## repository: https://code.ros.org/svn/ros-pkg
<<PackageHeader(navfn)>>

<<TOC(4)>>

== Overview ==
This package provides an implementation of a fast, interpolated navigation function used to create plans for a mobile base through the `navfn::NavFn` class. It also provides a [[navigation/ROS_Wrappers | ROS Wrapper]] for this class via the `navfn::NavfnROS` object that adheres to the `nav_core::BaseGlobalPlanner` interface specified in the [[nav_core]] package. The `navfn::NavfnROS` object is also used as a global planner plugin for the [[move_base]] node.

== NavfnROS ==
The `navfn::NavfnROS` object is a [[navigation/ROS_Wrappers | wrapper]] for a `navfn::NavFn` object that exposes its functionality as a [[navigation/ROS_Wrappers | C++ ROS Wrapper]]. It operates within a ROS namespace (assumed to be ''name'' from here on) specified on initialization. It adheres to the `nav_core::BaseGlobalPlanner` interface found in the [[nav_core]] package.

Example creation of a `navfn::NavfnROS` object:

{{{
#!cplusplus
#include <tf/transform_listener.h>
#include <costmap_2d/costmap_2d_ros.h>
#include <navfn/navfn_ros.h>

...

tf::TransformListener tf(ros::Duration(10));
costmap_2d::Costmap2DROS costmap("my_costmap", tf);

navfn::NavfnROS navfn;
navfn.initialize("my_navfn_planner", &costmap);
}}}

=== API Stability ===
 * The ROS API is stable
 * The C++ API is stable

=== ROS API ===
{{{
#!clearsilver CS/NodeAPI
pub {
  0.name  = ~<name>/plan
  0.type = nav_msgs/Path
  0.desc = The last plan computed by `navfn`, published everytime the planner computes a new path, and used primarily for visualization purposes.
}
param {
  0.name = ~<name>/allow_unknown
  0.default = `true`
  0.type = bool
  0.desc = Specifies whether or not to allow navfn to create plans that traverse unknown space.  NOTE: if you are using a layered costmap_2d costmap with [[costmap_2d/hydro/obstacles|a voxel or obstacle layer]], you must also set the track_unknown_space param for that layer to be true, or it will convert all your unknown space to free space (which navfn will then happily go right through).
  1.name = ~<name>/planner_window_x
  1.default = 0.0
  1.type = double
  1.desc = Specifies the x size of an optional window to restrict the planner to. This can be useful for restricting !NavFn to work in a small window of a large costmap.
  2.name = ~<name>/planner_window_y
  2.default = 0.0
  2.type = double
  2.desc = Specifies the y size of an optional window to restrict the planner to. This can be useful for restricting !NavFn to work in a small window of a large costmap.
  3.name = ~<name>/default_tolerance
  3.default = 0.0
  3.type = double
  3.desc = A tolerance on the goal point for the planner. NavFn will attempt to create a plan that is as close to the specified goal as possible but no further than `default_tolerance` away. '''New in navigation 1.3.0'''
  4.name = ~<name>/visualize_potential
  4.default = `false`
  4.type = bool
  4.desc = Specifies whether or not to visualize the potential area computed by navfn via a !PointCloud2. '''New in navigation 1.3.1'''
}
}}}

=== C++ API ===
`navfn::NavfnROS` adheres to the `nav_core::BaseGlobalPlanner` interface found in the [[nav_core]] package. For detailed documentation, please see [[http://www.ros.org/doc/api/navfn/html/classnavfn_1_1NavfnROS.html | NavfnROS C++ Documentation]].

== NavFN ==
The `navfn::NavFn` object provides an implementation of the navigation function described above. Feel free to use it, but beware that we make no guarantees about the stability of its public API.

=== API Stability ===
 * The C++ API is '''not''' stable. It is subject to change at any time.

=== C++ API ===
 Documentation on the C++ API for the `navfn::NavFn` class can be found here: [[http://www.ros.org/doc/api/navfn/html/classnavfn_1_1NavFn.html | NavFn Documentation]]. Again, the C++ API is '''not''' guaranteed to be stable.

== Reference ==
 * [[http://answers.ros.org/question/28366/why-navfn-is-using-dijkstra|Rationale of Dijkstra being used in navfn instead of A*]]

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