CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Could you please provide a minimal example that we could compile, run 
and that would be showing the error?

At first sight, I don't see anything suspicious.

Thanks,

Sebastien.

On 4/17/20 6:25 PM, Juan Jose Casafranca wrote:
> I am trying to find the closest neighbor in a point cloud to a given 
> point. I have followed the documentation example in which the points are 
> stored in a user vector and the Tree only contains indices. Since the 
> results were not what I was expecting, I am also computing the closest 
> neighbor by brute force. Ill explain my code:
>
> I have a vector of points (coarsePoints) and I have a vector of indices 
> (xC_vertices). The indices are the points in coarsePoints that can be 
> marked as closest neighbor.
>
> This is how I compute the closest point using a brute force algorithm
> ```
>
> for (int i = 0; i < d_vertices.size(); ++i) {
>
> Real minDistance = std::numeric_limits<Real>::infinity();
>
> int vertexId = -1;
>
> const auto &dPoint = highResPoints[d_vertices[i]];
>
> const CPF::Point_3 pD{dPoint[0], dPoint[1], dPoint[2]};
>
> for (int j = 0; j < xC_vertices.size(); ++j) {
>
> const auto &xPoint = coarsePoints[xC_vertices[j]];
>
> const CPF::Point_3 pC{xPoint[0], xPoint[1], xPoint[2]};
>
>
> if (CGAL::squared_distance(pC, pD) < minDistance) {
>
> vertexId = j;
>
> minDistance = CGAL::squared_distance(pC, pD);
>
> }
>
> }
>
> ```
>
>
> When using CGAL, I have the following (based on the documentation example):
>
>
> ```
>
> class My_point_property_map
>
> {
>
> const sofa::helper::vector<CPF::SofaTypes::Point> &points;
>
> const std::vector<CPF::SofaTypes::Tetra::value_type> &xC_vertices;
>
> public:
>
> typedef CPF::Point_3 value_type;
>
> typedef value_type &reference;
>
> typedef std::size_t key_type;
>
> typedef boost::lvalue_property_map_tag category;
>
> My_point_property_map(const sofa::helper::vector<CPF::SofaTypes::Point> 
> &pts,
>
> const std::vector<CPF::SofaTypes::Tetra::value_type> &xC_vertices_)
>
> : points(pts)
>
> , xC_vertices(xC_vertices_)
>
> {
>
> }
>
> value_type operator[](key_type k) const
>
> {
>
> const CPF::SofaTypes::Point &sPoint = points[xC_vertices[k]];
>
> return CPF::Point_3{sPoint[0], sPoint[1], sPoint[2]};
>
> }
>
> friend value_type get(const My_point_property_map &ppmap, key_type i) { 
> return ppmap[i]; }
>
> };
>
>
> using SearchTraitsBase = CGAL::Search_traits_3<CPF::K>;
>
> using SearchTraits = CGAL::Search_traits_adapter<std::size_t, 
> My_point_property_map, SearchTraitsBase>;
>
> using NeighborSearch = CGAL::Orthogonal_k_neighbor_search<SearchTraits>;
>
> using Tree = NeighborSearch::Tree;
>
> using Splitter = typename Tree::Splitter;
>
> using SearchDistance = typename NeighborSearch::Distance;
>
>
> int searchNeighbor() {
>
> My_point_property_map ppmap(coarsePoints, xC_vertices);
>
> Tree searchTree(boost::counting_iterator<int>(0),
>
> boost::counting_iterator<int>(xC_vertices.size()),
>
> Splitter(),
>
> SearchTraits(ppmap));
>
> SearchDistance trDistance(ppmap);
>
>
> for (int i = 0; i < d_vertices.size(); ++i) {
>
> NeighborSearch search(searchTree, CPF::Point_3{dPoint[0], dPoint[1], 
> dPoint[2]}, 1, 0, true, trDistance);
>
> for (const auto &searchResult : search) {
>
> if (searchResult.first != vertexId) {
>
> spdlog::get("cpf")->info("Brute force id = {}", vertexId);
>
> spdlog::get("cpf")->info("CGAL id = {}", searchResult.first);
>
> spdlog::get("cpf")->info("Brute force distance = {}", minDistance);
>
> spdlog::get("cpf")->info("CGAL distance = {}", searchResult.second);
>
> }
>
> }
>
> } }
>
> ```
>
>
> This return a los of vertices that are actually different:
>
>
> [2020-04-17 18:10:31.988] [cpf] [info] Brute force id = 386
>
> [2020-04-17 18:10:31.988] [cpf] [info] CGAL id = 84
>
> [2020-04-17 18:10:31.988] [cpf] [info] Brute force distance = 0.0
>
> [2020-04-17 18:10:31.988] [cpf] [info] CGAL distance = 0.041339367896971506
>
>
> I am not sure if I am using incorrectly the NeighborSearch or what is 
> happening. Any ideas what might be wrong?