Add a min_obstacle_height param to the nav2_costmap_2d's ObstacleLaye…

…r plugin (ros-navigation#3211)

This allows considering full range observations, specified by the
  <data source>.min_obstacle_height
and
  <data source>.max_obstacle_height
especially used for the raytracing, but to still be able to specify a
minimum obstacle height to report obstacles onto the costmap.

This is in particular required in the case a PointCloud2 source points
slightly towards the ground, sometimes detecting obstacles, that should be
cleared once the ground reappears behind the obstacle when it has moved
away: we don't want to detect the ground as an obstacle, but still want it
to be used in the raytracing to clear the previously detected obstacle.

nav2_costmap_2d/include/nav2_costmap_2d/obstacle_layer.hpp

@@ -226,6 +226,7 @@ class ObstacleLayer : public CostmapLayer
     double * max_y);
 
   std::string global_frame_;  ///< @brief The global frame for the costmap
+  double min_obstacle_height_;  ///< @brief Max Obstacle Height
   double max_obstacle_height_;  ///< @brief Max Obstacle Height
 
   /// @brief Used to project laser scans into point clouds

nav2_costmap_2d/plugins/obstacle_layer.cpp

@@ -78,6 +78,7 @@ void ObstacleLayer::onInitialize()
 
   declareParameter("enabled", rclcpp::ParameterValue(true));
   declareParameter("footprint_clearing_enabled", rclcpp::ParameterValue(true));
+  declareParameter("min_obstacle_height", rclcpp::ParameterValue(0.0));
   declareParameter("max_obstacle_height", rclcpp::ParameterValue(2.0));
   declareParameter("combination_method", rclcpp::ParameterValue(1));
   declareParameter("observation_sources", rclcpp::ParameterValue(std::string("")));
@@ -89,6 +90,7 @@ void ObstacleLayer::onInitialize()
 
   node->get_parameter(name_ + "." + "enabled", enabled_);
   node->get_parameter(name_ + "." + "footprint_clearing_enabled", footprint_clearing_enabled_);
+  node->get_parameter(name_ + "." + "min_obstacle_height", min_obstacle_height_);
   node->get_parameter(name_ + "." + "max_obstacle_height", max_obstacle_height_);
   node->get_parameter(name_ + "." + "combination_method", combination_method_);
   node->get_parameter("track_unknown_space", track_unknown_space);
@@ -296,7 +298,9 @@ ObstacleLayer::dynamicParametersCallback(
     const auto & param_name = parameter.get_name();
 
     if (param_type == ParameterType::PARAMETER_DOUBLE) {
-      if (param_name == name_ + "." + "max_obstacle_height") {
+      if (param_name == name_ + "." + "min_obstacle_height") {
+        min_obstacle_height_ = parameter.as_double();
+      } else if (param_name == name_ + "." + "max_obstacle_height") {
         max_obstacle_height_ = parameter.as_double();
       }
     } else if (param_type == ParameterType::PARAMETER_BOOL) {
@@ -453,6 +457,12 @@ ObstacleLayer::updateBounds(
     for (; iter_x != iter_x.end(); ++iter_x, ++iter_y, ++iter_z) {
       double px = *iter_x, py = *iter_y, pz = *iter_z;
 
+      // if the obstacle is too low, we won't add it
+      if (pz < min_obstacle_height_) {
+        RCLCPP_DEBUG(logger_, "The point is too low");
+        continue;
+      }
+
       // if the obstacle is too high or too far away from the robot we won't add it
       if (pz > max_obstacle_height_) {
         RCLCPP_DEBUG(logger_, "The point is too high");