From 070fed948daba630cb51e753313e511e7ab164fb Mon Sep 17 00:00:00 2001
From: Steve Peters <scpeters@openrobotics.org>
Date: Thu, 20 Jun 2024 16:05:50 -0700
Subject: [PATCH 1/2] Add GravityEnabled boolean component

Signed-off-by: Steve Peters <scpeters@openrobotics.org>
---
 include/gz/sim/components/Gravity.hh | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/gz/sim/components/Gravity.hh b/include/gz/sim/components/Gravity.hh
index fe3cf88a9f..713e797acf 100644
--- a/include/gz/sim/components/Gravity.hh
+++ b/include/gz/sim/components/Gravity.hh
@@ -36,6 +36,11 @@ namespace components
   /// \brief Store the gravity acceleration.
   using Gravity = Component<math::Vector3d, class GravityTag>;
   IGN_GAZEBO_REGISTER_COMPONENT("ign_gazebo_components.Gravity", Gravity)
+
+  /// \brief Store the gravity acceleration.
+  using GravityEnabled = Component<bool, class GravityEnabledTag>;
+  IGN_GAZEBO_REGISTER_COMPONENT(
+      "ign_gazebo_components.GravityEnabled", GravityEnabled)
 }
 }
 }

From 85231c7e0ab28b97face371e8b74a39a32948821 Mon Sep 17 00:00:00 2001
From: youhy <haoyuan2019@outlook.com>
Date: Sun, 23 Jun 2024 12:11:37 -0500
Subject: [PATCH 2/2] change zero gravity vector to component gravityenabled

Signed-off-by: youhy <haoyuan2019@outlook.com>
---
 src/SdfEntityCreator.cc        |  5 ++---
 src/systems/physics/Physics.cc | 21 ++++++---------------
 2 files changed, 8 insertions(+), 18 deletions(-)

diff --git a/src/SdfEntityCreator.cc b/src/SdfEntityCreator.cc
index a84343fd42..71c295db9b 100644
--- a/src/SdfEntityCreator.cc
+++ b/src/SdfEntityCreator.cc
@@ -590,10 +590,9 @@ Entity SdfEntityCreator::CreateEntities(const sdf::Link *_link)
 
   if (!_link->EnableGravity())
   {
-    // If disable gravity, create a gravity component to the entity
-    // This gravity will have value 0,0,0
+    // If disable gravity, create a GravityEnabled component to the entity
     this->dataPtr->ecm->CreateComponent(
-        linkEntity, components::Gravity());
+        linkEntity, components::GravityEnabled(false));
   }
 
   // Visuals
diff --git a/src/systems/physics/Physics.cc b/src/systems/physics/Physics.cc
index c61279205f..687178a369 100644
--- a/src/systems/physics/Physics.cc
+++ b/src/systems/physics/Physics.cc
@@ -1161,21 +1161,12 @@ void PhysicsPrivate::CreateLinkEntities(const EntityComponentManager &_ecm)
         }
 
         // get link gravity
-        const components::Gravity *gravity =
-            _ecm.Component<components::Gravity>(_entity);
-        if (nullptr != gravity)
-        {
-          // Entity has a gravity component that is all zeros when
-          // <gravity> is set to false
-          // See SdfEntityCreator::CreateEntities()
-          if (gravity->Data() == math::Vector3d::Zero)
-          {
-            link.SetEnableGravity(false);
-          }
-          else
-          {
-            link.SetEnableGravity(true);
-          }
+        const components::GravityEnabled *gravityEnabled =
+            _ecm.Component<components::GravityEnabled>(_entity);
+        if (nullptr != gravityEnabled)
+        {
+          // gravityEnabled set in SdfEntityCreator::CreateEntities()
+          link.SetEnableGravity(gravityEnabled->Data());
         }
 
         auto linkPtrPhys = modelPtrPhys->ConstructLink(link);