CGAL users discussion list

[Michel Audette <>]

Hi Laurent, 

I'm seeing the following error, with a number of different choices for mesh size... 

terminate called after throwing an instance of 'CGAL::Assertion_exception'
  what():  CGAL ERROR: assertion violation!
Expr: sq_d > 0
File: /usr/local/include/CGAL/Mesh_3/Protect_edges_sizing_field.h
Line: 416
Aborted

I've been using the following code... See below. So far, I'm trying to get a result with constant tet size, even though the surface mesh size has edges varying between about 10 and 40mm. 

Is this a bug related to the new boundary faithfulness implementation or a consequence of a mismatched size objective? 

Best wishes, 

Michel

#include "vtkCellArray.h"
#include "vtkCellData.h"
#include "vtkInformation.h"
#include "vtkInformationVector.h"
#include "vtkObjectFactory.h"
#include "vtkPointData.h"
#include "vtkUnstructuredGrid.h"
#include "vtkSmartPointer.h"
#include "vtkUnstructuredGridWriter.h"

#ifndef CGAL_USE_VTK
#  define CGAL_USE_VTK
#endif

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>

#include <CGAL/Mesh_triangulation_3.h>
#include <CGAL/Mesh_complex_3_in_triangulation_3.h>
#include <CGAL/Mesh_criteria_3.h>

#include <CGAL/Polyhedral_mesh_domain_with_features_3.h>
#include <CGAL/make_mesh_3.h>

#include <CGAL/IO/Complex_3_in_triangulation_3_to_vtk.h>
//#include <CGAL/refine_mesh_3.h>

// IO
#include <CGAL/IO/Polyhedron_iostream.h>
#include <CGAL/Implicit_mesh_domain_3.h>
#include <CGAL/Mesh_domain_with_polyline_features_3.h>
#include <CGAL/make_mesh_3.h>

// Kernel
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;

// Domain
typedef K::FT FT;
typedef K::Point_3 Point;
typedef FT (Function)(const Point&);

// Polyline
typedef std::vector<Point>        Polyline;
typedef std::list<Polyline>       Polylines;

// Domain 
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Polyhedron_3<K> Polyhedron;
typedef CGAL::Polyhedral_mesh_domain_with_features_3<K> Mesh_domain;
//typedef CGAL::Mesh_domain_with_polyline_features_3<K> Mesh_domain_polylines;

// Triangulation
typedef CGAL::Mesh_triangulation_3< Mesh_domain >::type Tr;
typedef CGAL::Mesh_complex_3_in_triangulation_3<
  Tr,Mesh_domain::Corner_index,Mesh_domain::Curve_segment_index> C3t3;

// Criteria
typedef CGAL::Mesh_criteria_3<Tr> Mesh_criteria;

// To avoid verbose function and named parameters call
using namespace CGAL::parameters;

int main( int argc, char ** argv )
{
  // Verify the number of parameters in the command line
  if( argc < 3)
    {
    std::cerr << "Usage: " << std::endl;
    std::cerr << argv[0] << " inputSurfaceFile.off outputTetFile.vtk " << std::endl;
    return EXIT_FAILURE;
    }

  // Create input polyhedron
  Polyhedron polyhedron;
  std::ifstream input(argv[1]);
  input >> polyhedron;
   
  // Create domain
  Mesh_domain domain(argv[1]);
  
  // Get sharp features
  // Create edge that we want to preserve
  Polylines polylines (1);
  Polyline& polyline = polylines.front();
  
  //std::size_t np = polyhedron.sizeof_points();
  Polyhedron::Point_iterator itr_p;
  int i=0; 
  for(itr_p= polyhedron.points_begin(); itr_p!= polyhedron.points_end(); itr_p++ )
  {
    Point p = (*itr_p);
    polyline.push_back(p);
    std::cout << " pushback points  i " << i++ << "  p " << p << "\n"; 
  }
  polyline.push_back(polyline.front()); // close the line

  // Insert edge in domain
  domain.add_features(polylines.begin(), polylines.end());
  
  // Mesh criteria
  Mesh_criteria criteria(edge_size = 20.0,
                         facet_angle = 10, facet_size = 200, /*facet_distance = 25,*/
                         /*cell_radius_edge_ratio = 3,*/ cell_size = 8000);
  
  // Mesh generation
  C3t3 c3t3 = CGAL::make_mesh_3<C3t3>(domain, criteria);

  vtkSmartPointer<vtkUnstructuredGrid>
    outputUnstructuredGrid = vtkSmartPointer<vtkUnstructuredGrid>::New(); 
  
  CGAL::output_c3t3_to_vtk_unstructured_grid(c3t3, outputUnstructuredGrid);
  outputUnstructuredGrid->Squeeze();

  vtkSmartPointer<vtkUnstructuredGridWriter> writer =
    vtkSmartPointer<vtkUnstructuredGridWriter>::New();

  writer->SetInput(outputUnstructuredGrid);
  writer->SetFileName(argv[2]);
  writer->Write();

  return 0;
}




On Fri, Jun 10, 2011 at 1:16 PM, Michel Audette <> wrote:
> Hi Laurent,
>
> thanks for your prompt and descriptive response. I think that I've
> been lazy about tracking this one down. My apologies.
>
> Best wishes,
>
> Michel
>
>
> On Fri, Jun 10, 2011 at 1:10 PM, Laurent Rineau (GeometryFactory)
> <> wrote:
>> On vendredi 10 juin 2011 18:53:57 Michel Audette wrote:
>>> Dear CGAL developers,
>>>
>
>>
>> Dear Michel,
>>
>> In the documentation of of the class template
>> Polyhedral_mesh_domain_with_features_3 (see [1]), used in the fandisk example,
>> you can see the function
>>
>>  domain.detect_features()
>>
>> But that class template also derives from the class template
>> Mesh_domain_with_polyline_features_3 (see [2]), and that means you can also
>> do:
>>
>>  domain.add_features(polylines.begin(), polylines.end());
>>
>> like it is done in the implicit function example. I think that is what you
>> want. For a polyhedron domain, detect_features() is just a shortcut that
>> computes a set of polylines by detecting sharp edges of the polyhedron, and
>> then passes that set of polylines to add_feature(...).
>>
>> [1] http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Mesh_3_ref/Class_Polyhedral_mesh_domain_with_features_3.html
>> [2] http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Mesh_3_ref/Class_Mesh_domain_with_polyline_features_3.html
>>
>>> PS: I think that the output to vtk is working. I was able to visualize
>>> a result with Paraview.
>>
>> Great!
>>
>> --
>> Laurent Rineau, PhD
>> R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
>> Release Manager of the CGAL Project       http://www.cgal.org/
>>
>> --
>> You are currently subscribed to cgal-discuss.
>> To unsubscribe or access the archives, go to
>> https://lists-sop.inria.fr/wws/info/cgal-discuss
>>
>>
>
>
>
> --
> Michel Audette, Ph.D.
> R & D Engineer,
> Kitware Inc.,
> Chapel Hill, N.C.
>



-- 
Michel Audette, Ph.D.
R & D Engineer,
Kitware Inc.,
Chapel Hill, N.C.