<snip>
// define a separate point for this specific arm in order to calculate the distance specifically for it.
struct arm_6dof_pos { /*...*/ };
// register the above as 6D cartesian point

namespace boost { namespace geometry {

double comparable_distance(arm_6dof_pos const& p1, arm_6dof_pos const& p2)
{
// calculate the point/point distance (above)
}

template <typename Box>
double comparable_distance(arm_6dof_pos const& p, Box const& b)
{
// calculate the point/box distance
}

}} // namespace

/*...*/

rtree<arm_6dof_pos, ...> tree;
/*fill the rtree*/

arm_6dof_pos query_pos(/*...*/);
tree.query(nearest(query_pos, 1), out);

I hope that I understand your problem correctly and that the above is clear enough.

Thanks for the starter explanation! I'm trying to instantiate things as you described, but I'm running into an issue with NOT_IMPLEMENTED_FOR_THIS_POINT_TYPE. I'm basically mixing the geometry graph example with some of the rtree examples and your description. The rtree is accelerating my graph creation process so I can eventually do a shortest path search on it.

All the important details and the compiler error are in this gist:
https://gist.github.com/ahundt/e790bd17bfc56ae5e5a1

// use boost::array as the type we will adapt
// ...

// I instantiated the torus comparisons:
// perhaps these aren't overload correctly or the boost_array include causes conflicts?
namespace boost { namespace geometry {
double comparable_distance(ArmPos const& p1, ArmPos const& p2 ) ;
template<typename Box>
double comparable_distance(ArmPos const& armpos, Box const& box );
}}

// I define types for the vertex and edge properties (see gist)

// I define all the types necessary to create the rtree and graph

//typedef bg::model::point<double, 3, bg::cs::cartesian> point;
typedef boost::array<double,6> ArmPos;
typedef ArmPos point_type;
typedef bg::model::box<point_type> box;
typedef bg::model::referring_segment<point_type> line_type;
//typedef bg::model::polygon<point, false, false> polygon; // ccw, open polygon

<
boost::vecS, boost::vecS, boost::undirectedS
, bg_vertex_property<point_type> // bundled
, bg_edge_property<line_type>
> graph_type;

typedef boost::graph_traits<graph_type>::vertex_descriptor vertex_type;

// I expected that the point_type of the pair would be seen as implemented
// I also expected that the vertex_type would simply be data not utilized,
// which I believe is true in the case of a simple <point,int> like in the quick start
typedef std::pair<point_type, vertex_type> rtree_value;
typedef boost::geometry::index::rtree<rtree_value,bgi::rstar<16, 4> > knn_rtree_type;

// I instantiate the rtree + graph and get a compiler error
void instantiate_rtree_and_graph(){
// comment these two lines to "fix" compiler error
graph_type graph;
knn_rtree_type rtree;
}

The key line of the error I got, which I didn't expect was:
```/home/ahundt/catkin_ws/build/cs436/assignment3/boost-prefix/include/boost/geometry/core/coordinate_system.hpp:42:5: error: no matching function for call to ‘assertion_failed(mpl_::failed************ (boost::geometry::traits::coordinate_system<boost::array<double, 6ul>, void>::NOT_IMPLEMENTED_FOR_THIS_POINT_TYPE::************)(mpl_::assert_::types<boost::array<double, 6ul>, mpl_::na, mpl_::na, mpl_::na>))’
```
I expected it to work like one of the examples of default value types where the first item is indexed and the second is data such as:
`boost::tuple<geometry::model::point<...>, int, float>`

Any help you might be able to provide with getting the templates to resolve correctly would be appreciated! I also appreciate that you find my use case interesting :-)

Cheers!
Andrew Hundt