I've been struggling with these problem for days. the idea is to generate a layered Costmap that is valid for different multi-robot-system formation. The first challenge is that the units recognizing each other as obstacles, so i created a layer that comes between the obstacle and inflation layer, the idea of this layer is to clear all the footprints of each robot. As shown in RVIZ, there is always cells left behind and not cleared, and they only show up after the formation is passed by. Here is the costmap of the leader robot, leaving obstacle points behind the two other robots that only appear after passing by: