Add example launch & config for ease of use

[DoanNguyenTrong]

It took me a while to figure it out, so just want to share it with everybody.

[peci1]

Thank you for your contribution :+1: . Adding an example launch file that would run just robot_body_filter via sensor_filters is definitely a good idea.

However, it is not (yet) suitable for merging. There are several issues I see:

• The readme updates do not seem very informative; I'd rather add the note about the need for sensor_filters inside the example launch file, as there is no direct dependency between sensor_filters and robot_body_filter. You can write your own filter runner package, completely different from sensor_filters.
• The filter config has >75% commented lines. Please, clean it up and update the header of the file to actually reflect what robot do you run it on and with which sensor (e.g. the config says VLP-16, but you remap the points topic from /rslidar..., which would point to RoboSense). Please also try to express what is interesting on this filter config.
• The launch file should be moved to the examples folder, as well as the filter config file.
• The launch file contains a lot of unnecessary and distracting arguments. I would suggest removing most of them (keeping them at their defaults) (both their definitions and their use in the <include>). Keep description_name. This is an example file for public, so please do not try to use it directly (instead, keep your own copy/modification of the launch file in your own package). Files from the examples folder are not installed by CMake, so they are not available to those who use the binary distribution of this package.
• I suggest using $(dirname) in the launch file to reference to the config file instead of $(find robot_body_filter).
• Do not start topic names with slashes - it reduces reusability of the code.

[DoanNguyenTrong]

Hi @peci1, Sorry for my late response while you are extremely responsive. I sadly haven't had enough time, dive deep into the code to contribute more to this amazing project. All of the points that you mentioned are absolutely valid and I've fixed them in the last commit. Sorry for the bad content at the beginning.

Btw, if I want to remove points that are not in the URDF of my robot, but above the robot footprint, Can I do it and how (if possible)? Thanks

[peci1]

Sorry for my late response while you are extremely responsive.

No hurry, it was just coincidence ;)

Sorry for the bad content at the beginning.

Don't be sorry for it, you took a great job addressing my comments!

Btw, if I want to remove points that are not in the URDF of my robot, but above the robot footprint, Can I do it and how (if possible)?

Take a look at https://wiki.ros.org/pcl_ros/Tutorials/filters#PassThrough . But this filter can only cut by a plane or two planes, which might not be enough. There is also the undocumented CropBox filter which would probably be more suitable as it cuts out a box. But beware that it has problems with organized point clouds in Melodic. Unfortunately, all of these pcl_ros filters are not written using the filters API, but as a nodeletes, so you can't directly plug the pcl_ros filter alongside robot_body_filter in the YAML config file. I'm really thinking about sending a pull request to pcl_ros to fix this, but the repo seems mostly unmaintained, so it's not sure how fast (if ever) it will get merged.

---

Please, think through the frames/fixed and point_by_point setting as mentioned in the previous comment, and I think then this PR will be ready for merging.

[peci1]

Thank you for the contribution and patience!

[DoanNguyenTrong]

Learned a lot from you. Thanks and have joy with robots.