System Plugin Intefaces¶

official gazebo sim doc link

comman line in any system plugin

class MoveModel :
    // This class is a system.
    public gz::sim::System,
    public gz::sim::ISystemConfigure,
    public gz::sim::ISystemPreUpdate,
    //public gz::sim::ISystemUpdate,
    //public gz::sim::ISystemPostUpdate

// Register the plugin with Gazebo Sim
GZ_ADD_PLUGIN(gz::sim::systems::MoveModel,
              gz::sim::System,
              gz::sim::ISystemConfigure,
              gz::sim::ISystemPreUpdate)

Note: in inheriting which class what function needs to be defined

• gz::sim::ISystemConfigure -> Configure()
• gz::sim::ISystemPreUpdate -> PreUpdate()
• public gz::sim::ISystemUpdate -> Update()
• public gz::sim::ISystemPostUpdate -> PostUpdate()

void Configure(const Entity &_entity,
                   const std::shared_ptr<const sdf::Element> &_sdf,
                   EntityComponentManager &_ecm,
                   EventManager &_eventMgr) override;

void PreUpdate(const UpdateInfo &_info,
                  EntityComponentManager &_ecm) override;

void Update(const UpdateInfo &_info, EntityComponentManager &_ecm) override;

void PostUpdate(const UpdateInfo &_info, const EntityComponentManager &_ecm) override;  

class api: ISystemConfigure,ISystemPreUpdate,ISystemUpdate, ISystemPostUpdate

all of the above are pure virtual funtion because of which all need to defined in the derive class

Decide on interfaces to implement¶

The first step of implementing a system plugin is to determine the subset of available interfaces to implement. Aside from the base System object, there are currently four additional available interfaces:

1. ISystemConfigure
   
   • read-write access
   • Executed once
   • SDF file parameters define
     
2. ISystemPreUpdate
   • read-write access
   • modify state before physics runs
     
3. ISystemUpdate
   
   • read-write access
   • Used for physics simulation step (i.e., simulates what happens at time gz::sim::UpdateInfo::simTime).
     
4. ISystemPostUpdate
   
   • read-only access
   • Used to read out results at the end of a simulation step to be used for sensor or controller updates.
     
5. ISystemReset
   
   • read-write access
   • Executed once the moment the plugin is reseted.