_Format`: the reference for the Source
  checklist (`missions-and-forge.md`).
- **s&box** (Facepunch, Source 2, C#, shipped Apr 2026): code hotloads to every client in the
  session in milliseconds. The bar for our mod dev loop.
- **Garry's Mod addon layout** (wiki.facepunch.com): folder per content type (entities/,
  weapons/, stools/, gamemodes/); a gamemode is a mod only active while played. Mirror it
  for mod packages (always-on tools vs opt-in rulesets and missions).
- **Wasmtime + Extism:** capability sandbox with zero ambient authority; fuel metering for
  deterministic mod CPU budgets, epoch interruption for timeouts. **MicroPython (WASM port)** or
  **Starlark** for the Python-flavoured tier; Pyodide is too heavy (200+ MB).
- **hecs** (minimal SoA ECS) vs **bevy_ecs** (fuller, has a scheduler): the old lean was hecs;
  the port plan now uses custom sparse sets with hecs as prior art (`simulation.md`).
- **Breath of the Wild's "chemistry engine"** (Nintendo, GDC 2017 "Breaking Conventions"): a few
  element and material rules (fire, heat, wind, electricity, water) producing emergent play.
  The direct precedent for principle 7. **Far Cry 2:** fire spreading through dry grass by wind.

## Destruction and lighting
- **Teardown** (Dennis Gustafsson, blog.voxagon.se; "Raytracing Voxels in Teardown and
  Beyond"): 1 byte per voxel with an 8-bit material palette, custom voxel rigid-body physics,
  traced AO and shadows only. The destruction and lighting reference.
- **Voxolith** (voxolith.github.io, MIT): WebGPU/WGSL raymarched voxel world with a two-level
  brick index and demolition. Study its brick format for destructible buildings.
- **Rapier voxel colliders** (dimforge, v0.25.0 Apr 2025): `ColliderBuilder::voxels`,
  `voxelized_mesh`. Experimental, but the primitive destruction builds on.
- **Lumen software mode** (Epic): SDF / voxel scene representation for bounce light without RT
  hardware; the model for GI beyond Teardown's scope.

## Rendering
- **three.js TRAANode + TSL:** built-in temporal AA; TSL compiles one graph to GLSL and WGSL.
- **pmndrs/upscaler** (MIT; FSR 2/3 as TSL nodes; small, check Safari and Firefox) and
  **three-taau** (ours, `/home/gabriel/render/web/src/taau/`, FSR2-class TAAU for WebGL2).
- **render.gabrielpenman.com** (ours, `/home/gabriel/render/web/src/effects/`, and its
  sensors/, taau/ and perf/ siblings): the physical camera pipeline.
- **Dither3D** (github.com/runevision/Dither3D, MPL 2.0): port from the Shadertoy/Godot versions.
- **wgpu** (one Rust renderer for browser and native, deferred); **Steamworks + Tauri/Electron**
  (the quick Steam wrap).

## Capture and asset generation
- **PGSR / 2DGS / SuGaR** (arXiv 2406.06521, 2403.17888): surface-aligned splats to meshes;
  PGSR's multi-view photometric consistency loss is our rebuild-and-compare gate (reimplemented;
  the originals are non-commercial) and works for pipeline facades as well as splats.
- **Relightable splats: DR-GS, MaterialClusterGS, GS-2M** (arXiv 2026): splat to PBR material
  decomposition. Research-stage, no production tool; an R&D dependency of the splat loop.
- **Asset generation:** TRELLIS.2 (microsoft, MIT; nvdiffrast non-commercial); SPAR3D/SF3D (fast
  placeholders, Stability community licence); SAM 3D Objects; MatFuse, StableMaterials, Material
  Palette, MatE (materials); CoACD (hulls); meshoptimizer, xatlas, Instant Meshes (LOD, UV,
  remesh). Excluded: Hunyuan3D (licence excludes the UK).
- **Mineways:** Minecraft to 3D model export at 1 block = 1 m (our scale). Untested pilot route
  for community builds.

## Environment and water
- **Environment:** TICON-4 tide constants (seanoe.org, CC-BY); NOAA SP98 / XTide harmonics notes
  (flaterco.com); ADMIRALTY UK Tidal API (validation); Open-Meteo (real weather, ERA5 climate
  tables); pmndrs/sky (Hillaire sky in TSL; fallbacks SebH-TSL-Sky, webgpu-sky-atmosphere);
  Nubis clouds in three.js (demo-2025-raymarch-clouds, `webgpu_volume_cloud`); three.js
  `webgpu_compute_particles_rain` and ektogamat/threejs-conference (TSL rain and wet streets);
  Arkham Origins deformable snow (GDC 2014); Ghost of Tsushima grass and wind (GDC); Lagarde's
  "Water drop" wet-surface series; SunCalc (BSD); Tyne Kittiwakes (tynekittiwakes.org.uk).
- **FFT ocean on WebGPU:** Poseidon (three.js WebGPURenderer/TSL, cascaded compute IFFT),
  WebTide (Babylon), ocean-fft-wgsl. Proof the Tyne/sea surface runs in-browser now.
- **Unreal Buoyancy Component:** pontoon sample points per mesh, per-point force and torque. The
  buoyancy model to copy onto Rapier.
- **Shallow water on WebGPU:** lisyarus/webgpu-shallow-water (virtual pipes; his blog
  "Simulating water over terrain"), jeantimex/webgpu-water, deluge-flood-sim (real-terrain
  floods). Our local water and street floods. The tidal Tyne needs a bespoke tide-driven
  boundary on top; no prior art found.
- **Particle fluids:** WebGPU-Ocean (MLS-MPM, 100-300k particles), jeantimex/fluid (SPH, FLIP),
  Matthias Müller's Ten Minute Physics FLIP. For splash, spray and waterfall detail only.

## Physics and vehicles
- **Space Engineers** (GDC 2023, Hloušek, "Predicted Physics Based Multiplayer"): server
  authority, client-predicted grids, delta-state replication. The verified reference for moving
  vehicle frames.
- **GTA V vehicle damage:** rigid parts + breakable joints + a deform shader, no soft body. Our
  baseline.
- **Vehicles:** Rapier `ray_cast_vehicle_controller.rs` (Bullet port; reuse casting and
  suspension only); Jolt Physics `WheeledVehicleController` (MIT; drivetrain and differentials
  to port); Project Chrono::Vehicle tyre models (BSD-3; TMsimple as the cheap real tyre); Marco
  Monster "Car Physics for Games"; Edy's Pacejka '94 parameter guide; Rocket League (GDC 2018,
  Cone: input-decay prediction between authoritative corrections); Rigs of Rods (GPLv3, study
  only: an inspectable node-beam soft-body solver if the player car ever goes BeamNG-style);
  Kenney Car Kit (CC0).

## Characters and animation
- **ashleve/ActiveRagdoll:** open PD-controller active ragdoll, a reimplementation of what
  Euphoria (GTA IV/V) is believed to do. Port onto Rapier joint motors.
- **Active ragdoll balance** (Jan Schneider, "Balancing of Active Ragdolls in Games"):
  per-joint PID towards an animated pose, local stiffness drop on impact, foot-placement
  recovery. Biomechanics agrees: hip strategy plus stepping.
- **DeepMimic / AMP / ASE** (Peng et al.; nv-tlabs/ASE has pretrained checkpoints, NVIDIA NC):
  learned physics controllers, trained offline. **PFNN** (theorangeduck.com): few-MB,
  millisecond kinematic controller.
- **Characters:** MPFB2/MakeHuman assets (CC0), VRM 1.0 + three-vrm (MIT), Microsoft Rocketbox
  (MIT; 115 rigged avatars with visemes/FACS/ARKit, clothes fused, good for crowds), Kenney
  (CC0), 100STYLE, CMU mocap, Mixamo (baked-in only), orangeduck/Motion-Matching, GarmentCode,
  AIpparel, ChatGarment, Robust Skin Weights Transfer, StdGEN, UniRig, MagicArticulate, Rhubarb
  Lip Sync, TalkingHead/HeadAudio, wawa-lipsync, Audio2Face-3D SDK, three.ez instanced-mesh,
  gltf-transform, Falconsai/Marqo NSFW detectors, Roblox layered clothing (cages, idea only).
- **Cutie-Roto** (open-source AI rotoscoping masks) and EbSynth-style style propagation for
  cutscenes; flickers on long shots.

## NPCs
Crowds in Hitman: Absolution (Fauerby, GDC 2012); Planet Coaster flow-field crowds; Census,
Watch Dogs: Legion (GDC); GTA `popcycle.dat`; Splinter Cell: Blacklist perception (Game AI Pro 2
ch. 28); navcat, recast-navigation-js, rerecast, landmass, dodgy_2d (ORCA), polyanya; flow-field
tiles (Emerson, Game AI Pro); F.E.A.R. GOAP (Orkin); utility AI (Dave Mark); IDM and MOBIL; cell
transmission model (Daganzo); Bus Open Data Service GTFS; Ofcom's GenAI and chatbots letter;
NVIDIA ACE / inZOI.

## Missions, worlds, claims
- **GTA Online heists / Roblox `ReserveServerAsync` + `TeleportToPrivateServer`:** shared world
  for free roam and prep, reserved instance for the finale, return after.
- **Build The Earth / Second Life land / GTA Online properties:** team territories, leased
  parcels, instanced interiors. Three claim models to pick from.

## Netcode and persistence
- **GGPO / rollback netcode:** per-frame state checksums between peers pinpoint the diverging
  frame. **Overwatch** (GDC 2017, Ford): ECS netcode where only a few systems take part in
  rollback. **EVE grids:** adaptive spatial cells bound what syncs. (Rocket League: under
  vehicles.)
- **Netcode:** Gaffer on Games "State Synchronization" and networked physics; Quake 3 delta
  compression; netcode.io connect tokens; geckos.io (node-datachannel); Colyseus 0.18 (schema
  deltas, server-authoritative only); Photon Fusion shared mode (per-object state authority);
  caniuse WebTransport; Hetzner Cloud API pricing.
- **Persistence:** Litestream (SQLite to object storage); Hetzner Object Storage; CoreProtect
  (rollback by user, time, radius); ProfileService (session-locked player data); Loro (Rust
  CRDT); Rust (the game) monthly wipes; Second Life region rollback.

## Audio
Steam Audio (Apache 2.0; HRTF, occlusion, baked reverb; WASM experimental); Firewheel +
firewheel-web-audio (Rust audio graph in an AudioWorklet); Resonance Audio web SDK (archived Apr
2026, room-model reference only); Paul Adenot's Web Audio performance notes
(padenot.github.io/web-audio-perf); Wwise rooms and portals; Valve soundscapes and DSP presets;
Ruskin GDC 2012 "Dynamic Dialog" (Response Rules); engine sound: Jonas-Hack granular engine
audio, VehicleNoiseSynthesizer, DasEtwas/enginesound (Rust), Antonio-R1/engine-sound-generator
(Web Audio).

## Forge UX
Roblox Assistant planning mode and Roblox Studio MCP server (create.roblox.com docs); three.js
TransformControls; Dreams and LittleBigPlanet (microchips, thermometer); Halo Forge (instant edit
toggle); Unreal Blueprints (wire pulses); gmod FPP and Advanced Duplicator 2 (per-author undo,
paste checks); UEFN device wiring (unverified details).

## Community, content policy, law
- **Community:** CDPA s62; E-Commerce Regs 2002 reg 19; ICO children and ISS consent; GitHub ToS
  (13+); Steam Subscriber Agreement (Workshop licence); Roblox DevEx; OSM Contributor Terms;
  Wikipedia licensing-on-submit.
- **Content policy:** PEGI label meanings (pegi.info); Steam Content Survey (partner docs); IARC
  storefront list; Roblox content maturity labels; Online Safety Act s.55 and s.62
  (legislation.gov.uk).

## Ruled out
- **Google photorealistic 3D tiles:** their licence forbids caching and baking.
- **Hunyuan3D:** licence excludes the UK. Other never-use licences: `characters.md`,
  `world-and-content.md`.