Update documentation about getting the pose of the trackers without the headsets

[HosameldinMohamed]

In addition to the use case described in https://github.com/ami-iit/yarp-openvr-trackers/blob/cd153dbb2c9a6c5056cf13bd74865c7b14850f1a/README.md#checking-the-hardware-setup
It is possible to get the trackers poses without the need for a headset.

See (https://vvvv.org/blog/using-htc-vive-trackers-without-headset) and (https://www.roadtovr.com/how-to-use-the-htc-vive-tracker-without-a-vive-headset/).

The steps are:

• When launching SteamVR without connecting a headset, it will complain saying there's no headset connected, then following the steps below, we can configure Steam to ignore the headset:

  • Enabling the null driver: Opening the file <steam-files-location>/steam/steamapps/common/SteamVR/drivers/null/resources/settings/default.vrsettings and setting enable to true.
  • Opening the file <steam-files-location>/steam/steamapps/common/SteamVR/resources/settings/default.vrsettings and setting requireHmd to false, forcedDriver to null, and activateMultipleDrivers to true.
  • Opening the file <steam-files-location>/steam/config/steamvr.vrsettings and setting requireHmd to false, forcedDriver to null, and activateMultipleDrivers to true (add if not present inside section steamvr).

• Close and open SteamVR, it should open another window that mimics the headsetVR. Connect the USB dongle and start pairing the trackers.

• After successful pairing and while also connecting a base-station (at least one), the interface of SteamVR should look like this:
  

• For a quick test, using the Python application in https://github.com/TriadSemi/triad_openvr.

  • Run pip install openvr.
  • inside the cloned repo run with Python triad_openvr/tracker_test.py. You should see the pose information printed online.