# Sports Framework — Expansion Plan What you already have is not a hockey demo with spare parts. It is a **character + physics + intent** stack that happens to be wired as ice hockey. The goal of this document is to name the seams honestly, list what still has to become *sport-agnostic*, and outline what would remain as **sport packs** so the same building blocks can ship football, basketball, soccer, fighting, racing-on-foot, and contact sports without forking the engine. This is complementary to [ROADMAP.md](ROADMAP.md) (hockey product depth) and [README.md](README.md) (current architecture). Here the question is: > What would it take for *this package* to be the framework under *any* sport game? --- ## 1. The thesis A general sports framework is not “one locomotion model that does everything.” It is a **small set of contracts** plus **pluggable sport modules**: | Layer | Owns | Sport-specific? | |-------|------|-----------------| | **Body stack** | skeleton, mesh, skinning, body style, ragdoll, proxy | mostly shared | | **Equipment stack** | gear builders, sockets, coverage, colliders | shared builders; sport kits | | **Motion stack** | pose buffer, crossfade, IK, override layers, clips later | shared runtime; sport poses | | **Locomotion** | intent → velocity → footing | **one model per surface/gait family** | | **Impact** | did hit / what kind / severity / handoff limp↔driven | shared core; sport rules | | **Object play** | ball/puck possession, tool use, goals | sport packs | | **AI** | roles, intent writers, formation | shared brain shell; sport tactics | | **Arena** | bounds, surfaces, markings, static colliders | sport packs | | **Rules / match** | clock, score, phases, sanctions | sport packs | | **Studio / harness** | shot sheets, drills, capture, regression | shared tooling; sport catalogs | Hockey already forces the hard problems (anisotropic friction, limb-level contact, tool-in-hand IK, pure sim in `shared/`). That is why a framework *can* fall out of this — but only if hockey stops being the type system. --- ## 2. What you already have (framework seeds) These are reusable with little or no redesign. ### 2.1 Character body pipeline - **23-bone A-pose skeleton** (`skeleton.js`) with regions, bone radii, segment graph - **Procedural lofted body** (`body.js`) + **distance-field skinning** (`skinning.js`) - **Body style morphs** mass / muscle / fat (`bodyStyle.js`) — already sport-neutral - **Materials / team tints** (`materials.js`) — team identity, not hockey identity ### 2.2 Equipment geometry kit - **`gearMesh.js`**: `loft`, `carvedShell`, `tube` — sport-agnostic mesh grammar - **Socket + skinned cloth pattern** (hard shells on bones, cloth skinned with `aPart`/`aT`) - **`hideCoveredBody`** coverage masks so kit replaces flesh Hockey gear (`skaterGear`, `goalieGear`, `stick`) is content *on top of* that grammar. ### 2.3 Animation runtime - **Pose buffer + state crossfade + override layers** (`skateAnimator.js`) - **Two-bone analytic IK** (legs; goalie legs; stick grip reach partially) - **Override layers that multiply spine** while replacing arms (stickwork) — correct pattern for “keep locomoting while acting” - **Animator does not own movement** — sim/proxy own position (critical for all sports) ### 2.4 Physics character loop - **Proxy capsule for standing presence** + **kinematic ragdoll for pose/hits** - **Limp handoff** with root re-expression so get-up does not double-apply slide - **Limb-pair hit classification** from posed capsules (`hits.js`) — the right separation of *did hit* vs *what hit* - **Collision layers / tags** (`bridge.js`) — extensible KIND system ### 2.5 Intent seam - **`applyIntent`** clamped entry (`skaterSim.js`) — controller, AI, and netcode all write the same shape - **Camera-relative stick** (`input.js`) — gamepad/keyboard already abstracted ### 2.6 Pure sim island - **`shared/`** free of three.js, headless-testable, server-ready - **Headless test culture** (pose, AI, physics, hits) + **capture / img2mesh** tools ### 2.7 Studio / reference loop (seed) - **Character studio** (`character.html` + `img2mesh`) with pose presets, fixed views, shot sheets, optional live drill (puck machine) - Pattern: *author → capture sheet → drop refs → re-capture → diff by eye (or later pixel)* --- ## 3. What is still hockey-shaped (must peel off) These block “any sport” until they become interfaces + plugins. | Hardcoded today | Why it blocks generality | |-----------------|---------------------------| | `shared/skaterSim.js` is *the* locomotion | Running, plant-and-cut, swim, bike, skate all need different footing models | | `shared/rink.js` is the arena | Rect + corner radius is not a pitch, court, ring, or track | | `shared/ai.js` puck roles + rink half | Roles are puck/carrier/chaser; no ball/goal/zone abstraction | | `possession.js` + stick blade | Magnetism dial is excellent, but assume blade + cylinder puck | | `stick.js` grip-space tool | Need generic **held tool / ball socket / two-hand implement** | | `hits.js` CAN_DELIVER / ice thresholds | Sport contact rules differ (tackle vs check vs foul vs strike) | | `goalie` as special entity type | “Keeper” should be a role/locomotion profile, not only a hockey class | | `match.js` / `shootout.js` | Match loop is sport session; not a generic phase machine | | `input.js` Skill Stick / hockey stop | Sport action maps differ; need bindable action sets | | Pose catalogs only skate / stick / goalie | Need gait families + sport action libraries | | Physics world assumes ice plane + boards | Surfaces (friction, bounce), goals, posts, glass, hoops, cages | | Package name / scripts assume hockey MVP | Cosmetics; real issue is import graph coupling | --- ## 4. Target architecture ``` packages/ (or src/ layered) core/ math, rng, time, determinism helpers body/ skeleton, body loft, skinning, bodyStyle, ragdoll, proxy gear/ loft/shell/tube builders, socket attach, coverage anim/ pose buffer, blend, IK solvers, layer stack, clip hooks locomotion/ interface + models: skate, run, plant, crouch-shuffle, … impact/ contact resolution, limb pairs, severity curves, handoff object/ free bodies, attachment/magnetism, tools, projectiles arena/ surfaces, bounds, static colliders, markings API brain/ intent writer, roles, blackboard, formation helpers match/ phase machine, clock, score, events (sport-agnostic shell) input/ device → action set → intent render/ materials, camera presets, arena mesh helpers studio/ pose/view catalogs, capture API, ref sheets, drills harness/ headless scenarios, golden metrics, capture regression sports/ hockey/ rink, skate loco, stick, puck, check rules, shootout, AI (future packs) football/ basketball/ soccer/ fighting/ (Ludus-adjacent — already half-solved) … ``` **Rule:** a sport pack may depend on the framework. The framework must not import a sport pack. Hockey becomes the first pack that proves the contracts. Ludus fighting is the second pack if contact + minigame reuse is the priority (see ROADMAP fighting note). --- ## 5. Contracts to extract (the real work) ### 5.1 Locomotion model (`ILocomotion`) **Have:** carve/glide blade model + intent fields (`ix, iz, sprint, brake`). **Need:** ``` createState(spawn, profile) → state applyIntent(state, msg) // clamped, never trusts client step(state, dt, env) // env: surface, contacts, clamps readout(state) → { speed, gaitPhase, bank, plantL, plantR, … } ``` **Locomotion families to support eventually:** | Family | Examples | Key physics | |--------|----------|-------------| | **Blade / edge** | ice hockey, figure, speed skate | anisotropic friction, carve | | **Run plant** | soccer, basketball, football | foot plant, cut friction, acceleration | | **Crouch / shuffle** | goalies, catchers, linemen | lateral step without full gait | | **Contact-limited** | rugby ruck, board pin | reduced mobility under constraint | | **Aerial / jump** | basketball, volleyball, headers | ballistic + land recovery | | **Vehicle-assisted** | cycling, wheelchair, luge | separate later; not v1 | **Left to build:** - Shared `env` (surface µ, max slope, out-of-bounds clamp hooks) - Foot plant bookkeeping for run gaits (world-planted feet vs mover-local skate feet) - Profile data (top speed, accel, turn radius by sport / position / fatigue) - Unit tests per model mirroring `test/skaterSim.mjs` ### 5.2 Footing & IK policy **Have:** mover-local foot targets for skating; world-height leg IK for goalie pads. **Need:** - **`IFootPolicy`**: glide | plant | pivot | kick | slide - World-space plant IK for walk/run (Ludus-style), without regressing skate glide - Arm IK generic: **two-hand implement**, **one-hand hold**, **catch**, **block** - Spine/look-at IK for tracking ball / opponent (broadcast + AI readability) - Hand-to-object solve that reports *reach error* (you already see this on stick grip) **Left to build:** - Unified IK module (two-bone + simple FABRIK/pole vectors), shared by sports - Constraint priorities (feet > implement > look) so layers don’t fight - Authoring helpers: target sockets in mover-local vs world ### 5.3 Pose / animation system generalization **Have:** states + stick override layers + goalie stance set. **Need:** - **Locomotion graph** (idle, walk, run, sprint, cut, stop, jump, land, fall, getup) - **Action layers** (shoot, pass, tackle, catch, block, celebrate) with blend masks - **Clip adapter** interface early — procedural remains default; mocap/clips plug in without rewriting sports (ROADMAP already names motion matching as the ceiling) - Shared **get-up / knockdown / stagger** presentation states (physics-driven entry) **Left to build:** - Pose catalog format (JSON or pure JS) keyed by sport + role - Layer stack API (replace vs multiply vs additive per bone set) - Phase drivers from locomotion readout (gait phase, effort, bank) - Optional motion-match slot (even if empty) so content pipeline isn’t a rewrite later ### 5.4 Equipment framework **Have:** builders + hockey kits + stick as special tool. **Need:** ``` EquipmentDef { id, sockets[], skinnedParts[], rigidParts[], colliders[], coverage[], massAdd, tags[] } ToolDef extends Equipment // stick, bat, racket, gloves-as-weapons WearableDef extends Equipment // helmet, pads, jersey, cleats ``` **Left to build:** - Data-driven attach (bone name + local TRS + optional skin weights) - Size from physique (you already scale gear off `physique` — generalize) - Collider generation from mesh bounds or authored capsules - Damage/armor hooks by `REGION` (skeleton already has regions “from GDD”) - Asset path: procedural first, imported glTF meshes later behind same sockets - **Reference-driven iteration**: shot sheet per equipment part (front/side/3q/detail) ### 5.5 Player assembly (`createAthlete`) **Have:** `createSkater`, `createGoalie` — two assembly paths. **Need:** one factory: ``` createAthlete({ seed, bodyStyle, team, locomotion: 'skate' | 'run' | …, role: 'skater' | 'keeper' | 'striker' | …, loadout: EquipmentDef[], animProfile, impactProfile, }) ``` Roles swap locomotion, gear, AI profile, and action map — not hard forks of the character. ### 5.6 Impact / contact sports core **Have:** proxy collision + limb pair + severity tiers + limp handoff + get-up fix. **Need:** - **Impact profiles** (thresholds, limbShare, bonuses, legal deliverers) per sport - Legal / illegal contact classification as *rules callback*, not hardcoded hockey - Multi-body pile stability (proxy equilibrium already soft under pressure) - Grapple / pin / clinch states (football tackle finish, wrestling, board battle) - Strike profiles for combat sports (Ludus) reusing limb pairs + reaction curve - Surface hits (wall, boards, post) feeding same severity pipeline - Injury / fatigue hooks off region + severity (data only; presentation later) **Left to build:** - `createImpactSystem({ profile, rules })` replacing hockey-tuned `HIT` constants - Deliverer allow-lists as data - Contested body state (pinned, held, blocked) separate from limp - Harness scenarios: open ice hit, wall pin, tackle wrap, pile-up ### 5.7 Object / ball / tool play **Have:** puck body, blade collider, magnetism possession dial, release step-clear. **Need:** - Generic **`PlayObject`**: sphere / cylinder / prolate (ball types), mass, restitution - **Attachment models**: hard parent, soft magnetism, carry socket, two-hand cradle - **Release models**: impulse from tool velocity, throw arc, kick from foot bone - Contested possession (you already noted nearest-index-wins is too coarse) - Multi-object (only one puck today) **Left to build:** - `object/possession.js` parameterized (radius, catch cone, break force, magnetism) - Tool velocity sampling at release (stick already aims; generalize to foot/hand) - Interaction matrix: body part × object × surface - Sport rules for out-of-bounds / last touch (thin event layer) ### 5.8 Arena / surface system **Have:** NHL rink numbers, board outline, ice clamp, markings texture, nets. **Need:** ``` ArenaDef { bounds, // polygon or compound surfaces[], // friction, restitution, name staticColliders[], goals[] | targets[], spawns[], markings, // render only } ``` **Left to build:** - Containment for rect, rounded-rect, circle, custom polyline - Surface queries under feet (ice vs turf vs hardwood changes loco) - Goal/score volumes as triggers (net is hockey-specific geometry) - Camera volumes / broadcast rails optional metadata ### 5.9 AI brain shell **Have:** waypoint steer, personal space, board lookahead, carry/chase/support/defend via nearest-to-puck, intent-only outputs. **Need:** ``` Brain { sense(world) → facts rolePolicy(facts) → role tactic(role, facts) → goal motor(goal) → intent + actions } ``` **Left to build:** - Blackboard / facts schema (ball, goals, teammates, opponents, clock, score) - Role set as data per sport (not four hockey enums only) - Formation / spacing utilities (slots relative to ball and own goal) - Difficulty as parameter on reaction lag, aim cone, decision rate - Keeper brain as role using shuffle locomotion (generalize goalie) - Headless scenario tests: “defend lead”, “press high”, “box out” per pack Hockey AI depth (forecheck systems, etc.) stays in the hockey pack / ROADMAP. ### 5.10 Match / rules shell **Have:** `createMatch` loop, shootout phase machine, goal detection helpers. **Need:** - Generic **phase machine**: warmup → live → stoppage → restart → end - Event bus: goal, foul, out, period, possession change, hit - Score / clock / period as configurable - Restart spawns from arena + rules (faceoff, kickoff, freethrow, scrum) **Left to build:** - `match/runtime.js` with sport rules plugin - Deterministic event log (gates replay + netcode later) - Minimal HUD adapter (score/clock) sport-agnostic ### 5.11 Input / action maps **Have:** Xbox + keyboard, Skill Stick gestures, rumble on hit. **Need:** - Action set per sport (`move`, `sprint`, `primary`, `secondary`, `skillAxis`, …) - Gesture recognizers as plugins (Skill Stick shoot is one plugin) - Rebind + dual-input last-wins (keep current behavior) ### 5.12 Studio, reference sheets, training harness This is the differentiator you called out. Today it is hockey-shaped but the **loop** is correct. **Have:** - Live studio with pose/view catalogs - CLI shot sheet (`img2mesh`) - Puck machine drill for goalie - Headless tests + `capture` screenshots - `hitprobe` for contact **Need for framework-grade training harness:** | Capability | Purpose | |------------|---------| | **Subject registry** | any athlete role + loadout, not only player/goalie | | **Pose/view catalogs as data** | sport packs register entries | | **Reference slots** | `ref///_.png` side-by-side | | **Diff mode** | flip / onion-skin / histogram vs previous capture | | **Drill factory** | spawn scenario (1v1, shooting gallery, tackle pad, PK) | | **Metric probes** | blade height, foot plant error, reach error, joint limits, timing | | **Scenario packs** | headless scripts asserting metrics, not only “no NaN” | | **Optional photo-guided authoring** | import ref image as camera-aligned overlay (not auto-mesh) | | **Later: mesh-from-image assist** | silhouette / part labels → loft section hints (research; not blocking) | **Important scope note:** true **image → production mesh** (full photogrammetry / generative retopo) is a product of its own. The framework should treat **reference photos and sheets as the iteration contract**, with procedural gear remaining the authoritative runtime asset until a mesh pipeline earns its keep. **Left to build (practical order):** 1. Registry + data-driven catalogs (so new sports don’t edit `img2mesh.mjs` internals) 2. Side-by-side ref overlay in studio + CLI compare report 3. Metric HUD (contact points, IK targets, capsule overlays — debug already half there) 4. Drill API used by shootout machine, then tackle/shot drills for other packs 5. Golden metric tests (blade height style) per sport pack 6. Optional: capture matrix in CI on PR (you already have the capture tool) --- ## 6. Sport packs — what each still needs on top of the framework Once contracts exist, each sport is mostly **content + rules + AI policy**, not a new engine. ### 6.1 Ice hockey (first pack — mostly present) **Done enough:** skate loco, rink, stick, puck, checks, shootout, basic AI, goalie MVP. **Pack backlog:** see ROADMAP (full 5v5 rules, goalie depth, positional AI, possession feel). ### 6.2 Fighting / combat (highest reuse from Ludus + impact core) - Strike / block / grab action layers - Ring/cage arena - Stamina and limb disable via `REGION` - Existing fighting system port (ROADMAP already flags this) ### 6.3 Soccer - Run plant locomotion + ball foot/chest/head contacts - Large pitch arena, goals, out/throw-in/corner rules - No (or soft) limb impact; shoulder challenge profile - AI: formations, offside line fact, keeper dive (shuffle + dive loco) ### 6.4 Basketball - Run + jump + plant, ball carry/dribble magnetism variant - Court, hoop trigger, shot arc from release - Screen / box-out contact (low severity impact profile) - AI: pick-and-roll roles, spacing ### 6.5 American football / rugby - Run + explosive cut; tackle as grapple-to-limp pipeline - Field, downs/ruck rules plugin - Heavy impact profile; pile-up stability critical - AI: playbooks as scripted formations + read trees ### 6.6 Basketball-adjacent / volleyball / handball - Shared run + jump + catch/throw object model - Different arenas and score targets ### 6.7 Non-goals for v1 framework - Full vehicle sports, water sports, golf swing fidelity, licensed broadcast packages - Complete mocap library (architecture must allow it; content is separate) --- ## 7. Gap list — prioritized build order Phased so each phase ships a **usable contract** and keeps hockey working as the proving pack (strangler pattern: extract behind interfaces, re-home hockey). ### Phase 0 — Inventory & seams (days) - [ ] Draw import graph: mark `shared/*` vs sport-coupled modules - [ ] Freeze contracts in a short `docs/contracts.md` (or this file §5 as source) - [ ] Prove Box3D determinism (ROADMAP) — gates multiplayer *and* harness replay - [ ] Decide monorepo layout (`sports/hockey` vs stay single package with folders) ### Phase 1 — Athlete + gear core (1–2 weeks) - [ ] `createAthlete` + loadout list; skater/goalie become configs - [ ] EquipmentDef schema; move stick/pads to data-ish modules - [ ] Physique-driven sizing API documented - [ ] Studio subject registry reads loadouts ### Phase 2 — Locomotion interface (1–2 weeks) - [ ] Extract `ILocomotion` from `skaterSim` - [ ] Keep skate model as implementation #1 - [ ] Stub `runPlant` model good enough for a mannequin jog (even ugly) - [ ] Foot policy switch (glide vs plant) wired to animator ### Phase 3 — Anim / IK platform (2–3 weeks) - [ ] Shared IK solvers module - [ ] Layer stack API (locomotion / action / reaction / getup) - [ ] Reaction/stagger as layers driven by impact system - [ ] Clip adapter interface (null implementation OK) ### Phase 4 — Impact + object cores (2–3 weeks) - [ ] Impact profiles + rules callbacks - [ ] Generic play object + possession magnetism - [ ] Tool release sampling - [ ] Contested capture v1 ### Phase 5 — Arena + match shell (1–2 weeks) - [ ] ArenaDef; rink becomes hockey arena pack - [ ] Phase machine + event log - [ ] Score/clock/HUD adapters ### Phase 6 — Brain shell (2+ weeks, ongoing content) - [ ] Facts blackboard + role policy - [ ] Formation helpers - [ ] Keeper role using shared pieces - [ ] Scenario harness for AI regressions ### Phase 7 — Studio / training harness productize (parallel after Phase 1) - [ ] Data-driven pose/view catalogs - [ ] Reference overlay + capture matrix - [ ] Metric probes + golden tests - [ ] Drill factory (shooting, tackling, 1v1) - [ ] Optional ref-image camera plate ### Phase 8 — Second sport pack (proof) Pick **one** of: - **Fighting** (max reuse of impact + Ludus), or - **Soccer prototype** (max pressure on run loco + ball object) Success criterion: second sport does **not** fork `skeleton`, `ragdoll`, `gearMesh`, `hits` core, or studio capture — only pack content + profiles. --- ## 8. What “done” looks like for the framework (not for a sport) You can claim a sports framework when **all** of these are true: 1. **New athlete** = skeleton + bodyStyle + loadout + loco profile + anim profile 2. **New equipment piece** = sections/sockets (+ optional collider) + studio views 3. **New contact rule** = impact profile + rules callback, no hit-system fork 4. **New ball sport** = PlayObject + possession params + arena goals + AI facts 5. **New locomotion** = one module implementing `ILocomotion` + foot policy 6. **New sport AI** = roles writing intents/actions into the same seam as the pad 7. **Regression** = headless metrics + shot sheets vs reference photos for that pack 8. **Hockey still runs** as a pack on top of the same cores Not required for “framework done”: full NHL parity, licensing, netcode, franchise modes (those are product; see ROADMAP). --- ## 9. Risks & non-goals | Risk | Mitigation | |------|------------| | Over-abstract before second sport | Extract only when hockey + one other pack demand the seam | | Run gait looks like skating forever | Foot plant policy is a hard gate for sport #2 | | Proxy pile-ups | Dedicated multi-body scenarios before rugby/football | | Mocap FOMO | Keep procedural + layer API; add clips when content exists | | img2mesh becomes “AI will make the gear” | Refs guide humans/tools; runtime assets stay authored procedural/glTF | | Determinism ignored | Prove early; harness replays depend on it | | God-object `match.js` | Event log + rules plugin from the start of Phase 5 | **Non-goals:** replacing Unity/Unreal; full photogrammetry pipeline; every Olympic sport in year one; network-complete framework before single-player packs feel good. --- ## 10. Suggested near-term decisions 1. **Keep hockey playable on main** while extracting — no big-bang rewrite. 2. **Name the framework** (e.g. still `tilt` core + `sports/hockey`, or promote Ludus-lineage body stack to a shared package both Ludus and tilt consume). 3. **Second pack choice** determines Phase 2–4 emphasis: - Fighting → impact, reaction layers, stamina - Soccer → run plant, ball object, large arena 4. **Studio first among tools** — equipment and poses improve only as fast as the ref-sheet loop; that loop is already the right shape. 5. **Do not wait for mocap** to generalize animation runtime; wait for mocap to *fill* it. --- ## 11. One-page checklist — “left to expand” **Core extractions** - [ ] Locomotion interface + run/plant model - [ ] Foot / arm / look IK module - [ ] Anim layer stack + clip adapter - [ ] Athlete factory + data loadouts - [ ] EquipmentDef / ToolDef schema - [ ] Impact profiles + rules hooks - [ ] PlayObject + generic possession - [ ] ArenaDef + surfaces - [ ] Brain blackboard + roles - [ ] Match phase machine + events - [ ] Action-map input **Harness / content pipeline** - [ ] Sport-registered studio catalogs - [ ] Reference photo overlay + capture matrix - [ ] Metric probes + golden pose/contact tests - [ ] Drill factory for training scenarios **Proof** - [ ] Hockey re-homed as pack - [ ] Second sport pack without core forks - [ ] Determinism + replay of harness scenarios **Explicitly still sport content (never “framework only”)** - Poses, gear shapes, AI tactics, rules edge cases, audio, broadcast, modes, licensing --- ## 12. Bottom line You are closer than a greenfield sports engine because the **hard abstractions are already proven in anger**: - intent-driven locomotion - animator subordinate to physics - limb-level contact from posed ragdolls - limp ↔ driven handoff without teleports - tool-in-hand dependency order - possession as a dial - pure sim + headless tests + reference shot sheets What remains is not “invent sports tech.” It is **peeling hockey off the type system**, turning each proven spike into a **contract + pack content**, and making the **studio/harness** the way every new sport earns visual and mechanical correctness from reference photos and scenario metrics. Hockey ROADMAP remains the depth plan for pack #1. This document is the breadth plan for the chassis underneath packs #1…N.