Orientation fix

public/js/exhibit.js

@@ -69,24 +69,19 @@ function centredCorners(m, w, h) {
 }
 
 // Build the marker->camera matrix (POS-IT), converting js-aruco axes to three.js.
-// js-aruco POS-IT gives the marker pose in a camera frame with X right, Y up,
-// Z toward viewer. Three.js's camera looks down -Z with Y up, so we convert by
-// premultiplying F = diag(1,-1,-1) (flip Y and Z). This is the SAME conversion
-// the working ar-head.js uses, and it is correct for pitch AND roll: tilting the
-// phone up moves an anchored ghost down-screen, and rolling the phone rotates the
-// ghost the same way. (An earlier F*M*F "fix" inverted both — don't reintroduce it.)
-const flipYZ = new THREE.Matrix4().makeScale(1, -1, -1);
-
-// Convert one POS-IT (R,t) solution into a three.js marker->camera matrix.
+// DERIVED FROM REAL DEVICE DATA (orient-debug log): the POS-IT rotation is already
+// correct as-is. The old F=diag(1,-1,-1) premultiply was rotating the whole frame
+// 180 deg about X -> pitch negated + 180 deg roll ("upside down + inverted tilt").
+// The ONLY conversion needed is on the TRANSLATION: three.js's camera looks down
+// -Z (and screen Y is up), so we negate translation Y and Z. Rotation stays
+// untouched, which keeps pitch/roll/yaw matching the real marker exactly.
 function poseToMatrix(R, t) {
-  const M = new THREE.Matrix4().set(
-    R[0][0], R[0][1], R[0][2], t[0],
-    R[1][0], R[1][1], R[1][2], t[1],
-    R[2][0], R[2][1], R[2][2], t[2],
+  return new THREE.Matrix4().set(
+    R[0][0], R[0][1], R[0][2],  t[0],
+    R[1][0], R[1][1], R[1][2], -t[1],   // flip translation Y (screen up)
+    R[2][0], R[2][1], R[2][2], -t[2],   // flip translation Z (in front of -Z cam)
     0, 0, 0, 1
   );
-  M.premultiply(flipYZ);  // F * M  (flip Y & Z: POS-IT frame -> three.js frame)
-  return M;
 }
 
 // POS-IT returns TWO solutions for a planar marker (the real pose and a mirror