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<div class="title">Geometric planning for a rigid body in 3D </div> </div>
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<div class="textblock"><p>This tutorial shows how to plan for a rigid body in 3D. We show how to do this in two ways: <a class="el" href="geometricPlanningSE3.html#geometricSimpleSetup">with</a> and <a class="el" href="geometricPlanningSE3.html#withoutGeometricSimpleSetup">without</a> the <a class="el" href="classompl_1_1geometric_1_1SimpleSetup.html" title="Create the set of classes typically needed to solve a geometric problem.">ompl::geometric::SimpleSetup</a> class. The main difference is that in the latter case <a class="el" href="classompl_1_1base_1_1SpaceInformation.html" title="The base class for space information. This contains all the information about the space planning is d...">ompl::base::SpaceInformation</a> and <a class="el" href="classompl_1_1base_1_1ProblemDefinition.html" title="Definition of a problem to be solved. This includes the start state(s) for the system and a goal spec...">ompl::base::ProblemDefinition</a> need to be explicitly instantiated. Furthermore, the planner to be used must be explicitly instantiated as well. The recommended approach is using <a class="el" href="classompl_1_1geometric_1_1SimpleSetup.html" title="Create the set of classes typically needed to solve a geometric problem.">ompl::geometric::SimpleSetup</a> as this is less bug prone and does not limit the functionality of the code in any way. <br/>
</p>
<dl class="user"><dt><b></b></dt><dd>Setting up geometric planning for a rigid body in 3D requires the following steps:<ul>
<li>identify the space we are planning in: SE(3)</li>
<li>select a corresponding state space from the available ones, or implement one. For SE(3), the <a class="el" href="classompl_1_1base_1_1SE3StateSpace.html" title="A state space representing SE(3)">ompl::base::SE3StateSpace</a> is appropriate.</li>
<li>since SE(3) contains an R<sup>3</sup> component, we need to define bounds.</li>
<li>define the notion of state validity.</li>
<li>define start states and a goal representation.</li>
</ul>
</dd></dl>
<p>Once these steps are complete, the specification of the problem is conceptually done. The set of classes that allow the instantiation of this specification is shown below.</p>
<h2><a class="anchor" id="geometricSimpleSetup"></a>
Using the ompl::geometric::SimpleSetup class</h2>
Assuming the following namespace definitions: <div class="fragment"><pre class="fragment"><span class="keyword">namespace </span>ob = ompl::base;
<span class="keyword">namespace </span>og = ompl::geometric;
</pre></div> And a state validity checking function defined like this: <div class="fragment"><pre class="fragment"><span class="keywordtype">bool</span> isStateValid(<span class="keyword">const</span> <a class="code" href="classompl_1_1base_1_1State.html" title="Definition of an abstract state.">ob::State</a> *state)
</pre></div> We first create an instance of the state space we are planning in. <div class="fragment"><pre class="fragment"><span class="keywordtype">void</span> planWithSimpleSetup(<span class="keywordtype">void</span>)
{
<span class="comment">// construct the state space we are planning in</span>
<a class="code" href="classompl_1_1base_1_1StateSpacePtr.html" title="A boost shared pointer wrapper for ompl::base::StateSpace.">ob::StateSpacePtr</a> space(<span class="keyword">new</span> <a class="code" href="classompl_1_1base_1_1SE3StateSpace.html" title="A state space representing SE(3)">ob::SE3StateSpace</a>());
</pre></div> We then set the bounds for the R<sup>3</sup> component of this state space: <div class="fragment"><pre class="fragment"> <a class="code" href="classompl_1_1base_1_1RealVectorBounds.html" title="The lower and upper bounds for an Rn space.">ob::RealVectorBounds</a> bounds(3);
bounds.setLow(-1);
bounds.setHigh(1);
space->as<<a class="code" href="classompl_1_1base_1_1SE3StateSpace.html" title="A state space representing SE(3)">ob::SE3StateSpace</a>>()->setBounds(bounds);
</pre></div> Create an instance of <a class="el" href="classompl_1_1geometric_1_1SimpleSetup.html" title="Create the set of classes typically needed to solve a geometric problem.">ompl::geometric::SimpleSetup</a>. Instances of <a class="el" href="classompl_1_1base_1_1SpaceInformation.html" title="The base class for space information. This contains all the information about the space planning is d...">ompl::base::SpaceInformation</a>, and <a class="el" href="classompl_1_1base_1_1ProblemDefinition.html" title="Definition of a problem to be solved. This includes the start state(s) for the system and a goal spec...">ompl::base::ProblemDefinition</a> are created internally. <div class="fragment"><pre class="fragment"> <a class="code" href="classompl_1_1geometric_1_1SimpleSetup.html" title="Create the set of classes typically needed to solve a geometric problem.">og::SimpleSetup</a> ss(space);
</pre></div> Set the state validity checker <div class="fragment"><pre class="fragment"> ss.setStateValidityChecker(boost::bind(&isStateValid, _1));
</pre></div> Create a random start state: <div class="fragment"><pre class="fragment"> <a class="code" href="classompl_1_1base_1_1ScopedState.html" title="Definition of a scoped state.">ob::ScopedState<></a> start(space);
start.random();
</pre></div> And a random goal state: <div class="fragment"><pre class="fragment"> <a class="code" href="classompl_1_1base_1_1ScopedState.html" title="Definition of a scoped state.">ob::ScopedState<></a> goal(space);
goal.random();
</pre></div> Set these states as start and goal for SimpleSetup. <div class="fragment"><pre class="fragment"> ss.setStartAndGoalStates(start, goal);
</pre></div> We can now try to solve the problem. This will also trigger a call to <a class="el" href="classompl_1_1geometric_1_1SimpleSetup.html#af7196b38f02c10a5c2fc13261ce29781" title="This method will create the necessary classes for planning. The solve() method will call this functio...">ompl::geometric::SimpleSetup::setup()</a> and create a default instance of a planner, since we have not specified one. Furthermore, <a class="el" href="classompl_1_1base_1_1Planner.html#a948cef726b875317e53ea0f21af40efc" title="Perform extra configuration steps, if needed. This call will also issue a call to ompl::base::SpaceIn...">ompl::base::Planner::setup()</a> is called, which in turn calls <a class="el" href="classompl_1_1base_1_1SpaceInformation.html#ac39aa0c4b92e3ca5acfa75eeb56b080f" title="Perform additional setup tasks (run once, before use). If state validity checking resolution has not ...">ompl::base::SpaceInformation::setup()</a>. This chain of calls will lead to computation of runtime parameters such as the state validity checking resolution. This call returns a boolean flag indicating whether a solution has been found within the specified amount of time (in seconds). <div class="fragment"><pre class="fragment"> <span class="keywordtype">bool</span> solved = ss.solve(1.0);
</pre></div> If a solution has been found, we can optionally simplify it and the display it <div class="fragment"><pre class="fragment"> <span class="keywordflow">if</span> (solved)
{
std::cout << <span class="stringliteral">"Found solution:"</span> << std::endl;
<span class="comment">// print the path to screen</span>
ss.simplifySolution();
ss.getSolutionPath().print(std::cout);
}
</pre></div> <br/>
</p>
<h2><a class="anchor" id="withoutGeometricSimpleSetup"></a>
Without ompl::geometric::SimpleSetup</h2>
Assuming the following namespace definitions: <div class="fragment"><pre class="fragment"><span class="keyword">namespace </span>ob = ompl::base;
<span class="keyword">namespace </span>og = ompl::geometric;
</pre></div> And a state validity checking function defined like this: <div class="fragment"><pre class="fragment"><span class="keywordtype">bool</span> isStateValid(<span class="keyword">const</span> <a class="code" href="classompl_1_1base_1_1State.html" title="Definition of an abstract state.">ob::State</a> *state)
</pre></div> We first create an instance of the state space we are planning in. <div class="fragment"><pre class="fragment"><span class="keywordtype">void</span> plan(<span class="keywordtype">void</span>)
{
<span class="comment">// construct the state space we are planning in</span>
<a class="code" href="classompl_1_1base_1_1StateSpacePtr.html" title="A boost shared pointer wrapper for ompl::base::StateSpace.">ob::StateSpacePtr</a> space(<span class="keyword">new</span> <a class="code" href="classompl_1_1base_1_1SE3StateSpace.html" title="A state space representing SE(3)">ob::SE3StateSpace</a>());
</pre></div> We then set the bounds for the R<sup>3</sup> component of this state space: <div class="fragment"><pre class="fragment"> <a class="code" href="classompl_1_1base_1_1RealVectorBounds.html" title="The lower and upper bounds for an Rn space.">ob::RealVectorBounds</a> bounds(3);
bounds.setLow(-1);
bounds.setHigh(1);
space->as<<a class="code" href="classompl_1_1base_1_1SE3StateSpace.html" title="A state space representing SE(3)">ob::SE3StateSpace</a>>()->setBounds(bounds);
</pre></div> Create an instance of <a class="el" href="classompl_1_1base_1_1SpaceInformation.html" title="The base class for space information. This contains all the information about the space planning is d...">ompl::base::SpaceInformation</a> for the state space <div class="fragment"><pre class="fragment"> <a class="code" href="classompl_1_1base_1_1SpaceInformationPtr.html" title="A boost shared pointer wrapper for ompl::base::SpaceInformation.">ob::SpaceInformationPtr</a> si(<span class="keyword">new</span> <a class="code" href="classompl_1_1base_1_1SpaceInformation.html" title="The base class for space information. This contains all the information about the space planning is d...">ob::SpaceInformation</a>(space));
</pre></div> Set the state validity checker <div class="fragment"><pre class="fragment"> si-><a class="code" href="classompl_1_1base_1_1SpaceInformation.html#a0449ec0893e02aca2bdfc63323b624e5" title="Set the instance of the state validity checker to use. Parallel implementations of planners assume th...">setStateValidityChecker</a>(boost::bind(&isStateValid, _1));
</pre></div> Create a random start state: <div class="fragment"><pre class="fragment"> <a class="code" href="classompl_1_1base_1_1ScopedState.html" title="Definition of a scoped state.">ob::ScopedState<></a> start(space);
start.random();
</pre></div> And a random goal state: <div class="fragment"><pre class="fragment"> <a class="code" href="classompl_1_1base_1_1ScopedState.html" title="Definition of a scoped state.">ob::ScopedState<></a> goal(space);
goal.random();
</pre></div> Create an instance of <a class="el" href="classompl_1_1base_1_1ProblemDefinition.html" title="Definition of a problem to be solved. This includes the start state(s) for the system and a goal spec...">ompl::base::ProblemDefinition</a> <div class="fragment"><pre class="fragment"> <a class="code" href="classompl_1_1base_1_1ProblemDefinitionPtr.html" title="A boost shared pointer wrapper for ompl::base::ProblemDefinition.">ob::ProblemDefinitionPtr</a> pdef(<span class="keyword">new</span> <a class="code" href="classompl_1_1base_1_1ProblemDefinition.html" title="Definition of a problem to be solved. This includes the start state(s) for the system and a goal spec...">ob::ProblemDefinition</a>(si));
</pre></div> Set the start and goal states for the problem definition. <div class="fragment"><pre class="fragment"> pdef->setStartAndGoalStates(start, goal);
</pre></div> Create an instance of a planner <div class="fragment"><pre class="fragment"> <a class="code" href="classompl_1_1base_1_1PlannerPtr.html" title="A boost shared pointer wrapper for ompl::base::Planner.">ob::PlannerPtr</a> planner(<span class="keyword">new</span> <a class="code" href="classompl_1_1geometric_1_1RRTConnect.html" title="RRT-Connect (RRTConnect)">og::RRTConnect</a>(si));
</pre></div> Tell the planner which problem we are interested in solving <div class="fragment"><pre class="fragment"> planner->setProblemDefinition(pdef);
</pre></div> Make sure all the settings for the space and planner are in order. This will also lead to the runtime computation of the state validity checking resolution. <div class="fragment"><pre class="fragment"> planner->setup();
</pre></div> We can now try to solve the problem. This call returns a boolean flag indicating whether a solution has been found within the specified amount of time (in seconds). <div class="fragment"><pre class="fragment"> <span class="keywordtype">bool</span> solved = planner->solve(1.0);
</pre></div> If a solution has been found, we display it. Simplification could be done, but we would need to create an instance of <a class="el" href="classompl_1_1geometric_1_1PathSimplifier.html" title="This class contains routines that attempt to simplify geometric paths.">ompl::geometric::PathSimplifier</a>. <div class="fragment"><pre class="fragment"> <span class="keywordflow">if</span> (solved)
{
<span class="comment">// get the goal representation from the problem definition (not the same as the goal state)</span>
<span class="comment">// and inquire about the found path</span>
<a class="code" href="classompl_1_1base_1_1PathPtr.html" title="A boost shared pointer wrapper for ompl::base::Path.">ob::PathPtr</a> path = pdef->getGoal()->getSolutionPath();
std::cout << <span class="stringliteral">"Found solution:"</span> << std::endl;
<span class="comment">// print the path to screen</span>
path->print(std::cout);
}
</pre></div> <br/>
</p>
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