Frequently Asked Questions

• Q: Why is the code I added to the OMPL source not being compiled?

  See the OMPL Build System. Essentially, just run cmake again after adding new files.

• Q: How do I specify collision checking for a planner?

  A: See page on state validation.

• Q: Can I visualize the exploration data structure used by a planner?

  A: Yes. You need to call ompl::base::Planner::getPlannerData(). This will give you an instance of ompl::base::PlannerData which contains all the states and the edges between them. The PlannerData can be exported in GraphML format which can be read by a number of external programs such a graph-tool and Gephi.

• Q: Can I change the state space during planning?

  A: No. Such changes will make the code crash.

• Q: Can I set the sampler to use for a planner?

  A: Yes. The sampler instances used by planners are allocated by either ompl::base::SpaceInformation::allocStateSampler() (which calls ompl::base::StateSpace::allocStateSampler() under the hood) or by ompl::base::SpaceInformation::allocValidStateSampler(). By default, ompl::base::SpaceInformation::allocValidStateSampler() produces an instance of ompl::base::UniformValidStateSampler, unless a sampler allocator was specified. The simplest way to change which sampler is allocated is to specify a sampler allocator. Calling ompl::base::SpaceInformation::setValidStateSamplerAllocator() allows the user to do just that:

  #include "ompl/base/samplers/ObstacleBasedValidStateSampler.h"
  ...
  ompl::base::ValidStateSamplerPtr allocValidStateSampler(const ompl::base::SpaceInformation *si)
  {
      return ompl::base::ValidStateSamplerPtr(new ompl::base::ObstacleBasedValidStateSampler(si));
  }
  ...
  ompl::base::StateSpacePtr space(...);
  ompl::base::SpaceInformationPtr si(new ompl::base::SpaceInformation(space));
  si->setValidStateSamplerAllocator(std::bind(&allocValidStateSampler, std::placeholders::_1));
  // for simplified calls, you can also use:
  // si->setValidStateSamplerAllocator(&allocValidStateSampler);

  The example above is similarly applicable for ompl::base::StateSamplerAllocator ompl::control::ControlSamplerAllocator, ompl::control::DirectedControlSamplerAllocator and ompl::base::PlannerAllocator.

If your question is still not answered, another good place to check is the mailing list archive.