CGAL users discussion list

[Sebastien Loriot <>]

Sorry for the late reply,

running your code with 5.4 on my linux I got:

Found nearest point of 0 0 0:
index = 0, distance = 0, point: [0 0 0 ]
color = [ 100, 100, 100 ]

as output which seems to be the expected result.

On what platform is the code compiled and run?

Best,

Sebastien.

On 3/6/22 18:46, Yaoyu Hu ( via cgal-discuss 
Mailing List) wrote:
> Hi Sebastien,
>
> In my sample code, I set up a point cloud with 10 points. Their 
> coordinates have a range from [ 0, 0, 0 ] to [0.9, 0.9, 0.9]. Then I try 
> to find the nearest point by using [0, 0, 0] as the query. But I got the 
> result that point index 6 with coordinate [ 0.6, 0.6, 0.6 ] is the 
> nearest one. In fact, no matter what query I use, I always get index 6 
> as the result. I must have done something wrong or misunderstood some 
> details.
>
> Thank you,
>
> Yaoyu
>
> On Fri, Mar 4, 2022 at 4:57 AM Sebastien Loriot < 
> <>> wrote:
>
>     Could you please explain why you think there is a bug, with as
>     assertion
>     for example?
>
>     Thanks,
>
>     Sebastien.
>
>     On 3/3/22 04:06, Yaoyu Hu (
>     <> via cgal-discuss
>     Mailing List) wrote:
>      > I was so dumb that the compiling error in my previous email is
>     due to a
>      > typo.
>      >
>      > I have updated the sample code, now it compiles. Get the updated
>     code here
>      > https://gist.github.com/huyaoyu/6bd9e6b54bc895b7fadebe3863456e92
>     <https://gist.github.com/huyaoyu/6bd9e6b54bc895b7fadebe3863456e92>
>      > <https://gist.github.com/huyaoyu/6bd9e6b54bc895b7fadebe3863456e92
>     <https://gist.github.com/huyaoyu/6bd9e6b54bc895b7fadebe3863456e92>>
>      >
>      > Now I have a new problem. If I run the code, I got the following
>      > outputs. It seems that the search does not work for me. I must
>     have done
>      > something wrong.
>      >
>      > ========== Outputs. ==========
>      >
>      > Hello, test_point_set_nearest_neighbor!
>      > index = 0, point: [ 0 0 0 ], color: [ 100, 100, 100 ]
>      > index = 1, point: [ 0.1 0.1 0.1 ], color: [ 101, 101, 101 ]
>      > index = 2, point: [ 0.2 0.2 0.2 ], color: [ 102, 102, 102 ]
>      > index = 3, point: [ 0.3 0.3 0.3 ], color: [ 103, 103, 103 ]
>      > index = 4, point: [ 0.4 0.4 0.4 ], color: [ 104, 104, 104 ]
>      > index = 5, point: [ 0.5 0.5 0.5 ], color: [ 105, 105, 105 ]
>      > index = 6, point: [ 0.6 0.6 0.6 ], color: [ 106, 106, 106 ]
>      > index = 7, point: [ 0.7 0.7 0.7 ], color: [ 107, 107, 107 ]
>      > index = 8, point: [ 0.8 0.8 0.8 ], color: [ 108, 108, 108 ]
>      > index = 9, point: [ 0.9 0.9 0.9 ], color: [ 109, 109, 109 ]
>      > Found nearest point of 0 0 0:
>      > index = 6, distance = 0, point: [0.6 0.6 0.6 ]
>      > color = [ 106, 106, 106 ]
>      >
>      > ========== Outputs end. ==========
>      >
>      > Any help is appreciated.
>      >
>      > Thank you!
>      >
>      > Yaoyu
>      >
>      > ---------- Forwarded message ---------
>      > From: *Yaoyu Hu* <
>     <> <
>     <>>>
>      > Date: Wed, Mar 2, 2022 at 6:07 PM
>      > Subject: How to do the nearest neighbor search on a Point_set_3 with
>      > properties
>      > To: < <>
>     < <>>>
>      >
>      >
>      > Hi,
>      >
>      > On CGAL v5.4, Ubuntu 20.04, g++ 9.3.0.
>      >
>      > I'm trying to do the nearest neighbor search on a Point_set_3
>     object by
>      > "dD Spatial Searching". The Point_set_3 has a property for point
>     color.
>      > I am trying to follow the example "Using a Point Property Map of a
>      > Polygonal Mesh "
>      >
>     
> https://doc.cgal.org/latest/Spatial_searching/index.html#Spatial_searchingUsingSurfaceMesh
>     
> <https://doc.cgal.org/latest/Spatial_searching/index.html#Spatial_searchingUsingSurfaceMesh>
>
>      >
>     
> <https://doc.cgal.org/latest/Spatial_searching/index.html#Spatial_searchingUsingSurfaceMesh
>     
> <https://doc.cgal.org/latest/Spatial_searching/index.html#Spatial_searchingUsingSurfaceMesh>>
>      >
>      > The reason for referring to the above example is that I suppose
>     points
>      > and colors are saved as property maps in Point_set_3 objects and
>     I need
>      > to get the Index of a point from the Point_set_3 object, such
>     that I can
>      > use the Index object to retrieve a color object saved in the
>     property
>      > map. It looks like the relationship between mesh vertex
>     descriptor and
>      > mesh point property.
>      >
>      > I have two major questions based on my understanding of how
>     Point_set_3
>      > and "dD Spatial Searching " work:
>      >
>      > (1) Do I need an explicit Point_set_3::Index value to be able to
>      > retrieve a property from a property_map of a Point_set_3 object? My
>      > current understanding is yes, I need to have a Point_set_3::Index
>     value
>      > because the property_map is indexed by Point_set_3::Index objects.
>      >
>      > (2) When doing a search by "dD Spatial Searching", if I want to
>     have a
>      > Point_set_3::Index as the search result, I need to use things
>      > like CGAL::Search_traits_adapter such that the search tree will
>     store
>      > Point_set_3::Index for me.
>      >
>      > Based on the above thoughts, I have composed a sample code, which
>      > currently has some compile errors. I also created a GitHub gist
>     if that
>      > is more convenient.
>      > https://gist.github.com/huyaoyu/6bd9e6b54bc895b7fadebe3863456e92
>     <https://gist.github.com/huyaoyu/6bd9e6b54bc895b7fadebe3863456e92>
>      > <https://gist.github.com/huyaoyu/6bd9e6b54bc895b7fadebe3863456e92
>     <https://gist.github.com/huyaoyu/6bd9e6b54bc895b7fadebe3863456e92>>
>      >
>      > The compile error is shown after the code. The error says
>      > that CGAL::Search_traits_adapter needs three template arguments
>     but I
>      > only give it one. I cannot understand why it gives this error since
>      > there are three template arguments already. I failed to proceed any
>      > further and I think it's better to ask for help from experts. I
>     am also
>      > uncertain if my usage of "tree" and "search" is correct in the
>     reset of
>      > the code.
>      >
>      > Can someone help me to resolve the compile error and identify any
>     other
>      > errors regarding "tree" and "search"? Thank you so much!
>      >
>      > ========== Code begins. ==========
>      >
>      > #include <array>
>      > #include <iostream>
>      >
>      > #include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
>      > #include <CGAL/Point_set_3.h>
>      >
>      > #include <CGAL/Orthogonal_k_neighbor_search.h>
>      > #include <CGAL/Search_traits_3.h>
>      > #include <CGAL/Search_traits_adapter.h>
>      >
>      > template < typename CloudT, typename ColorMapT >
>      > typename boost::property_traits<ColorMapT>::value_type nearest_color(
>      >      const CloudT& cloud,
>      >      const ColorMapT& color_map,
>      >      const typename CloudT::Point_3& query) {
>      >
>      >      typedef typename
>     boost::property_traits<ColorMapT>::value_type Color_t;
>      >
>      >      typedef typename CGAL::Kernel_traits<typename
>      > CloudT::Point_3>::Kernel CloudKernel_t;
>      >      typedef CGAL::Search_traits_3<CloudKernel_t>
>     SearchTraits_base_t;
>      >      typedef CGAL::Search_traits_adapter<
>      >          typename CloutT::Index,
>      >          typename CloudT::Point_map,
>      >          SearchTraits_base_t
>      >      > SearchTraits_t;
>      >
>      >      typedef CGAL::Orthogonal_k_neighbor_search<SearchTraits_t>
>      > CloudSearch_t;
>      >      typedef CloudSearch_t::Tree
>      >   CloudSearchTree_t;
>      >      typedef CloudSearchTree_t::Splitter
>      >   CloudSearchSplitter_t;
>      >      typedef CloudSearch_t::Distance
>      >   CloudSearchDistance_t;
>      >
>      >      // Set up a search tree.
>      >      CloudSearchTree_t tree(
>      >          cloud.begin(), cloud.end(),
>      >          CloudSearchSplitter_t(),
>      >          SearchTraits_t( cloud.point_map() ) );
>      >
>      >      // Search.
>      >      CloudSearchDistance_t distance( cloud.point_map() );
>      >      CloudSearch_t search( tree, query, 1, 0, true, distance );
>      >
>      >      const auto& neighbor_point_index = search.begin()->first;
>      >      auto& cloud_neighbor_color = color_map[neighbor_point_index];
>      >
>      >      return cloud_neighbor_color;
>      > }
>      >
>      >
>      > int main(int argc, char** argv) {
>      >      std::cout << "Hello, test_point_set_nearest_neighbor! \n";
>      >
>      >      typedef std::array< unsigned char, 3 > Color_t;
>      >      typedef CGAL::Exact_predicates_inexact_constructions_kernel
>     Kernel_t;
>      >      typedef Kernel_t::Point_3 Point_t;
>      >      typedef CGAL::Point_set_3<Point_t> PointSet_t;
>      >
>      >      PointSet_t cloud;
>      >
>      >      auto [ color_map, flag_added ] =
>      > cloud.add_property_map<Color_t>("color");
>      >
>      >      // Populate the point cloud with color.
>      >      // Omitted.
>      >
>      >      nearest_color( cloud, color_map, Point_t(0, 0, 0) );
>      >
>      >      return 0;
>      > }
>      >
>      > ========== Code ends. ==========
>      >
>      > ========== Compile error begins. ==========
>      >
>      > src/test_point_set_nearest_neighbor.cpp: In function ‘typename
>      > boost::property_traits<IndexMap>::value_type nearest_color(const
>      > CloudT&, const ColorMapT&, const typename CloudT::Point_3&)’:
>      >
>     
> /ws/src/shimizu_test_reconstruct_surface/src/test_point_set_nearest_neighbor.cpp:26:5:
>
>      > error: wrong number of template arguments (1, should be 3)
>      >
>      > (Later error messages are omitted.)
>      >
>      > ========== Compile error ends. ==========
>      >
>      > Thank you!
>      >
>      > Yaoyu
>      >
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