Animation naturalness: spline interpolation, foot-flat, bar grip, secondary motion (L2–L4.2)

.gitignore

@@ -6,3 +6,8 @@ coverage/
 .vite/
 .vercel
 .claude/worktrees/
+
+# Mocap clip binaries: sourced from Mixamo, loaded from storage/CDN, not committed.
+playground/public/clips/*.fbx
+playground/public/clips/*.glb
+playground/public/clips/.DS_Store

docs/superpowers/plans/2026-07-11-l3-1-foot-flat.md

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+# L3.1 — Foot-Flat Correction Implementation Plan
+
+> **For agentic workers:** Use superpowers:executing-plans to implement task-by-task. Steps use checkbox (`- [ ]`) syntax.
+
+**Goal:** Keep planted soles level with the floor so grounded lower-body moves (squat, lunge, deadlift) rest flat instead of balancing on the toes, without disturbing authored angles, tiptoe moves, or swing feet.
+
+**Architecture:** A new `levelPlantedFeet(m, activeGroundLock)` in `contacts.ts` rotates each ground-locked ankle so its sole normal (local `-Y`) points world-down, weighted by planted-ness and skipped on authored plantarflex. Wired into the viewer `frame()` (before the floor clamp) and `load()`.
+
+**Tech Stack:** TypeScript ESM (`.js` specifiers), Three.js, Vitest.
+
+## Global Constraints
+
+- Immutability: never mutate shared keyframe quaternions; write bone quaternions in place only (matches `alignFloorPalms`).
+- `plantarflex` = ankle local Euler **+X** (toe-down); `dorsiflex` = **−X**. Sole-down normal = ankle local `(0,−1,0)`.
+- Constants named + exported for tests: `PLANT_FADE = 0.06` (m), `PLANTARFLEX_SKIP = 15 * DEG` (rad).
+- Reuse the `alignFloorPalms` idiom (`getWorldQuaternion` → `setFromUnitVectors(current, DOWN)` → back to local via parent inverse).
+- Clamp the corrected ankle to its ROM (`eulerRomFor("ankle_left"/"ankle_right")`), widened to admit the authored angle.
+- TDD; keep every existing suite green; typecheck clean.
+- Test a file: `npx vitest run <path>` from repo root.
+
+---
+
+### Task 1: `levelPlantedFeet` in contacts.ts
+
+**Files:**
+- Modify: `packages/posecode-render/src/contacts.ts`
+- Test: `packages/posecode-render/test/contacts.test.ts` (create if absent)
+
+**Interfaces:**
+- Produces: `levelPlantedFeet(m: Mannequin, activeGroundLock: readonly string[]): void`, plus exported consts `PLANT_FADE`, `PLANTARFLEX_SKIP`.
+
+- [ ] **Step 1: Write the failing tests**
+
+```ts
+// packages/posecode-render/test/contacts.test.ts
+import { describe, it, expect } from "vitest";
+import * as THREE from "three";
+import { buildMannequin } from "../src/mannequin.js";
+import { levelPlantedFeet } from "../src/contacts.js";
+
+const DEG = Math.PI / 180;
+
+/** World-space sole normal (ankle local -Y) for a foot. */
+function soleNormal(m: ReturnType<typeof buildMannequin>, side: "left" | "right") {
+  const ankle = m.bones.get(`ankle_${side}`)!;
+  const q = ankle.getWorldQuaternion(new THREE.Quaternion());
+  return new THREE.Vector3(0, -1, 0).applyQuaternion(q).normalize();
+}
+
+describe("levelPlantedFeet", () => {
+  it("levels a tilted planted foot so the sole faces down", () => {
+    const m = buildMannequin();
+    // Tilt the whole leg forward by rotating the knee so the foot pitches.
+    m.bones.get("knee_left")!.rotation.x = 40 * DEG;
+    m.root.updateMatrixWorld(true);
+    levelPlantedFeet(m, ["feet"]);
+    m.root.updateMatrixWorld(true);
+    const n = soleNormal(m, "left");
+    // sole normal points world-down (0,-1,0): dot with DOWN ~ 1
+    expect(n.dot(new THREE.Vector3(0, -1, 0))).toBeGreaterThan(0.98);
+  });
+
+  it("leaves an authored-plantarflex foot on its toes", () => {
+    const m = buildMannequin();
+    m.bones.get("ankle_left")!.rotation.x = 30 * DEG; // plantarflex (toe-down)
+    m.root.updateMatrixWorld(true);
+    const before = m.bones.get("ankle_left")!.quaternion.clone();
+    levelPlantedFeet(m, ["feet"]);
+    expect(m.bones.get("ankle_left")!.quaternion.angleTo(before)).toBeLessThan(1e-6);
+  });
+
+  it("does not touch a swing foot lifted off the floor", () => {
+    const m = buildMannequin();
+    // Lift the foot well above the floor by bending the knee back and raising hip.
+    m.bones.get("hip_left")!.rotation.x = -60 * DEG;
+    m.root.position.y = 0.5;
+    m.root.updateMatrixWorld(true);
+    const before = m.bones.get("ankle_left")!.quaternion.clone();
+    levelPlantedFeet(m, ["feet"]);
+    expect(m.bones.get("ankle_left")!.quaternion.angleTo(before)).toBeLessThan(1e-3);
+  });
+});
+```
+
+- [ ] **Step 2: Run to verify failure**
+
+Run: `npx vitest run packages/posecode-render/test/contacts.test.ts`
+Expected: FAIL — `levelPlantedFeet` not exported.
+
+- [ ] **Step 3: Implement `levelPlantedFeet`** (append to `contacts.ts`)
+
+```ts
+import { eulerRomFor } from "posecode-parser";
+
+const SOLE_LOCAL = new THREE.Vector3(0, -1, 0);
+const DEG = Math.PI / 180;
+/** Foot mesh-bottom height at/below which the sole is fully leveled (m). */
+export const PLANT_FADE = 0.06;
+/** Authored plantarflex (ankle local +X) beyond this opts out of leveling (rad). */
+export const PLANTARFLEX_SKIP = 15 * DEG;
+
+const FOOT_SIDES: Array<"left" | "right"> = ["left", "right"];
+const TMP_EULER = new THREE.Euler();
+
+/**
+ * Level each ground-locked foot: rotate the ankle so the sole normal points
+ * world-down (the whole sole rests flat), weighted by how planted the foot is
+ * and skipped when the ankle is authored into plantarflexion (tiptoe intent).
+ * Analogue of `alignFloorPalms` for feet.
+ */
+export function levelPlantedFeet(m: Mannequin, activeGroundLock: readonly string[]): void {
+  if (!activeGroundLock.includes("feet")) return;
+  let changed = false;
+  for (const side of FOOT_SIDES) {
+    const ankle = m.bones.get(`ankle_${side}`);
+    if (!ankle?.parent) continue;
+    // Tiptoe opt-out: authored plantarflex (local +X) beyond the threshold.
+    TMP_EULER.setFromQuaternion(ankle.quaternion, "XYZ");
+    if (TMP_EULER.x > PLANTARFLEX_SKIP) continue;
+    // Planted-ness weight from the foot mesh bottom height.
+    const box = new THREE.Box3().setFromObject(ankle);
+    const y = Number.isFinite(box.min.y) ? box.min.y : 0;
+    const weight = THREE.MathUtils.clamp((PLANT_FADE - y) / PLANT_FADE, 0, 1);
+    if (weight <= 1e-3) continue;
+    // Minimal rotation aligning the sole normal to world-down.
+    const world = ankle.getWorldQuaternion(new THREE.Quaternion());
+    const current = SOLE_LOCAL.clone().applyQuaternion(world).normalize();
+    const correction = new THREE.Quaternion().setFromUnitVectors(current, DOWN);
+    if (weight < 1) correction.slerp(new THREE.Quaternion(), 1 - weight);
+    const desiredWorld = correction.multiply(world);
+    const parentWorld = ankle.parent.getWorldQuaternion(new THREE.Quaternion());
+    const local = parentWorld.invert().multiply(desiredWorld);
+    // Clamp to ankle ROM, widened to admit the authored angle.
+    const rom = eulerRomFor(`ankle_${side}`);
+    if (rom) {
+      TMP_EULER.setFromQuaternion(local, "XYZ");
+      const authored = new THREE.Euler().setFromQuaternion(ankle.quaternion, "XYZ");
+      const cx = THREE.MathUtils.clamp(
+        TMP_EULER.x,
+        Math.min(rom.x.min * DEG, authored.x),
+        Math.max(rom.x.max * DEG, authored.x),
+      );
+      const cz = THREE.MathUtils.clamp(
+        TMP_EULER.z,
+        Math.min(rom.z.min * DEG, authored.z),
+        Math.max(rom.z.max * DEG, authored.z),
+      );
+      TMP_EULER.set(cx, TMP_EULER.y, cz, "XYZ");
+      local.setFromEuler(TMP_EULER);
+    }
+    ankle.quaternion.copy(local);
+    changed = true;
+  }
+  if (changed) m.root.updateMatrixWorld(true);
+}
+```
+
+(Note: `DOWN` already exists at the top of `contacts.ts`.)
+
+- [ ] **Step 4: Run to verify pass**
+
+Run: `npx vitest run packages/posecode-render/test/contacts.test.ts`
+Expected: PASS (3 tests).
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add packages/posecode-render/src/contacts.ts packages/posecode-render/test/contacts.test.ts
+git commit -m "feat(render): levelPlantedFeet — plantigrade foot-flat correction"
+```
+
+---
+
+### Task 2: Wire into the viewer frame loop + load
+
+**Files:**
+- Modify: `packages/posecode-render/src/index.ts`
+- Test: `packages/posecode-render/test/render.test.ts` (add end-to-end squat-flat test)
+
+**Interfaces:**
+- Consumes: `levelPlantedFeet` (Task 1).
+
+- [ ] **Step 1: Write the failing end-to-end test** (append to `render.test.ts`)
+
+```ts
+it("rests a squatting foot flat on the floor (not on the toes)", () => {
+  const src = [
+    'posecode exercise "sq"',
+    "  rig humanoid",
+    "  pose start = standing",
+    '  step "Descend" 1s settle:',
+    "    hips: flex 80",
+    "    knees: flex 95",
+    "    pelvis: hinge 25",
+    "    ground-lock: feet",
+  ].join("\n");
+  const { ir } = parse(src);
+  const tl = buildTimeline(ir!);
+  const m = buildMannequin();
+  tl.sample(1, m.bones);
+  m.root.updateMatrixWorld(true);
+  // Simulate the frame-loop contact stages relevant to feet:
+  groundFigure(m);
+  applyGroundLock(m, ["feet"]);
+  levelPlantedFeet(m, ["feet"]);
+  m.root.updateMatrixWorld(true);
+  const ankle = m.bones.get("ankle_left")!;
+  const soleNormal = new THREE.Vector3(0, -1, 0)
+    .applyQuaternion(ankle.getWorldQuaternion(new THREE.Quaternion()))
+    .normalize();
+  expect(soleNormal.dot(new THREE.Vector3(0, -1, 0))).toBeGreaterThan(0.9); // sole ~flat
+});
+```
+
+Add `levelPlantedFeet` to the render.test.ts import from `../src/contacts.js`.
+
+- [ ] **Step 2: Run to verify failure**
+
+Run: `npx vitest run packages/posecode-render/test/render.test.ts`
+Expected: FAIL — `levelPlantedFeet` not imported / sole not level.
+
+- [ ] **Step 3: Wire into `index.ts`**
+
+Import alongside the existing contacts import:
+
+```ts
+import { alignFloorPalms, levelPlantedFeet } from "./contacts.js";
+```
+
+In `frame()`, immediately after the `alignFloorPalms(mannequin, info.reaches, info.pins);` line and before the floor-clamp bbox block:
+
+```ts
+      levelPlantedFeet(mannequin, info.groundLock);
+```
+
+In `load()`, after `groundFigureOf(mannequin);` and before `captureGroundTargets();`:
+
+```ts
+      levelPlantedFeet(mannequin, timeline.sample(0, mannequin.bones).groundLock);
+```
+
+(If calling `sample` twice is awkward, capture the phase-0 groundLock from `timeline.segments`/IR instead; simplest is to read `ir.phases[0]?.groundLock ?? []`.)
+
+- [ ] **Step 4: Run to verify pass**
+
+Run: `npx vitest run packages/posecode-render`
+Expected: PASS, all render tests green.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add packages/posecode-render/src/index.ts packages/posecode-render/test/render.test.ts
+git commit -m "feat(render): apply foot-flat in the viewer frame loop and on load"
+```
+
+---
+
+### Task 3: Editor discoverability + squat demo fix + full verify
+
+**Files:**
+- Modify: `packages/posecode-language/src/vocab.ts` (`ground-lock` doc)
+- Modify: `spec/examples/squat.posecode` (drop the spurious plantarflex)
+
+- [ ] **Step 1: Update the ground-lock doc**
+
+```ts
+// vocab.ts KEYWORD_DOCS
+  "ground-lock": "Pins effectors (hands / feet) to the floor for this phase. Planted feet auto-level flat to the floor unless the ankle is plantarflexed (tiptoe).",
+```
+
+- [ ] **Step 2: Fix the squat demo**
+
+In `spec/examples/squat.posecode`, remove the `ankles: plantarflex 50` line from the Descend
+step (and its `plantarflex 0` in Drive up), letting foot-flat land the sole. Keep everything
+else.
+
+- [ ] **Step 3: Language tests + full suite + typecheck**
+
+Run: `npx vitest run` (whole workspace) and `npm run typecheck`.
+Expected: all green; the 76 example tests still pass (squat still parses, now flatter).
+
+- [ ] **Step 4: Browser verify**
+
+Start the playground (`preview_start name playground`), open `/play.html#doc=squat` and
+`/play.html#doc=releve`. Confirm: squat rests flat on both feet; relevé stays on the balls of
+the feet. Check console for errors. Screenshot both.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add packages/posecode-language/src/vocab.ts spec/examples/squat.posecode
+git commit -m "feat: squat rests flat via foot-flat; document ground-lock leveling (L3.1)"
+```
+
+---
+
+## Self-Review
+
+- Foot-flat mechanism (align sole to down) → Task 1. ✅
+- Planted-ness soft blend → Task 1 (`weight`). ✅
+- Plantarflex opt-out → Task 1 (`PLANTARFLEX_SKIP`). ✅
+- ROM clamp risk mitigation → Task 1 (eulerRomFor widen). ✅
+- Frame-loop + load wiring → Task 2. ✅
+- DSL discoverability (no new keyword) → Task 3 Step 1. ✅
+- Squat demo + relevé opt-out verification → Task 3. ✅
+- Tests first each task; existing suites green → all tasks. ✅
+- **Placeholder scan:** none. **Type consistency:** `levelPlantedFeet(m, activeGroundLock)`,
+  `PLANT_FADE`, `PLANTARFLEX_SKIP` used consistently.