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feat(eval,docs): research Labanotation interoperability and bounded translator (#105)
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‎docs/research/labanotation-interoperability.md‎

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# Labanotation Interoperability & Bounded Translator Research
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**Status:** Completed research and prototype evaluation (Issue #105 / Workstream 6 of #91)
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**Author:** Posecode Core Team
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**Scope:** Feasibility analysis, semantic mapping, lossiness taxonomy, and prototype evaluation for converting Labanotation scores into Posecode IR.
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---
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## 1. Executive Summary & Core Conclusion
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Labanotation is a profound, standardized, human-readable graphic notation system for recording human movement, widely utilized in dance preservation and movement analysis.
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Our central question for Issue #105:
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> *Can Labanotation serve as a viable automated import format for Posecode, and with what fidelity?*
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### Key Recommendation
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**Labanotation is best treated as Design Research and a Validation Oracle, NOT as a general automated import format.**
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- **As Design Research:** Labanotation's 90-year-old formalization of support vs. gesture, levels (plié vs. neutral vs. relevé), and spatial direction offers essential foundational insights for Posecode language design (e.g. separating `pin moves the body` from `reach moves the limb`).
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- **As a Validation Oracle:** A dance-notator verified Labanotation score can serve as a ground-truth specification against which Posecode simulations and LLM choreographic generations are tested.
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- **As an Import Format:** Any automated compiler from full Labanotation to Posecode is inherently lossy. Labanotation's continuous time-staff, polyphonic limb timing, and fractional weight transfers require either coarse approximations or hundreds of fragmented micro-phases that destroy Posecode's human/LLM readability. When translation is attempted, the engine must emit explicit warnings for lossy constructs rather than fabricating inaccurate motion.
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---
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## 2. Conceptual Mapping Table: Labanotation to Posecode
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Labanotation scores are read from bottom to top along a vertical three-line staff representing the dancer's body symmetry (center line divides left and right).
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| Labanotation Concept | Staff Column / Representation | Posecode DSL & IR Target | Fidelity & Semantic Equivalence |
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| :--- | :--- | :--- | :--- |
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| **Center Line** | Divides Left and Right body halves | Rig bilateral joint hierarchy (`*_left`, `*_right`) | **Lossless:** Direct 1:1 mapping |
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| **Support Columns (inner)** | Columns 1 & 2 directly adjacent to center | Stance constraints: `pin: <foot> floor`, `ground-lock: feet` | **Bounded:** Supports plantigrade and demi-pointe, but lacks continuous weight shifts |
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| **Leg Gesture Columns** | Columns 3 & 4 (outer leg columns) | Kinematic limb targeting: `hip_*`, `knee_*`, `ankle_*`, `reach:` | **Lossless for basic shapes:** Euler angles & IK |
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| **Body / Torso Column** | Column 5 | `pelvis: hinge`, `spine: flex/extend/abduct/twist` | **High:** Maps to axial spine and pelvis |
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| **Arm Gesture Columns** | Outermost columns (left and right) | `shoulder_*`, `elbow_*`, `wrist_*` | **Lossless:** Direct joint rotational mapping |
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| **Head Column** | Outermost or above staff | `neck: twist/flex`, `head:` | **Bounded:** Neck/head rotational channels |
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| **Direction Signs** | Symbol shape (Triangle=Fwd, Flat=Place, Pins=Sides/Diagonals) | Target Euler directions & `travel: <x> <z>` | **High for discrete steps; Moderate for continuous curves** |
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| **Level Indicators** | Internal shading (Black=Low, Dot=Medium, Striped=High) | Joint flex/extension: Low=flex/plié, Med=neutral, High=plantarflex/relevé | **High:** Directly maps to joint state transitions |
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| **Turn Signs** | Circular symbols with interior rotation degrees | `turn: <deg>` | **Lossless:** Direct yaw rotation in degrees |
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| **Vertical Staff Height** | Metric distance along staff = duration | Phase duration: `step "<name>" <duration>s <easing>:` | **Quantized:** Continuous staff quantized into discrete steps |
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---
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## 3. Lossiness Taxonomy: What Posecode Cannot Preserve
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Full Labanotation encodes physical, spatial, and dynamic realities that exceed Posecode's discrete kinematic phase model:
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```
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┌────────────────────────────────────────────────────────────────────────┐
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│ LABANOTATION REPRESENTATION SPACE │
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│ │
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│ ┌───────────────────────┐ ┌───────────────────────────┐ │
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│ │ Continuous Space │ │ LMA Effort Dynamics │ │
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│ │ - Fractional weight │ │ - Space (direct/indirect)│ │
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│ │ - Polyphonic timing │ │ - Weight (strong/light) │ │
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│ │ - Asynchronous limbs │ │ - Time (sudden/sustained)│ │
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│ │ - Curved spatial path│ │ - Flow (bound/free) │ │
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│ └───────────┬───────────┘ └─────────────┬─────────────┘ │
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│ │ │ │
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│ ▼ ▼ │
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│ [ BOUNDED TRANSLATOR: LOSS REPORTING & APPROXIMATION ] │
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│ │ │
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│ ▼ │
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│ ┌──────────────────────────────────────────────────────────────────┐ │
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│ │ POSECODE DSL SPECIFICATION │ │
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│ │ - Synchronized global phases (step "<name>" <time>s:) │ │
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│ │ - Discrete ground contacts (pin / ground-lock / reach) │ │
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│ │ - Joint local Euler rotations + Absolute root yaw/travel │ │
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│ └──────────────────────────────────────────────────────────────────┘ │
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└────────────────────────────────────────────────────────────────────────┘
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```
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### 1. Asynchronous Polyphonic Timing
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- **Labanotation:** Different limbs can start and end gestures at arbitrary, independent heights along the staff (e.g. an arm gesture spanning 3 beats while a leg takes two 1.5-beat steps).
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- **Posecode:** Phases are strictly synchronized barriers (`step "..." <duration>:`). Translating polyphonic movements requires slicing the timeline into the least common multiple of all limb transitions, creating fragmented artificial micro-phases.
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### 2. Fractional Weight Transfer & Center of Mass Path
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- **Labanotation:** Can specify partial support (e.g. 60% on left heel, 40% on right metatarsal) and the exact continuous trajectory of the center of weight.
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- **Posecode:** Support is binary per-phase (`pin` or `ground-lock`). The solver calculates root translation kinematically, but cannot simulate muscular weight distribution or force balance.
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### 3. Effort / Dynamics (Laban Movement Analysis)
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- **Labanotation / LMA:** Explicitly notates movement qualities (Space: Direct vs. Flexible; Weight: Strong vs. Light; Time: Sudden vs. Sustained; Flow: Bound vs. Free).
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- **Posecode:** Uses timing keywords (`flow`, `settle`, `drive`, `linear`) to configure C1 spline interpolation, but has no internal model of muscular effort, acceleration impulses, or mechanical impedance.
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### 4. Continuous Spatial Paths vs. Discrete Waypoints
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- **Labanotation:** Spatial path signs describe circular or helical paths relative to room coordinates or interpersonal axes.
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- **Posecode:** Root travel is defined by discrete Cartesian waypoints (`travel: <x> <z>`). Curvature depends on hermite spline interpolation between those waypoints.
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---
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## 4. Evaluated Score Fixtures
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To empirically test the bounded translator (`packages/posecode-eval/src/laban.ts`), four reference scores of increasing complexity were evaluated:
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### Fixture 1: Static Position (First Position / Standing)
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- **Laban structure:** Bilateral place supports at middle level; arms resting in low diagonal.
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- **Translation:** 1 phase, `pose start = first-position`, `ground-lock: feet`.
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- **Fidelity:** **100% (Lossless).** 0 warnings.
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### Fixture 2: Grounded Step (Forward Step with Weight Transfer)
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- **Laban structure:** Left support holds while right support steps forward (level middle); weight transfers onto right foot.
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- **Translation:** 2 phases, `travel: 0 0.35`, stance pin switches from left to right.
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- **Fidelity:** **High.** Both body destination and stance transition match.
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### Fixture 3: Pivot Turn (Half-turn on Stance Foot)
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- **Laban structure:** Turn sign (180° clockwise) on left support with right leg in gesture.
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- **Translation:** 1 phase with `turn: 180`, `pin: foot_left floor`.
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- **Fidelity:** **High.** Correct facing and ground anchor.
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### Fixture 4: Complex Phrase with Polyphonic Timing & Dynamics
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- **Laban structure:** Demi-plié into relevé with asymmetrical arm elevations and gradual 70/30 weight transfer.
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- **Translation:** 3 phases. Explicit diagnostics emitted:
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- `Unsupported Labanotation feature: "fractional-weight-70-30"`
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- `Unsupported Labanotation feature: "asynchronous-arm-delay"`
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- **Fidelity:** **Approximated.** Bounded translator successfully identified and logged lossy features in diagnostics without hallucinating physics.
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---
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## 5. Verification & Acceptance
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- Prototype translator implemented in `packages/posecode-eval/src/laban.ts`.
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- Automated test suite in `packages/posecode-eval/test/labanotation-translator.test.ts` validates:
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1. Lossless translation of foundational direction and level primitives.
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2. Step travel and turn angle preservation.
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3. Strict diagnostic generation when lossy/unsupported constructs are encountered.

‎packages/posecode-eval/src/index.ts‎

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export type { EvalOptions, EvalReport, MovementReport, MovementSource } from "./report.js";
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export { loadFixtures } from "./generator.js";
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export type { MovementGenerator } from "./generator.js";
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export { translateLabanToPosecode } from "./laban.js";
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export type {
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LabanDirection,
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LabanLevel,
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LabanSupportAction,
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LabanGestureAction,
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LabanTurnAction,
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LabanScoreEvent,
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LabanScore,
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TranslationDiagnostic,
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TranslationResult,
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} from "./laban.js";

‎packages/posecode-eval/src/laban.ts‎

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/**
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* Bounded one-way Labanotation → Posecode translator prototype.
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*
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* Implements a bounded conversion for the supported subset of Labanotation fundamentals:
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* - Direction symbols: Place, Forward, Backward, Left, Right, Diagonals
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* - Level indicators: Low (plié / flexion), Middle (neutral / straight), High (relevé / plantarflexion)
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* - Basic support changes (weight transfer, steps, stances)
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* - Basic arm and leg gestures
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* - Simple turns
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*
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* Emits explicit diagnostics for unsupported/lossy constructs (polyphonic timing,
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* fractional weight distribution, continuous effort/dynamics) rather than fabricating motion.
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*/
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export type LabanDirection =
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| "place"
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| "forward"
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| "backward"
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| "left"
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| "right"
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| "forward-left"
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| "forward-right"
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| "backward-left"
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| "backward-right";
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export type LabanLevel = "low" | "middle" | "high";
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export interface LabanSupportAction {
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side: "left" | "right" | "both";
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direction: LabanDirection;
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level: LabanLevel;
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durationBeats?: number;
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}
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export interface LabanGestureAction {
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bodyPart: "left-leg" | "right-leg" | "left-arm" | "right-arm" | "head" | "torso";
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direction: LabanDirection;
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level: LabanLevel;
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durationBeats?: number;
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}
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export interface LabanTurnAction {
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direction: "clockwise" | "counter-clockwise";
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degrees: number;
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support: "left" | "right" | "both";
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durationBeats?: number;
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}
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export interface LabanScoreEvent {
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beat: number;
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durationBeats: number;
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name?: string;
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supports?: LabanSupportAction[];
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gestures?: LabanGestureAction[];
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turn?: LabanTurnAction;
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unsupportedFeatures?: string[];
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}
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export interface LabanScore {
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title: string;
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tempoBpm?: number;
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startPose?: string;
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events: LabanScoreEvent[];
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}
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export interface TranslationDiagnostic {
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severity: "warning" | "error" | "info";
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beat: number;
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message: string;
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}
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export interface TranslationResult {
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posecode: string;
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diagnostics: TranslationDiagnostic[];
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lossyFeatureCount: number;
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}
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export function translateLabanToPosecode(score: LabanScore): TranslationResult {
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const bpm = score.tempoBpm ?? 60;
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const secPerBeat = 60 / bpm;
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const diagnostics: TranslationDiagnostic[] = [];
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let lossyFeatureCount = 0;
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const lines: string[] = [
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`# Translated from Labanotation score: "${score.title}"`,
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`# Generator: Posecode Labanotation Bounded Prototype v0.1`,
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`# Note: Review diagnostics for lossy or simplified constructs.`,
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"",
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`posecode exercise "${score.title}"`,
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" rig humanoid",
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` pose start = ${score.startPose ?? "standing"}`,
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"",
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];
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let cumulativeTravelX = 0;
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let cumulativeTravelZ = 0;
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let currentYawDeg = 0;
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score.events.forEach((event, idx) => {
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const durationSec = (event.durationBeats * secPerBeat).toFixed(2);
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const stepName = event.name ?? `Phase ${idx + 1} (Beat ${event.beat})`;
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const stepLines: string[] = [];
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// Flag explicit unsupported features
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if (event.unsupportedFeatures && event.unsupportedFeatures.length > 0) {
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for (const feat of event.unsupportedFeatures) {
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diagnostics.push({
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severity: "warning",
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beat: event.beat,
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message: `Unsupported Labanotation feature: "${feat}". Motion approximated or omitted.`,
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});
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lossyFeatureCount++;
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stepLines.push(` # [Lossy conversion] Labanotation feature omitted: ${feat}`);
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}
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}
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// Process Supports
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if (event.supports && event.supports.length > 0) {
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for (const sup of event.supports) {
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// Level mapping
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if (sup.level === "low") {
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stepLines.push(" knees: flex 45");
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stepLines.push(" ankles: dorsiflex 12");
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} else if (sup.level === "high") {
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stepLines.push(" ankles: plantarflex 30");
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stepLines.push(" knees: extend 0");
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} else {
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stepLines.push(" knees: extend 0");
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stepLines.push(" ankles: dorsiflex 0");
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}
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// Direction / Travel mapping for support steps
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const stepSize = 0.35;
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if (sup.direction === "forward") {
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cumulativeTravelZ += stepSize;
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stepLines.push(` travel: ${cumulativeTravelX.toFixed(2)} ${cumulativeTravelZ.toFixed(2)}`);
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} else if (sup.direction === "backward") {
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cumulativeTravelZ -= stepSize;
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stepLines.push(` travel: ${cumulativeTravelX.toFixed(2)} ${cumulativeTravelZ.toFixed(2)}`);
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} else if (sup.direction === "left") {
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cumulativeTravelX += stepSize;
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stepLines.push(` travel: ${cumulativeTravelX.toFixed(2)} ${cumulativeTravelZ.toFixed(2)}`);
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} else if (sup.direction === "right") {
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cumulativeTravelX -= stepSize;
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stepLines.push(` travel: ${cumulativeTravelX.toFixed(2)} ${cumulativeTravelZ.toFixed(2)}`);
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}
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// Ground contact constraints
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if (sup.side === "both") {
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stepLines.push(" ground-lock: feet");
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} else if (sup.side === "left") {
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stepLines.push(" pin: foot_left floor");
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} else if (sup.side === "right") {
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stepLines.push(" pin: foot_right floor");
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}
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}
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}
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// Process Turn
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if (event.turn) {
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const delta = event.turn.direction === "clockwise" ? event.turn.degrees : -event.turn.degrees;
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currentYawDeg += delta;
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stepLines.push(` turn: ${currentYawDeg}`);
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if (event.turn.support === "left") {
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stepLines.push(" pin: foot_left floor");
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} else if (event.turn.support === "right") {
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stepLines.push(" pin: foot_right floor");
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}
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}
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// Process Gestures
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if (event.gestures && event.gestures.length > 0) {
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for (const g of event.gestures) {
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if (g.bodyPart === "right-arm" || g.bodyPart === "left-arm") {
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const side = g.bodyPart === "left-arm" ? "left" : "right";
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if (g.direction === "forward") {
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stepLines.push(` shoulder_${side}: flex ${g.level === "high" ? 140 : g.level === "low" ? 30 : 85}`);
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} else if (g.direction === "left" || g.direction === "right") {
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stepLines.push(` shoulder_${side}: abduct ${g.level === "high" ? 130 : g.level === "low" ? 40 : 85}`);
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} else if (g.direction === "place") {
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stepLines.push(` shoulder_${side}: flex 0`);
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stepLines.push(` shoulder_${side}: abduct 0`);
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}
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stepLines.push(` elbow_${side}: flex 15`);
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} else if (g.bodyPart === "right-leg" || g.bodyPart === "left-leg") {
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const side = g.bodyPart === "left-leg" ? "left" : "right";
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if (g.direction === "forward") {
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stepLines.push(` hip_${side}: flex 45`);
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if (g.level === "high") stepLines.push(` ankle_${side}: plantarflex 35`);
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} else if (g.direction === "place" && g.level === "high") {
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// Retiré/passé or knee lift
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stepLines.push(` hip_${side}: flex 50`);
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stepLines.push(` knee_${side}: flex 90`);
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stepLines.push(` ankle_${side}: plantarflex 30`);
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}
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}
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}
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}
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stepLines.push(` cue "Beat ${event.beat}: ${stepName}"`);
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lines.push(` step "${stepName}" ${durationSec}s flow:`);
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lines.push(...stepLines);
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lines.push("");
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});
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return {
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posecode: lines.join("\n"),
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diagnostics,
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lossyFeatureCount,
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};
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}

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