use heading same as velocity heading (if velocity >0)

modules/perception/lidar/lib/tracker/common/tracked_object.cc

@@ -194,7 +194,6 @@ void TrackedObject::ToObject(base::ObjectPtr obj) const {
      what a pity!
   */
   obj->direction = output_direction.cast<float>();
-  obj->theta = std::atan2(obj->direction[1], obj->direction[0]);
   // obj theta_variance not calculate in tracker, keep default
   obj->center = output_center;
   // obj center_uncertainty not calculate in tracker, keep default
@@ -209,6 +208,11 @@ void TrackedObject::ToObject(base::ObjectPtr obj) const {
   obj->velocity_uncertainty = output_velocity_uncertainty.cast<float>();
   obj->velocity_converged = converged;
   obj->tracking_time = tracking_time;
+  if (obj->velocity.norm() > 0) {
+    obj->theta = std::atan2(obj->velocity[1], obj->velocity[0]);
+  } else {
+    obj->theta = std::atan2(obj->direction[1], obj->direction[0]);
+  }
   // obj latest_tracked_time not calculate in tracker, keep default
   // obj car_light not calculate in tracker, keep default
   // obj lidar_supplement cloud_world has passed in *obj = *object_ptr