Reworked geometric algebra. Accesses Basis via get_column.

plugin/src/main/cpp/extensions/openxr_fb_body_tracking_extension_wrapper.cpp

@@ -314,17 +314,22 @@ void OpenXRFbBodyTrackingExtensionWrapper::_on_process() {
 	//   with how models are designed, rather than the Meta positions of
 	//   the tips of the clavicles.
 	if (locations.isActive) {
+		// Construct a root under the hips pointing forwards
+		// IE, +z aligns with hips & user's real-world forward.
+		// (Remaining, however, on the XRorigin / Global XZ plane; root's basis rotated around Y to fit)
+
 		// Get the hips transform
 		Transform3D hips = xr_body_tracker->get_joint_transform(XRBodyTracker::JOINT_HIPS);
-
-		// Construct the root under the hips pointing forwards
 		Vector3 root_y = Vector3(0.0, 1.0, 0.0);
-		Vector3 root_z = -hips.basis[Vector3::AXIS_X].cross(root_y);
-		Vector3 root_x = root_y.cross(root_z);
+		Vector3 hips_left = hips.basis.get_column(Vector3::AXIS_X);
+		// flatten hips' left (x basis) on to real-world / global ground plane. Normalize.
+		Vector3 root_x = (hips_left.slide(Vector3(0.0, 1.0, 0.0))).normalized();
+		Vector3 root_z = root_x.cross(root_y);
+		// flatten hips' origin on to ground plane.
 		Vector3 root_o = hips.origin.slide(Vector3(0.0, 1.0, 0.0));
+		// set the actual root transform
 		Transform3D root = Transform3D(root_x, root_y, root_z, root_o).orthonormalized();
 		xr_body_tracker->set_joint_transform(XRBodyTracker::JOINT_ROOT, root);
-		xr_body_tracker->set_pose("default", root, Vector3(), Vector3(), XRPose::XR_TRACKING_CONFIDENCE_HIGH);
 
 		// Distance in meters to push the shoulder joints back from the
 		// clavicle-position to be in-line with the upper arm joints as
@@ -333,7 +338,7 @@ void OpenXRFbBodyTrackingExtensionWrapper::_on_process() {
 
 		// Deduce the shoulder offset from the upper chest transform
 		Transform3D upper_chest = xr_body_tracker->get_joint_transform(XRBodyTracker::JOINT_UPPER_CHEST);
-		Vector3 shoulder_offset = upper_chest.basis[2] * shoulder_z_offset;
+		Vector3 shoulder_offset = upper_chest.basis.get_column(Vector3::AXIS_Z) * shoulder_z_offset;
 
 		// Correct the left shoulder
 		Transform3D left_shoulder = xr_body_tracker->get_joint_transform(XRBodyTracker::JOINT_LEFT_SHOULDER);
@@ -344,6 +349,10 @@ void OpenXRFbBodyTrackingExtensionWrapper::_on_process() {
 		Transform3D right_shoulder = xr_body_tracker->get_joint_transform(XRBodyTracker::JOINT_RIGHT_SHOULDER);
 		right_shoulder.origin += shoulder_offset;
 		xr_body_tracker->set_joint_transform(XRBodyTracker::JOINT_RIGHT_SHOULDER, right_shoulder);
+
+		// Set tracker pose, velocities, confidence.
+		// Good to go.
+		xr_body_tracker->set_pose("default", root, Vector3(), Vector3(), XRPose::XR_TRACKING_CONFIDENCE_HIGH);
 	}
 
 	// Register the XRBodyTracker if necessary