IMU system: react to gravity changes (#3254)

Signed-off-by: Shivang <shivangso23@iitk.ac.in>
Signed-off-by: Shivang <75626127+IceShuttle@users.noreply.github.com>
Co-authored-by: Alejandro Hernández Cordero <ahcorde@gmail.com>

Author: IceShuttle

src/systems/imu/Imu.cc

@@ -319,6 +319,17 @@ void ImuPrivate::Update(const EntityComponentManager &_ecm)
           const auto &imuWorldPose = _worldPose->Data();
           it->second->SetWorldPose(imuWorldPose);
 
+          // Update World Gravity
+          auto gravity = _ecm.Component<components::Gravity>(worldEntity);
+          if (nullptr != gravity)
+          {
+            it->second->SetGravity(gravity->Data());
+          }
+          else
+          {
+            gzerr << "World missing gravity."  <<
+              "Gravity used by imu sensor may be outdated" << std::endl;
+          }
           // Set the IMU angular velocity (defined in imu's local frame)
           it->second->SetAngularVelocity(_angularVel->Data());