will the parameter padded_footprint_ be increased with the cycles? [closed]

edit

in costmap_2d_ros.cpp,when we call the function updateMap(),it will publish the footprint with the cycle,and then,we will always call the funtcion setUnpaddedRobotFootprintPolygon().is that right?

and I found that the parameter padded_footprint_ will be increase with the cycle under the influence of the function transformFootprint() in footprint.cpp here is the code and the function setUnpaddedRobotFootprint() in costmap_2d_ros.cpp code .Did I misunderstand?

I actually don't know why we need to transform footprint