Add dev ghost-freeze (static spawn position) to isolate tracking jitter from float animation; toggle via tracking HUD tap

public/js/exhibit.js

@@ -28,6 +28,12 @@ const CAM_CORR = {
 const CAM_MODES = ['none', 'y180', 'x180', 'z180'];
 let camMode = 'none';   // default: none — rely on pose.js conjugation alone
 
+/* Diagnostic: freeze all ghost motion (bob/sway/wander/path) so ghosts sit at their
+ * static spawn position. Lets you tell tracking jitter apart from the built-in float
+ * animation — if a frozen ghost still moves, that's the camera pose, not the ghost.
+ * Defaults ON in dev; tap the bottom third of the HUD tracking line to toggle. */
+let freezeGhosts = false;
+
 let info = { mode: 'dev' };
 let scene3, camera3, renderer, video, canvas2d, ctx2d;
 let detector, poseEst, fuser;
@@ -55,7 +61,7 @@ function updateDbg(fusedQuat, markerCount, spread) {
   const v3 = v => `(${v.x.toFixed(2)},${v.y.toFixed(2)},${v.z.toFixed(2)})`;
   const spreadLine = markerCount > 1 ? `  spread ${spread.toFixed(1)}cm` : '';
   dbgEl.textContent =
-    `rot ${getRotMode()}  cam ${camMode}   (tap to cycle)\n` +
+    `rot ${getRotMode()}  cam ${camMode}  ${freezeGhosts ? 'FROZEN' : 'moving'}\n` +
     `markers ${markerCount}${spreadLine}\n${rawLine}\nview ${v3(view)}\nup   ${v3(up)}\n` +
     `pos  ${v3(camera3.position)}`;
 }
@@ -139,6 +145,7 @@ async function start() {
 
   // dev-mode pose readout + tap-to-cycle correction modes
   if (info.mode === 'dev') {
+    freezeGhosts = true;   // start static so tracking jitter is isolated from ghost float
     dbgEl = $('#dbg');
     if (dbgEl) {
       dbgEl.style.display = 'block';
@@ -155,6 +162,12 @@ async function start() {
         }
       });
     }
+    // tap the tracking HUD chip to toggle ghost motion freeze
+    const trk = $('#trk');
+    if (trk) {
+      trk.style.pointerEvents = 'auto';
+      trk.addEventListener('click', () => { freezeGhosts = !freezeGhosts; });
+    }
   }
 
   // network
@@ -278,10 +291,16 @@ function loop(t) {
   const now = Date.now() + clockOffset;
   for (const { rec, group } of activeGhosts.values()) {
     ghostTransform(rec, now, _tmp);
-    group.position.copy(_tmp.position);
-    group.rotation.y = _tmp.rotationY;
+    if (freezeGhosts) {
+      // hold at the static spawn position; keep only the fade opacity from _tmp
+      group.position.set(rec.pos[0], rec.pos[1], rec.pos[2]);
+      group.rotation.y = 0;
+    } else {
+      group.position.copy(_tmp.position);
+      group.rotation.y = _tmp.rotationY;
+    }
     group.userData.setOpacity(_tmp.opacity * 0.92);
-    group.userData.tick(t / 1000);
+    group.userData.tick(freezeGhosts ? 0 : t / 1000);
   }
 
   // HUD