web/gestures.js

// Landmarks -> performance controls. Every control is normalized [0,1] and
// derived from in-plane geometry normalized by palm size, so it is invariant to
// how close the hand is to the lens. Four INDEPENDENT controls per hand chosen so
// they don't false-trigger each other:
//   HEIGHT  (wrist y)                  -> the hero filter sweep
//   ROLL    (wrist->middle_mcp tilt)   -> turntable warp (tempo/pitch)
//   PINCH   (thumb<->index)            -> reverb / delay space  [ignores m/r/pinky]
//   FIST    (middle+ring+pinky curl)   -> stutter buildup       [ignores thumb/index]
import { H, dist, norm, clamp } from "./math.js";

const palmSize = (lm) => dist(lm[H.WRIST], lm[H.MIDDLE_MCP]) || 1e-6;

export function controls(lm) {
  const ps = palmSize(lm);

  // HEIGHT: 1 - wrist.y, mapped so a comfortable raise spans the full range.
  const height = norm(1 - lm[H.WRIST].y, 0.18, 0.82);

  // PINCH: thumb tip to index tip over palm. ~0.25 pinched … ~1.1 spread.
  // Tight pinch => high "space" send.
  const pinchRaw = dist(lm[H.THUMB_TIP], lm[H.INDEX_TIP]) / ps;
  const pinch = 1 - norm(pinchRaw, 0.28, 0.95);

  // FIST: how curled the middle/ring/pinky are (tip distance to wrist over palm).
  // open hand ~2.0, tight fist ~1.05 -> fist amount near 1.
  const curl = (dist(lm[H.MIDDLE_TIP], lm[H.WRIST]) +
                dist(lm[H.RING_TIP],   lm[H.WRIST]) +
                dist(lm[H.PINKY_TIP],  lm[H.WRIST])) / (3 * ps);
  const fist = 1 - norm(curl, 1.15, 1.95);

  // ROLL: tilt of the wrist->middle_mcp vector. 0=straight up; +right / -left.
  const dx = lm[H.MIDDLE_MCP].x - lm[H.WRIST].x;
  const dy = lm[H.MIDDLE_MCP].y - lm[H.WRIST].y;
  const rollAngle = Math.atan2(dx, -dy);           // radians
  const roll = norm(rollAngle, -0.7, 0.7);         // 0.5 = upright

  return { height, pinch, fist, roll, cx: clamp(lm[H.WRIST].x, 0, 1) };
}