in costmap2dros.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 paddedfootprint 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 costmap2dros.cpp code .Did I misunderstand?

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