RNDF file path in World file

[Agustin Alba Chicar]

We need to change the file path of the RNDF file in the world file description, insde the plugin node, to use a relative path to the world file path.

[Agustin Alba Chicar]

@JChoclin @andres_fortier, reading the docs of Gazebo it has some predefined environment variables for this purpose. I think we should source the script <install_path>/share/gazebo/setup.sh this file in our docker image. Besides that, after sourcing that file, I think we can update the variable GAZEBO_RESOURCE_PATH with our samples directory from terminus and this repository for getting just the file names in the world samples. We should explain this in the README too. This is process is already done with the GAZEBO_PLUGIN_PATH variable. This change was introduced in this commit.

[Agustin Alba Chicar]

@JChoclin @andres_fortier, researching in code a bit, we have an API provided by Gazebo to find files and retrieve the environment variables in code. This interface is provided in our Gazebo version too.

[Andrés Fortier]

I would try to keep this as much "Gazebo standard" as possible. From the docs it seems that GAZEBO_RESOURCE_PATH is the place where we should be putting the RNDFs, so that responsibility is on the user (we should however mention that in the README). Does that make sense to you? I would avoid wasting time on trying to append a new path to it, just make it clear to the user that this is the place where the rndf should go.

[Agustin Alba Chicar]

Indeed, it works that way.

[Javier Iván Choclin]

Included the file search inside the gazebo paths for the RNDF files. refs #53

→ <<cset 5a3cace01fde>>

[Javier Iván Choclin]

Added source gazebo env to readme. refs #53

→ <<cset beb67ba8dcc5>>

[Javier Iván Choclin]

After rebase code refactor. refs #53

→ <<cset 0560e79d139f>>