Logging

The logging system allows for recording and playing back world state information. Currently, only link poses are supported. In the future, other state information will be supported.

Record from command line

Run the example world with --record flag. This records data to a default path, i.e. ~/.ignition/gazebo/log/<timestamp>:

ign gazebo -v 4 -r --record pose_publisher.sdf

A custom path can be specified for recorded files through the --record-path flag. When --record-path is specified, --record does not need to be separately specified:

ign gazebo -v 4 -r --record-path ./foo pose_publisher.sdf

Record by specifying plugin in SDF

Recording can be specified in the SDF, under <world> tag:

<world name="default">
    ...
    <plugin
      filename="libignition-gazebo-log-system.so"
      name="ignition::gazebo::systems::LogRecord">
      
      <path>/tmp/log</path>
    </plugin>
    ...
</world>

If <path> is not specified, recorded files will be placed in the default path (~/.ignition/gazebo/log/<timestamp>).

Currently, it is enforced that only one recording instance is allowed to start during a Gazebo run.

Note

If both a record plugin and a record command line flag are specified, e.g. ign gazebo -v 4 -r --record log_record_shapes.sdf, the command line flag will be ignored, and recorded files will be placed in the path specified in the plugin SDF (or default if none specified).

Playback from command line

Playback can be triggered by --playback command line flag. <path> is the directory specified to record:

ign gazebo -r -v 4 --playback <path>

Playback by specifying plugin in SDF

Alternatively, playback can be specified in an SDF file. See example file examples/worlds/log_playback.sdf:

<world name="default">
    ...
    <plugin
      filename='libignition-gazebo-log-system.so'
      name='ignition::gazebo::systems::LogPlayback'>
      <path>/tmp/log</path>
    </plugin>
    ...
</world>

Note

The physics plugin should not be specified in the SDF. If specified, it will be automatically removed so that physics does not clash with the recorded poses.

If both a world file <file> and --playback <path> are specified, an error is printed. This is not allowed, because the world file may be a very different world from the one that was recorded.

Known issues

• When using command-line playback there is currently a small caveat. In the case that the recorded file uses ogre2, the playback appears brighter, because the default SDF that is loaded by Server.cc for playback uses ogre.
• Currently, specifying record and playback at the same time is not allowed. We may support this in the future, to support cropping a recording or changing the encoding.