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[Yaoyu Hu <>]

I sort of figured it out.

I should use CGAL::Point_set_3::point_push_map() and CGAL::Point_set_3::normal_push_map() as described in the documentation. 

Also, although Point_set_3 provides the functions for handling normal vectors, the normal map is not automatically created by default. add_normal_map() should be called before reading the PLY. 

The following code works.

=== Code begins. ===

typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel_t;
typedef Kernel_t::Point_3  Point_t;
typedef Kernel_t::Vector_3 Vector_t;
typedef std::array< unsigned char, 3 > Color_t;

typedef CGAL::Point_set_3<Point_t> PointSet_t;

PointSet_t read_ply_as_point_set( const std::string& fn ) {
    std::ifstream ifs(fn, std::ios::binary);
    if (!ifs) {
        std::stringstream ss;
        ss << "Cannot open " << fn << " for reading. ";
        throw std::runtime_error( ss.str() );
    }

    PointSet_t point_set;

    // Normal map.
    point_set.add_normal_map();

    // Default color.
    const Color_t color_black { { 0, 0, 0 } };

    // The color map.
    PS_ColorMap_t color;
    bool success = false;
    boost::tie( color, success ) =
        point_set.add_property_map<Color_t>("color", color_black);
    assert (success);

    if ( !CGAL::read_PLY_with_properties(
            ifs,
            point_set.index_back_inserter(),
            CGAL::make_ply_point_reader( point_set.point_push_map()  ),
            CGAL::make_ply_normal_reader( point_set.normal_push_map()  ),
            std::make_tuple( color, CGAL::Construct_array(), 
                             CGAL::PLY_property<unsigned char>("red"),
                             CGAL::PLY_property<unsigned char>("green"),
                             CGAL::PLY_property<unsigned char>("blue") ) ) ) {
        ifs.close();
        std::stringstream ss;
        ss << "Read from PLY file " << fn << " failed. ";
        throw std::runtime_error( ss.str() );
    }

    ifs.close();

    return point_set;
}

=== Code ends. ===

Thank you for the help!

Yaoyu

On Thu, Oct 21, 2021 at 3:38 AM Yaoyu Hu <> wrote:

Thank you Andreas for the suggestion. The problem persists after adding the std::ios::binary argument. 

Oh, I forgot to mention that I am on Ubuntu 20.04.

I still have the impression that I might have messed up in using the property maps. 

I tried to debug what is wrong with gdb and I got the following error and a backtrace. I simplify it such that only the filename and line number are preserved. And also, I tried to list the relevant lines at some backtrace points.

=== Debug info. ===

terminate called after throwing an instance of 'CGAL::Assertion_exception'
  what():  CGAL ERROR: assertion violation!
Expr: _idx < data_.size()
File: /home/yaoyu/Libraries/CGAL/cgal/Surface_mesh/include/CGAL/Surface_mesh/Properties.h
Line: 193

#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#1  0x00007ffff7642859 in __GI_abort () at abort.c:79
#2  0x00007ffff7a17911 in ?? () from /lib/x86_64-linux-gnu/libstdc++.so.6
#3  0x00007ffff7a2338c in ?? () from /lib/x86_64-linux-gnu/libstdc++.so.6
#4  0x00007ffff7a233f7 in std::terminate() () from /lib/x86_64-linux-gnu/libstdc++.so.6
#5  0x00007ffff7a236a9 in __cxa_throw () from /lib/x86_64-linux-gnu/libstdc++.so.6
#6  /home/yaoyu/Libraries/CGAL/cgal/STL_Extension/include/CGAL/assertions_impl.h:170
#7  /home/yaoyu/Libraries/CGAL/cgal/Surface_mesh/include/CGAL/Surface_mesh/Properties.h:193

190    /// Access the i'th element. No range check is performed!
191    reference operator[](std::size_t _idx)
192    {
193        CGAL_assertion( _idx < data_.size() );
194        return data_[_idx];
195    }

#8  /home/yaoyu/Libraries/CGAL/cgal/Surface_mesh/include/CGAL/Surface_mesh/Properties.h:587

583    /// Access the property associated with the key \c i.
584    reference operator[](const I& i) const
585    {
586      CGAL_assertion(parray_ != nullptr);
587      return (*parray_)[i];
588    }
589
590    iterator begin() { return parray_->begin(); }
591    iterator end() { return parray_->end(); }

#9  /usr/include/boost/property_map/property_map.hpp:311

307  template <class PropertyMap, class Reference, class K, class V>
308  inline void
309  put(const put_get_helper<Reference, PropertyMap>& pa, K k, const V& v)
310  {
311    static_cast<const PropertyMap&>(pa)[k] = v;
312  }
313
314  //=========================================================================
315  // Adapter to turn a RandomAccessIterator into a property map

#10 /home/yaoyu/Libraries/CGAL/cgal/Stream_support/include/CGAL/IO/PLY/PLY_reader.h:670

665  typedef typename boost::property_traits<PropertyMap>::value_type PmapValueType;
666
667  std::tuple<T...> values;
668  Filler<sizeof...(T)-1>::fill(element, values, current);
669  PmapValueType new_value = call_functor<PmapValueType>(std::get<1>(current), values);
670  put(std::get<0>(current), new_element, new_value);
671
672  process_properties(element, new_element, std::forward<NextPropertyBinder>(next),
673                     std::forward<PropertyMapBinders>(properties)...);

#11 /home/yaoyu/Libraries/CGAL/cgal/Point_set_processing_3/include/CGAL/IO/read_ply_points.h:177

172      }
173
174      if(element.name() == "vertex" || element.name() == "vertices")
175      {
176        OutputValueType new_element;
177        IO::internal::process_properties(element, new_element, std::forward<PropertyHandler>(properties)...);
178        *(output ++) = new_element;
179      }
180    }
181  }

#12 /home/yaoyu/Libraries/CGAL/cgal/Point_set_processing_3/include/CGAL/IO/read_ply_points.h:196

191                              OutputIterator output,
192                              PropertyHandler&& ... properties)
193 {
194  typedef typename value_type_traits<OutputIterator>::type OutputValueType;
195
196  return read_PLY_with_properties<OutputValueType>(is, output, std::forward<PropertyHandler>(properties)...);
197 }
198
199 /// \endcond

=== End of debug info. ===

Thank you!

On Thu, Oct 21, 2021 at 2:10 AM Andreas Fabri <> wrote:

Hello,

At least on Windows if you read a binary ply file you must open the stream in binary mode.

Can you try    std::ifstream ifs(fn, std::ios::binary);

Best,

Andreas

On 10/21/2021 1:20 AM, Yaoyu Hu ( via cgal-discuss Mailing List) wrote:

Hi,

I am trying to read a binary PLY file as CGAL::Point_set_3 but I can't get it right.

I am using CGAL 5.3.

I suppose there is not a dedicated example showing how to read a PLY file as Point_set_3 that has properties. For my PLY file, there are point normal and color stored. The code I tried to read it as CGAL::Point_set_3 is as follows:

=== Code begins. ===

typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel_t;
typedef Kernel_t::Point_3  Point_t;
typedef Kernel_t::Vector_3 Vector_t;
typedef std::array< unsigned char, 3 > Color_t;

typedef CGAL::Point_set_3<Point_t> PointSet_t;

typedef PointSet_t::Point_map PS_PointMap_t;
typedef PointSet_t::Vector_map PS_NormalMap_t;
typedef PointSet_t::Property_map<Color_t> PS_ColorMap_t;

PointSet_t sr::read_ply_as_point_set( const std::string& fn ) {
    std::ifstream ifs(fn);

    PointSet_t point_set;

    // Default color.
    const Color_t color_black { { 0, 0, 0 } };

    // The color map.
    PS_ColorMap_t color;
    bool success = false;
    boost::tie( color, success ) =
        point_set.add_property_map<Color_t>("color", color_black);
    assert (success);

    // Read PLY.
    CGAL::read_PLY_with_properties(
            ifs,
            point_set.index_back_inserter(),
            CGAL::make_ply_point_reader( PS_PointMap_t() ),
            CGAL::make_ply_normal_reader( PS_NormalMap_t() ),
            std::make_tuple( PS_ColorMap_t(), CGAL::Construct_array(), 
                             CGAL::PLY_property<unsigned char>("red"),
                             CGAL::PLY_property<unsigned char>("green"),
                             CGAL::PLY_property<unsigned char>("blue") ) ) )

    return point_set;
}

=== Code ends. ===

The codes that I am not sure about are the lines of CGAL::make_ply_point_reader() and CGAL::make_ply_normal_reader(), they are probably wrong but I don't know how to get it right.

Thanks!

Yaoyu

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-- 
Andreas Fabri, PhD
Chief Officer, GeometryFactory
Editor, The CGAL Project

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