[ros-users] Base Local Planner function visualization

Wed Dec 8 00:29:16 UTC 2010

Eric,

On Tue, Dec 7, 2010 at 3:27 PM, Eric Perko <wisesage5001 at gmail.com> wrote:

> Eitan,
>
> On Tue, Dec 7, 2010 at 1:43 PM, Eitan Marder-Eppstein <
> eitan at willowgarage.com> wrote:
>
>> Eric,
>>
>> First off, this is awesome! Its a great tool that I'd love to take back to
>> the navigation stack. To make it more useful for other local planners, it
>> might be nice to have the MapGridVisualizer take in something like a
>> boost::function or function ptr for computing the cost of a given cell. It
>> could call that function with x and y map coordinates and get back
>> goal_cost, path_cost, occ_cost, and total_cost. This would also mean that we
>> might get away with not making the MapGrid for the planners public. Instead,
>> each planner that wants to publish this information just implements this
>> function that the MapGridVisualizer can call. Another option would be to add
>> such a function to the BaseLocalPlanner interface instead, but requiring a
>> planner to implement it makes a lot of assumptions about the way it works
>> and I don't think it belongs there.
>>
>
> I like the idea of just providing a way for a local planner to basically
> register an arbitrary cost function with the visualizer. Heck, it would even
> be a quick and easy way to prototype new cost functions and see what sort of
> effects they have on the potential field. I'll play around with this tonight
> or tomorrow and see how it goes. Thanks for the idea.
>

Sounds good. Let me know when you've got something and I'll take a look at
it.

Hope all is well,

Eitan

>
>
>> Let me know what you think, and thanks for passing this along, definitely
>> cool,
>>
>
> Glad you also think it will be useful :)
>
> - Eric
>
>
>>
>> Eitan
>>
>> On Mon, Dec 6, 2010 at 11:30 PM, Eric Perko <wisesage5001 at gmail.com>wrote:
>>
>>> Hey all,
>>>
>>> So, last time I worked with tuning the cost scoring parameters of
>>> base_local_planner it was tricky due to no way to easily tell how each term
>>> in the cost function was influencing the scored trajectories. To address
>>> this problem, I've created a class that outputs a PointCloud2 on a topic
>>> called cost_cloud under the base_local_planner namespace that contains the
>>> cost information for each component of the cost function as well as the
>>> total cost for each point the MapGrid maintained by the TrajectoryPlanner
>>> class. You can find the code here:
>>> https://github.com/ericperko/ros_navigation . You can find some sample
>>> images from rviz at
>>> http://www.dropbox.com/gallery/1970299/1/BaseLocalPlannerVizSamples?h=885d40 ,
>>> files named by which cost value they are visualizing (hover over the
>>> thumbnails to see the filenames or click for the gallery view and it will be
>>> listed below the thumbnails at the top), to give you all an idea of what
>>> this code outputs (red is lowest cost).
>>>
>>> There are a few steps to actually being able to use this functionality:
>>>
>>>
>>>    1. Checkout the updated Nav Stack from
>>>    https://github.com/ericperko/ros_navigation or otherwise apply
>>>    commit
>>>    https://github.com/ericperko/ros_navigation/commit/00ec9847100942767a80524b401fc8c26e652d02 to
>>>    your existing base_local_planner package & recompile it.
>>>    2. Update your base_local_planner_params.yaml file with two more
>>>    parameters:
>>>       1. "publish_cost_grid_pc" to true. Default is false so that people
>>>       who aren't interested in seeing the point cloud aren't wasting cycles making
>>>       & publishing it.
>>>       2. "global_frame_id" to whatever your local costmap's global frame
>>>       is. By default, this is "odom" to match the setup in the nav stack setup (
>>>       http://www.ros.org/wiki/navigation/Tutorials/RobotSetup ). This is
>>>       the frame id set for the output point cloud so will determine how it draws
>>>       in the map.
>>>    3. Now you should be able to verify that base_local_planner is
>>>    outputting a PointCloud using something like "rostopic hz
>>>    /move_base/TrajectoryPlannerROS/cost_cloud"
>>>    4. In order to visualize the PointCloud in a meaningful way, you will
>>>    have to apply the patch in
>>>    https://code.ros.org/trac/ros-pkg/ticket/4610 to RViz so that you can
>>>    treat arbitrary channels as intensity data. The visualization will be much
>>>    more readable if you also make sure to check the "Use full RGB spectrum" box
>>>    so that gradients are more apparent.
>>>    5. Have fun selecting different components of the cost function and
>>>    seeing what sort of affect they have on the potential field that
>>>    base_local_planner is sampling trajectories from! Note that we don't output
>>>    any points that have any cost component greater than max cost and would
>>>    therefore be illegal for the planner to try to execute.
>>>
>>> Feedback would be very welcome and I hope this comes in handy. I know
>>> it's already helped me out by letting me see that my obstacle cost field
>>> doesn't extend as far as I might like.
>>>
>>>  Eitan, any feedback on changes that are required to make this more
>>> general for use in, for example, dwa_local_planner would be great. Also, the
>>> C++ API of TrajectoryPlanner would likely have to change slightly if we
>>> wanted to move the visualizer and it's use of ROS topics and parameters up
>>> to TrajectoryPlannerROS. Specifically, the MapGrid would either need to
>>> become public or we'd need to add a getter for it; currently it's private to
>>> the TrajectorPlanner, so that's where the MapGridVisualizer is instantiated.
>>> Either that or pass in a number of variables in the constructor/setter
>>> methods (especially the scaling values). Let me know what you think would be
>>> the best idea for improving it, as I was currently going for a minimally
>>> invasive patch to start with and would like to get a more finalized patch
>>> together before opening a ticket to add this to the nav_stack.
>>>
>>> - Eric
>>>
>>> _______________________________________________
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>>> ros-users at code.ros.org
>>> https://code.ros.org/mailman/listinfo/ros-users
>>>
>>>
>>
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