Download Fuel models on the background

[chapulina]

When opening a world with models that have not been downloaded, there can be a long delay before the GUI opens.
It's also not possible to close gazebo while it's doing the initial download of models.

Desired behavior

While models are loading, the user should be able to interact with the window and close it if wanted.

Alternatives considered

I guess we could not open the window until the models are loaded, but that may be more confusing for users.

Implementation suggestion

• Download models in a separate thread
• Display models as they're downloaded
• Cancel loading if a signal is received
• Display status to user of what models are being loaded and what are missing
• Once we have a splash screen (Splash screen support gz-gui#336), we can use it to display this information

[ahcorde]

I have been working in this issue but I have some blockers. This is the branch of the current implementation https://github.com/ignitionrobotics/ign-gazebo/tree/ahcorde/download_background

• When I call Root::Load()

https://github.com/ignitionrobotics/ign-gazebo/blob/0e255a076c9063356c301e9d70118263051b3307/src/Server.cc#L168

I need to "fail" this call when there is a include tag because I launch a thread for each one of the include tag.

https://github.com/ignitionrobotics/ign-gazebo/blob/0e255a076c9063356c301e9d70118263051b3307/src/ServerPrivate.cc#L558-L561

The callback method will return an empty string making the Load method to fail, but when the thread has downloaded the resources are included. This is not problematic at all (we can filter the error in the load method), but when a include fails then I loose the pose and name, which are inside the include tag. But the model is not included because I force to fail to create the thread.

First question I don't know how to recover this data, is there any way to get this values ? the only idea that came to my mund is reloading the file again

This gif shows how models are downloaded in the background but without the right position and naming.

---

The other issue is about SDFs that define a geometry with an URI, this is still blocking the GUI. Like this one

 <model name="Radio">
      <pose>3 -1.5 0 0 0 0</pose>
      <static>true</static>
      <link name="link">
        <collision name="collision">
          <geometry>
            <mesh>
              <uri>https://fuel.ignitionrobotics.org/1.0/OpenRobotics/models/Radio/4/files/meshes/Radio.dae</uri>
            </mesh>
          </geometry>
        </collision>
        <visual name="visual">
          <geometry>
            <mesh>
              <uri>https://fuel.ignitionrobotics.org/1.0/OpenRobotics/models/Radio/4/files/meshes/Radio.dae</uri>
            </mesh>
          </geometry>
        </visual>
      </link>
    </model>

The model is downloaded in the same thread but for some reason this is blocking the runner

Question: I'm not really sure who might be blocking the runner. any thoughts?

---

This feature might include some changes in sdformat or/and fuel, Do you have any thoughts ?
@chapulina @scpeters @azeey

[scpeters]

when a include fails then I loose the pose and name, which are inside the include tag. But the model is not included because I force to fail to create the thread.

First question I don't know how to recover this data, is there any way to get this values ? the only idea that came to my mund is reloading the file again

This reminds me of the PreserveIncludes option in PrintConfig.hh (used in various libsdformat APIs for printing to strings) and also the ToElementUseIncludeTag option in OutputConfig.hh from gazebosim/sdformat#918 that is used to configure the ToElement() APIs.

• When I call Root::Load()

https://github.com/ignitionrobotics/ign-gazebo/blob/0e255a076c9063356c301e9d70118263051b3307/src/Server.cc#L168

I need to "fail" this call when there is a include tag because I launch a thread for each one of the include tag.

The callback method will return an empty string making the Load method to fail, but when the thread has downloaded the resources are included. This is not problematic at all (we can filter the error in the load method), but when a include fails then I loose the pose and name, which are inside the include tag. But the model is not included because I force to fail to create the thread.

I don't really understand all that is happening here