Adaptive temporal smoothing + wider reset gate to reduce jitter without adding lag

public/js/ar/fuse.js

@@ -23,11 +23,20 @@ export class WorldFuser {
     this.anchorMats = new Map(); // markerId -> Matrix4
     this.smoothPos = null;
     this.smoothQuat = null;
-    this.posAlpha = 0.35;  // smoothing factors (higher = snappier)
-    this.quatAlpha = 0.35;
+    // adaptive smoothing bounds: minAlpha when nearly still (heavy smoothing,
+    // kills jitter), maxAlpha when moving fast (light smoothing, stays responsive)
+    this.minAlpha = 0.08;
+    this.maxAlpha = 0.6;
     this.lastFuseT = 0;
   }
 
+  // Map a motion magnitude between [lo, hi] thresholds to an alpha in
+  // [minAlpha, maxAlpha]. Below lo => minAlpha (still); above hi => maxAlpha (moving).
+  adaptAlpha(delta, lo, hi) {
+    const tt = Math.min(1, Math.max(0, (delta - lo) / (hi - lo)));
+    return this.minAlpha + (this.maxAlpha - this.minAlpha) * tt;
+  }
+
   setScene(scene) {
     this.anchorMats.clear();
     for (const a of scene.anchors || []) {
@@ -72,12 +81,20 @@ export class WorldFuser {
     }
     pos.multiplyScalar(1 / wSum);
 
-    // temporal smoothing
+    // temporal smoothing — adaptive: smooth hard when nearly still (kills jitter),
+    // loosen when genuinely moving (stays responsive). Reset only after a real
+    // tracking gap so brief single-frame dropouts don't cause a visible snap.
     const now = performance.now();
-    if (this.smoothPos && now - this.lastFuseT < 500) {
-      this.smoothPos.lerp(pos, this.posAlpha);
+    if (this.smoothPos && now - this.lastFuseT < 1500) {
+      // positional delta in cm; rotational delta in radians
+      const dPos = this.smoothPos.distanceTo(pos);
       if (this.smoothQuat.dot(quat) < 0) quat.set(-quat.x, -quat.y, -quat.z, -quat.w);
-      this.smoothQuat.slerp(quat, this.quatAlpha);
+      const dAng = 2 * Math.acos(Math.min(1, Math.abs(this.smoothQuat.dot(quat))));
+      // map motion -> alpha in [minAlpha, maxAlpha]. Small motion => small alpha.
+      const pAlpha = this.adaptAlpha(dPos, 0.5, 6);    // still<0.5cm .. moving>6cm
+      const qAlpha = this.adaptAlpha(dAng, 0.01, 0.15); // still<0.6° .. moving>8.6°
+      this.smoothPos.lerp(pos, pAlpha);
+      this.smoothQuat.slerp(quat, qAlpha);
     } else {
       this.smoothPos = pos.clone();
       this.smoothQuat = quat.clone();