CGAL users discussion list

[sergio campo <>]

Ok it works! this is the results(Thank you):

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>

#include <CGAL/Surface_mesh.h>

#include <CGAL/Polygon_mesh_processing/self_intersections.h>

// ----------------------------------------------------------------------------

// CGAL::Polygon_mesh_processing::is_outward_oriented

// ----------------------------------------------------------------------------

#include <CGAL/Polygon_mesh_processing/orientation.h>

// ----------------------------------------------------------------------------

// scan_OFF

// ----------------------------------------------------------------------------

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>

#include <CGAL/Polyhedron_3.h>

// ----------------------------------------------------------------------------

// isOutwardOriented

// ----------------------------------------------------------------------

#include <CGAL/IO/OFF_reader.h>

#include <CGAL/Polygon_mesh_processing/polygon_soup_to_polygon_mesh.h>

#include <fstream>

// ----------------------------------------------------------------------------

// Types

// ----------------------------------------------------------------------------

typedef CGAL::Exact_predicates_inexact_constructions_kernel K;

typedef CGAL::Surface_mesh<K::Point_3>             Mesh;

typedef boost::graph_traits<Mesh>::face_descriptor face_descriptor;

namespace PMP = CGAL::Polygon_mesh_processing;

// polyhedron

typedef CGAL::Polyhedron_3<K> Polyhedron;

bool getMeshFromPolygonSoup(const char* filename, Polyhedron &mesh)

{

std::ifstream input(filename);

if (!input)

{

std::cerr << "Cannot open file " << std::endl;

return false;

}

std::vector<K::Point_3> points;

std::vector< std::vector<std::size_t> > polygons;

if (!CGAL::read_OFF(input, points, polygons))

{

std::cerr << "Error parsing the OFF file " << std::endl;

return false;

}

CGAL::Polygon_mesh_processing::orient_polygon_soup(points, polygons);

CGAL::Polygon_mesh_processing::polygon_soup_to_polygon_mesh(points, polygons, mesh);

return true;

}

bool isOutwardOriented(const char* filename)

{

Polyhedron mesh;

if (!getMeshFromPolygonSoup(filename, mesh))

{

std::cerr << "isOutwardOriented: Cannot open file " << std::endl;

return false;

}

if (CGAL::is_closed(mesh) && (!CGAL::Polygon_mesh_processing::is_outward_oriented(mesh)))

{

std::cerr << "isOutwardOriented: it not outward oriented" << std::endl;

return false;

}

return true;

}

int main(int argc, char* argv[])

{

  const char* filename = argv[1];

  bool is_outward_oriented_mesh = isOutwardOriented(filename);

  if (!is_outward_oriented_mesh)

  {

  std::cerr << "Not a outward oriented mesh" << std::endl;

  }

  

  std::ifstream input(filename);

  if (!input)

  {

  std::cerr << "Cannot open file " << std::endl;

  }

  Polyhedron M;     // a typical definition of a Polyhedron (see other examples)

  scan_OFF(input, M, true);                   // read OFF file in verbose mode

  assert(input);                       // input fails iff mesh is not manifold

    

  return 0;

}

Thanks and Best regards,

Sergio

On Tue, May 29, 2018 at 12:07 PM, Andreas Fabri <> wrote:

Have a look at this example

https://doc.cgal.org/latest/Polygon_mesh_processing/Polygon_mesh_processing_2polygon_soup_example_8cpp-example.html#a3

On 5/29/2018 11:54 AM, sergio campo wrote:

Thanks for your answer. But how It can be detected before corret it?

Sergio

On Tue, May 29, 2018 at 11:03 AM, Andreas Fabri <> wrote:

The orientation of the triangles is not coherent.

You have for examples 2 triangles with an edge going from vertex 0 to vertex 1

You should read a polygon soup and call the function if it can be oriented

andreas

On 5/29/2018 10:56 AM, sergio wrote:

I'm implementing algorithms to detect(Only detection of error, not
correction) if mesh has errors like self-intersection, wrong oriented
normals, etc.
Using scan_OFF with a *.off file it always has result "operator(): input
error: file format is not in OFF."
Why 

// kernel
typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;

// polyhedron
typedef CGAL::Polyhedron_3<Kernel> Polyhedron;

int main(int argc, char* argv[])
{
  const char* filename = (argc > 1) ? argv[1] : "tetrahedron-piramide.off";
  std::ifstream input(filename);
  
  Mesh mesh;
  if (!input || !(input >> mesh) || !CGAL::is_triangle_mesh(mesh))
  {
    std::cerr << "Not a valid input file." << std::endl;
    return 1;
  }
  
  Polyhedron M;     // a typical definition of a Polyhedron (see other
examples)
  scan_OFF(input, M, true);                   // read OFF file in verbose
mode
  assert(input);                       // input fails iff mesh is not
manifold
  return 0;
}

This is a simple mesh and I think it does not have errors. Added file 
tetrahedron-piramide.off
<http://cgal-discuss.949826.n4.nabble.com/file/t375958/tetrahedron-piramide.off> 
.

Thanks in advance



--
Sent from: http://cgal-discuss.949826.n4.nabble.com/

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

phone: +33.492.954.912    skype: andreas.fabri

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

phone: +33.492.954.912    skype: andreas.fabri