add plugin to publish TF between two links attached to the same model

CMakeLists.txt

@@ -101,6 +101,7 @@ set(LIBRARIES
   MrsGazeboCommonResources_FluidResistancePlugin
   MrsGazeboCommonResources_MotorSpeedRepublisherPlugin
   MrsGazeboCommonResources_MotorPropModelPlugin
+  MrsGazeboCommonResources_LinkStaticTFPublisher
   )
 
 catkin_package(
@@ -371,6 +372,18 @@ target_link_libraries(MrsGazeboCommonResources_MotorPropModelPlugin
   ${Boost_LIBRARIES}
   )
 
+# LinkStaticTFPublisher
+
+add_library(MrsGazeboCommonResources_LinkStaticTFPublisher SHARED
+  src/sensor_and_model_plugins/link_static_tf_publisher.cpp
+  )
+
+target_link_libraries(MrsGazeboCommonResources_LinkStaticTFPublisher
+  ${GAZEBO_LIBRARIES}
+  ${catkin_LIBRARIES}
+  ${Boost_LIBRARIES}
+  )
+
 ## --------------------------------------------------------------
 ## |                           Install                          |
 ## --------------------------------------------------------------

src/sensor_and_model_plugins/link_static_tf_publisher.cpp

@@ -0,0 +1,82 @@
+/* Mostly generated using ChatGPT 3.5 */
+
+#include <gazebo/common/Plugin.hh>
+#include <gazebo/common/common.hh>
+#include <gazebo/physics/physics.hh>
+#include <ros/ros.h>
+#include <tf2_msgs/TFMessage.h>
+#include <tf2/LinearMath/Quaternion.h>
+#include <tf2_ros/static_transform_broadcaster.h>
+
+namespace gazebo
+{
+
+class LinkStaticTFPublisher : public ModelPlugin {
+private:
+  physics::ModelPtr                   model;
+  tf2_ros::StaticTransformBroadcaster tf_broadcaster;
+
+public:
+  LinkStaticTFPublisher() {
+  }
+
+  virtual void Load(physics::ModelPtr _model, sdf::ElementPtr _sdf) {
+    // Safety check
+    if (!_model) {
+      ROS_ERROR("[LinkStaticTFPublisher]: Invalid model pointer!");
+      return;
+    }
+
+    model = _model;
+
+    std::string parentLinkName;
+    std::string childLinkName;
+
+    if (_sdf->HasElement("parentLink")) {
+      parentLinkName = _sdf->Get<std::string>("parentLink");
+    }else{
+      ROS_ERROR("[LinkStaticTFPublisher]: SDF is missing element \"parentLink\"");
+      return;
+    }
+
+    if (_sdf->HasElement("childLink")) {
+      childLinkName = _sdf->Get<std::string>("childLink");
+    }else{
+      ROS_ERROR("[LinkStaticTFPublisher]: SDF is missing element \"childLink\"");
+      return;
+    }
+
+    // Get pointers to the specified parent and child links
+    physics::LinkPtr parentLink = model->GetLink(parentLinkName);
+    physics::LinkPtr childLink  = model->GetLink(childLinkName);
+
+    // Check if both links are valid
+    if (!parentLink || !childLink) {
+      ROS_ERROR_STREAM("[LinkStaticTFPublisher]: One or both of the links \"" << parentLinkName << "\", \"" << childLinkName << "\" do not exist!");
+      return;
+    }
+
+    // Get the transform between the parent and child links
+    ignition::math::Pose3d relativePose = childLink->WorldPose() - parentLink->WorldPose();
+
+    tf2::Quaternion quat(relativePose.Rot().X(), relativePose.Rot().Y(), relativePose.Rot().Z(), relativePose.Rot().W());
+
+    // Publish the transform
+    geometry_msgs::TransformStamped transformStamped;
+    transformStamped.header.stamp            = ros::Time::now();
+    transformStamped.header.frame_id         = parentLinkName;
+    transformStamped.child_frame_id          = childLinkName;
+    transformStamped.transform.translation.x = relativePose.Pos().X();
+    transformStamped.transform.translation.y = relativePose.Pos().Y();
+    transformStamped.transform.translation.z = relativePose.Pos().Z();
+    transformStamped.transform.rotation.w    = relativePose.Rot().W();
+    transformStamped.transform.rotation.x    = relativePose.Rot().X();
+    transformStamped.transform.rotation.y    = relativePose.Rot().Y();
+    transformStamped.transform.rotation.z    = relativePose.Rot().Z();
+    tf_broadcaster.sendTransform(transformStamped);
+    ROS_INFO_STREAM("[LinkStaticTFPublisher]: Published static TF between frames \"" << parentLinkName << "\", \"" << childLinkName << "\"");
+  }
+};
+
+GZ_REGISTER_MODEL_PLUGIN(LinkStaticTFPublisher)
+}  // namespace gazebo