Added reset simulation tutorial

examples/plugin/system_plugin/SampleSystem.hh

@@ -45,7 +45,8 @@ namespace sample_system
     // and ISystemPostUpdate interfaces.
     public gz::sim::ISystemPreUpdate,
     public gz::sim::ISystemUpdate,
-    public gz::sim::ISystemPostUpdate
+    public gz::sim::ISystemPostUpdate,
+    public gz::sim::ISystemReset
   {
     public: SampleSystem2();
 
@@ -59,6 +60,9 @@ namespace sample_system
 
     public: void PostUpdate(const gz::sim::UpdateInfo &_info,
                 const gz::sim::EntityComponentManager &_ecm) override;
+
+    public: void Reset(const gz::sim::UpdateInfo &_info,
+                 gz::sim::EntityComponentManager &_ecm) override;
   };
 }
 //! [header]

examples/plugin/system_plugin/SampleSystem2.cc

@@ -8,7 +8,8 @@ GZ_ADD_PLUGIN(
     gz::sim::System,
     sample_system::SampleSystem2::ISystemPreUpdate,
     sample_system::SampleSystem2::ISystemUpdate,
-    sample_system::SampleSystem2::ISystemPostUpdate)
+    sample_system::SampleSystem2::ISystemPostUpdate,
+    sample_system::SampleSystem2::ISystemReset)
 //! [registerSampleSystem2]
 
 using namespace sample_system;
@@ -38,3 +39,9 @@ void SampleSystem2::PostUpdate(const gz::sim::UpdateInfo &_info,
 {
   gzmsg << "SampleSystem2::PostUpdate" << std::endl;
 }
+
+void SampleSystem2::Reset(const gz::sim::UpdateInfo &_info,
+     gz::sim::EntityComponentManager &_ecm)
+{
+  gzmsg << "SampleSystem2::Reset" << std::endl;
+}

tutorials.md.in

@@ -42,6 +42,7 @@ Gazebo @GZ_DESIGNATION_CAP@ library and how to use the library effectively.
 * \subpage spherical_coordinates "Spherical coordinates": Working with latitude and longitude
 * \subpage python_interfaces Python interfaces
 * \subpage headless_rendering "Headless rendering": Access the GPU on a remote machine to produce sensor data without an X server.
+* \subpage reset_simulation Reset simulation
 * \subpage move_camera_to_model Move camera to model
 
 **Migration from Gazebo classic**

tutorials/create_system_plugins.md

@@ -15,8 +15,8 @@ steps below.
 ## 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 three additional available interfaces:
+available interfaces to implement. Aside from the base `System` object,
+there are currently four additional available interfaces:
 
 1. ISystemConfigure
   1. Has read-write access to world entities and components.
@@ -27,13 +27,16 @@ there are currently three additional available interfaces:
   1. Has read-write access to world entities and components.
   2. This is where systems say what they'd like to happen at time gz::sim::UpdateInfo::simTime.
   3. Can be used to modify state before physics runs, for example for applying control signals or performing network synchronization.
-2. ISystemUpdate
+3. ISystemUpdate
   1. Has read-write access to world entities and components.
   2. Used for physics simulation step (i.e., simulates what happens at time gz::sim::UpdateInfo::simTime).
-3. ISystemPostUpdate
+4. ISystemPostUpdate
   1. Has read-only access to world entities and components.
   2. Captures everything that happened at time gz::sim::UpdateInfo::simTime.
   3. Used to read out results at the end of a simulation step to be used for sensor or controller updates.
+5. ISystemReset
+  1. Has read-write access to world entities and components.
+  2. Executed once the moment the plugin is reseted.
 
 It's important to note that gz::sim::UpdateInfo::simTime does not refer to the current time, but the time reached after the `PreUpdate` and `Update` calls have finished.
 So, if any of the `*Update` functions are called with simulation paused, time does not advance, which means the time reached after `PreUpdate` and `Update` is the same as the starting time.

tutorials/reset_simulation.md

@@ -0,0 +1,31 @@
+\page reset_simulation Reset simulation
+
+The Reset Gazebo transport API is exposed to allow resetting simulation to time zero.
+It's possible to call this API using the command line or through the GUI.
+In addition to the API, we have also expanded the simulation system API with a Reset interface.
+
+# Reset interface
+
+System authors may now choose to implement the Reset interface to have a more intelligent
+reset process (avoiding reloading assets or regenerating scene graphs being the motivating examples).
+Since this interface is opt-in, systems that don't implement the API will still be reset via destruction and reconstruction.
+The [physics](https://github.com/gazebosim/gz-sim/blob/gz-sim7/src/systems/physics/Physics.cc#L928-L937) and [rendering systems](https://github.com/gazebosim/gz-sim/blob/gz-sim7/src/systems/scene_broadcaster/SceneBroadcaster.cc#L452-L458) are the first two to implement this optimized reset functionality, with more to come as it makes sense to.
+
+Following the tutorial \subpage createsystemplugins we should implement `ISystemReset` interface.
+
+# Transport API
+
+To call the reset transport API we should call the service `/world/default/control` and fill the request message type
+`gz.msgs.WorldControl`, this service return a `gz.msgs.Boolean` with the status of the reset (true is everything was fine, false otherwise)
+
+The `WorldControl` message now contains a reset field that we should filled if we want to reset the world:
+
+```bash
+gz service -s /world/default/control --reqtype gz.msgs.WorldControl --reptype gz.msgs.Boolean --timeout 3000 --req 'reset: {all: true}'
+```
+
+# GUI
+
+We included a new button in the `World Control` plugin allowing to reset the simulation from the GUI
+
+@image html files/reset_simulation/reset_button.gif