Is path valid doc (ros-navigation#4032)

* docs

Signed-off-by: gg <[email protected]>

* update

Signed-off-by: gg <[email protected]>

---------

Signed-off-by: gg <[email protected]>

Author: jwallace42

nav2_planner/src/planner_server.cpp

@@ -644,7 +644,8 @@ void PlannerServer::isPathValid(
 
     /**
      * The lethal check starts at the closest point to avoid points that have already been passed
-     * and may have become occupied
+     * and may have become occupied. The method for collision detection is based on the shape of 
+     * the footprint. 
      */
     std::unique_lock<nav2_costmap_2d::Costmap2D::mutex_t> lock(*(costmap_->getMutex()));
     unsigned int mx = 0;