How to "paint" spots robot visited in Gazebo?

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You can try to implement your own Gazebo plugins (C++):

• https://classic.gazebosim.org/tutoria...
• https://classic.gazebosim.org/tutoria...
• https://www.youtube.com/watch?v=JJDeb...
• https://www.youtube.com/playlist?list... (list of video tutorials, step by step)

I can see two plugins or a plugin + a timer node there:

• 1) (plugin/node) It should modify a PNG file, basing on the robot localization every N seconds, "painting" a path on the surface,

• 2) (plugin) Update visuals of the floor by loading aforementioned PNG file as its texture every few seconds.

A "hackish" way in Python would be spawning a static objects (a tile?) without collision boxes right under the robot, below the surface, with a bright color, every N seconds. It has some problems thought (many objects in the world after a while etc.). You could work it out thought, e.g. delete the overlapped boxes and swap them with one bigger tile etc.

I have seen no pre-packaged way to do what you ask for.

I would think twice before implementing this in a gazebo-specific way. The problem is that it will work only in simulation (and will not work when running a real robot.) I'd look for a solution that works for both cases.

Probably the simplest programming approach for someone new to ros would be to create a python ros node which opens a graphical image window using the opencv API. The idea is to treat this window as a 2D grid. Load your map into the window, scaling it if necessary. Subscribe to your robot's pose topic. For each pose message you receive, color the corresponding grid x,y in the window.

There is a conceptually similar approach that would use rviz for the display by creating a custom layer for the global costmap, but this requires using c++, and the API's have a steeper learning curve than opencv has. This approach is not for beginners.