Re: [ompl-users] Straight line (in config space) path?

[Patrick B. <bee...@gm...>]

I completely understand you Lydia.  I also started a thread for MoveIt!
that it might be useful to add this kind of check as an pre-planning
Adapter, that lies outside OMPL.  The funny thing is that some of the
MoveIt! maintainers say the exact opposite: "This is something you should
do in your planner".  So I'm searching for the best solution.

I like Mark's idea, though. I can see potentially using Mark's solution
even for the related issue I brought up earlier about the PRM-derivatives
always using the full amount of time to plan.  As I had remarked earlier,
it would be nice for those to have a "switch" from exploration to straight
exploitation of the roadmap, providing the first solution found in the
roadmap without expanding it more.  Instead of mucking up PRM and its
derivatives to support this, it might be best to write alternative planners
that do this and simply run the two side-by-side, where one continues to
grow the roadmap in the background and the other uses a static roadmap.
Though doing this may involve copying roadmaps, which I've seen get pretty
large in my playing around with the latest LazyPRM* that allows roadmap
loading.

Thanks for the help folks!

On Wed, Jun 24, 2020 at 11:52 AM Lydia Kavraki <ka...@ri...> wrote:

> Thanks Mark. I would not recommend that all planners are changed for this.
> This is something to check before running a planner.
>
> LK
>
> On Jun 24, 2020, at 10:54 AM, Mark Moll <mm...@ri...> wrote:
>
> You can (sort of) do this in OMPL without having to modify each planner,
> although it’s a little convoluted:
> 1. Create an instance of AnytimePathShortening (APS)
> 2. Add an instance of your preferred planner to APS
> 3. Create a new “planner” that only tries straight line interpolation and
> add an instance to APS
> 4. Set the termination condition to be
> exactSolnPlannerTerminationCondition
> <http://ompl.kavrakilab.org/namespaceompl_1_1base.html#a71261936b94c44c59a9f26168b30ea1f>(…)
> (to make sure APS stops when the first solution is found.
>
> Best,
>
> Mark
>
>
>
> On Jun 23, 2020, at 8:01 AM, Patrick Beeson <bee...@gm...> wrote:
>
> In using OMPL via MoveIt!, I'm noticing that OMPL often does a whole lot
> of work to plan even when there's a straight line in configuration space
> from the start to the goal.  So it'll find a solution of let's say 6-10
> points then that gets shortened down to 2, the start and goal.
>
> In asking about just checking the 2 point plan of start/goal for
> collisions in MoveIt! (
> https://answers.ros.org/question/355617/can-moveit-first-check-shortest-path-before-planning/),
> the short answer was "your planner needs to support it".  So, now I'm
> asking here, does OMPL support this functionality as an option prior to
> running plans, and is this exposed via the MoveIt! API into OMPL?  If so,
> I'm missing where this is documented.  If not, is there a viable solution
> to do this in OMPL?
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