CGAL users discussion list

[Time4Breakfast <>]

Hello,

I am new to CGAL and I am working with 3D data coming from a 3D scanner. The
format is ply and the code to read the vertices and faces in, looks as
follows:

   void operator()( HalfedgeDS& hds )
    { 
      CGAL::Polyhedron_incremental_builder_3<HalfedgeDS> builder( hds,
true);
      builder.begin_surface( _v.size(), _fid.size()/3 );

      // add the vertices
      for( std::vector<VPosition>::const_iterator v = _v.begin();
          v != _v.end(); ++v )
        builder.add_vertex( HalfedgeDS::Vertex::Point( (*v)[0], (*v)[1],
                                                            (*v)[2] ));

      // add the faces
      for( std::vector<unsigned int>::const_iterator fid = _fid.begin();
          fid != _fid.end(); )
      {
        builder.begin_facet();
        for( int i = 0; i < 3; ++i, ++fid )
                builder.add_vertex_to_facet( *fid );
        builder.end_facet();
      }
      builder.end_surface();
    }

The code works fine for all kinds of ply data, yet the data coming from the
scanner contains errors, which the Polyhedron_incremental_builder_3 from
CGAL detects throwing this exception (it occurs while adding the faces):

lookup_halfedge(): input error: facet 11363 shares a halfedge from vertex
42557 to vertex 42523 with facet 8714.
terminate called after throwing an instance of 'CGAL::Assertion_exception'
  what():  CGAL ERROR: assertion violation!
Expr: check_protocoll == 0
File: /usr/include/CGAL/Polyhedron_incremental_builder_3.h
Line: 198

As I cannot alter the data from the scanner, I have to alter the code, that
reads in the data. I thought about something like this:
      // add the faces
      for( std::vector<unsigned int>::const_iterator fid = _fid.begin();
          fid != _fid.end(); )
      {
        builder.begin_facet();
        CGAL::Failure_behaviour set_error_behaviour (
CGAL::Failure_behaviour eb);
        enum Failure_behaviour { CONTINUE };
        for( int i = 0; i < 3; ++i, ++fid )
                builder.add_vertex_to_facet( *fid );
        builder.end_facet();
      }
      builder.end_surface();
    }

But this does not change anything (see preliminaries in the CGAL Manual):
"The CONTINUE value tells the checks to go on after diagnosing the error.
Note that since Cgal 3.4, CONTINUE has the same effect as THROW_EXCEPTION
for errors (but it keeps its meaning for warnings), it is not possible
anymore to let assertion failures simply continue (except by totally
disabling them)." But I don't want to globally disable assertion handling.

So my question is: how can I just ignore erroneous faces?

Best regards and a merry christmas
time4breakfast

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