[ros-users] Base Local Planner function visualization

Sun Dec 12 06:37:41 UTC 2010

On Tue, Dec 7, 2010 at 7:29 PM, Eitan Marder-Eppstein <
eitan at willowgarage.com> wrote:

> 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.
>

Took longer than I expected to get a chance to work on it, but I did finally
get a chance to change to using a boost::function and moving the visualizer
to TrajectoryPlannerROS. Changes are again available in my github repository
mentioned above.

I've also created a ticket to track getting this committed to the nav stack
(https://code.ros.org/trac/ros-pkg/ticket/4620) so that any further
discussion about the particulars can be discussed there.

- Eric

>
> 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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>>>>
>>>
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