HAPTIX logging

Overview

This tutorial will explain how to use the Gazebo logging capabilities for saving your simulation episode on disk and being able to reproduce it afterwards.

We assume that you have already done the installation step and you are also familiar with the HAPTIX API.

A Gazebo log file

A Gazebo log file is a collection of State logs. State logs are recordings of world state information from Gazebo. State includes pose, velocity, acceleration, and forces applied to all links of all models. Gazebo will only record state information for models that change over time. A state log file contains a header, the initial world description, and a time series of state.

Enable Gazebo logging from the GUI

Start Gazebo and click on the top right icon of the menu bar when you are ready to start your logging.

A new pop-up window will appear. Click on the red record button to start the log. Click on the same icon again when needed to stop logging.

A new time stamped directory should exist in ~/.gazebo/log with one subdirectory and a state.log file. Here is an example:

~/.gazebo/log/2013-07-25T07\:29\:05.122275/gzserver/state.log

Enable Gazebo logging from your C++ program

Follow the steps described in the HAPTIX C-API tutorial for compiling a program using your favorite operating system.

Uncomment the following blocks to enable logging:

// Uncomment this block to start logging.
// if (hxs_start_logging("/tmp") != hxOK)
//   printf("hxs_start_logging(): error.\n");

and:

// Uncomment this block to stop logging.
// if (hxs_stop_logging() != hxOK)
//   printf("hxs_stop_logging(): error.\n");

When executed, this example should create a /tmp/log/ directory containing a state.log file.

Enable Gazebo logging from your MATLAB/Octave program

Follow the HAPTIX Matlab and Octave API tutorial and load the hx_matlab_controller in Octave or MATLAB.