Armin,

Right now, navfn requires that the start and the goal map to the center of a grid cell for planning. Propagation of the potential function will always be done assuming cells of some resolution, however, I suppose we could start walking the gradient from a non-centered cell coordinate which could make a fair amount of difference if you're talking about a large cell size in your gird. I filed a ticket to do this here: https://code.ros.org/trac/ros-pkg/ticket/4001.

I've got some other stuff going on right now, but I'll try to get to this when I can... hopefully in the next week or so.

Thanks again for pointing these things out, its been quite helpful.

Hope all is well,

Eitan

On Fri, Apr 16, 2010 at 3:13 AM, Armin Hornung <HornungA@informatik.uni-freiburg.de> wrote:
Hi Eitan!

Thanks so much for finding this, I've fixed the bug in both trunk (rev
28749) and the 1.0 branch (rev 28750) of navigation and the fixes will go
out with the next patch release of both the 1.0 and the 1.1 series. I'll try
to push out patch releases either later today or tomorrow and I believe it
should fix the problem you're seeing.
 

I had a look at the fixed navfn now, and the paths indeed look a lot nicer and smoother now. Thanks!

Now only the strange behavior at the start and the end of a path remain, as seen in the attached screenshot. It seems like the computed path starts and ends at the top right grid cell center of the actual start and goal position, with an added (unsmooth) path segment from the computed goal to the requested one. The effect is of course more pronounced in larger grid resolutions (and also happend in my empty test case map). Is that something fixable in the navfn code?

If it's only possible to plan on grid cell centers, a workaround could be to start and end the computed path on the grid cell that is between the actual (requested) goal and start and then adding a first and last segment which extends the computed path in a similar direction. That should cause a less discontinuous curve.


Cheers,
Armin

--
Armin Hornung                              Albert-Ludwigs-Universität
www.informatik.uni-freiburg.de/~hornunga   Dept. of Computer Science
HornungA@informatik.uni-freiburg.de        Humanoid Robots Lab
Tel.: +49 (0)761-203-8010                  Georges-Köhler-Allee 79
Fax : +49 (0)761-203-8007                  D-79110 Freiburg, Germany



_______________________________________________
ros-users mailing list
ros-users@code.ros.org
https://code.ros.org/mailman/listinfo/ros-users