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[omar rodriguez <>]

Well, right now I am only using facets classified as Alpha_shape_3::REGULAR

The following is the code that I am using to change from alpha shape
to polyhedron, maybe I am missing something


----


void operator()(HDS& hds){
                
                std::list<FacetA> facets;
                std::list<FacetA>::iterator facetIterator;
                std::list<Vertex_handleA> vertices;
                QHash<QString, int> addedPoints;
                std::vector<int> toAdd;
                Cell_handleA cellHandler;
                int index;
                
                __as->get_alpha_shape_facets(std::back_inserter(facets),
Alpha_shape_3::REGULAR);
                __as->get_alpha_shape_vertices(std::back_inserter(vertices),
Alpha_shape_3::REGULAR);
                
                std::cout << "Solids " << __as->number_of_solid_components() 
<< "\n";

                CGAL::Polyhedron_incremental_builder_3<HDS> B( hds, true);
                
                B.begin_surface( vertices.size(), facets.size());             
  
                
                int addedVertices = 0;
                
                for (facetIterator = facets.begin(); facetIterator != 
facets.end();
++facetIterator) {


                        cellHandler = facetIterator->first;
                        index = facetIterator->second;
                        
                        // the following ensures that regular facets are 
output
                        // in ccw order
                        
                        
                        if ((__as->classify(*facetIterator) == 
Alpha_shape_3::REGULAR) &&
                                (__as->classify(cellHandler) == 
Alpha_shape_3::INTERIOR)) {
                                cellHandler = cellHandler->neighbor(index);
                                index = 
cellHandler->index(facetIterator->first);
                        }
                        
                        
                        int current;
                        toAdd.clear();
                        
                
                        
                        for (int k = 0; k<3; k++) {
                                current = 
Alpha_shape_3::Triangulation_utils_3::vertex_triple_index(index,
k);
                                
                                QString key = pointToString( 
cellHandler->vertex(current)->point() );
                                
                                // add vertex to polyhedron only once
                                
                                if (addedPoints.contains( key ) ) {
                                        
                                        toAdd.push_back( addedPoints[ key ] );
                                }
                                else {
                                        B.add_vertex( 
cellHandler->vertex(current)->point() );
                                        addedPoints[ key ] = addedVertices;
                                        toAdd.push_back(addedVertices);
                                        addedVertices++;
                                }
                                
                        }
                        
                        
                        if ( B.test_facet( toAdd.begin(), toAdd.end() ) ) {
                                B.begin_facet();
                                for (int i=0; i < 3; i++) {
                                        B.add_vertex_to_facet(toAdd[i]);
                                }
                                B.end_facet();
                        }
                        
                        else {
                                std::cout << " could not add facet \n";
                        }
                        
                        
                }
                
                
                B.end_surface();
                
    }



-----


Omar

+



On Mon, Mar 9, 2009 at 3:04 AM, Benjamin schwarz 
<>
 wrote:
> Hello Omar,
>
>  May the problem be due to the presence of singular facets or
> quasi-manifolds (for instance two 3-simplices connected only by a
> vertex) ?
>
>   Ben
>
> On Sun, Mar 8, 2009 at 6:48 AM, omar rodriguez
> <>
>  wrote:
>> Hello, sorry if this topic has been covered already, I tried searching
>> the archives but they seem to be down at the moment.
>>
>>
>> I am using alpha shapes to get a shape from a set of points, and then
>> I convert it to a polyhedron using
>> CGAL::Polyhedron_incremental_builder_3 to get the boundary facets to
>> perform further operations.
>>
>> This works most of the time, but every so often I get the following error :
>>
>> ---
>> CGAL::Polyhedron_incremental_builder_3<HDS>::
>> add_vertex_to_facet(): input error: disconnected facet complexes at vertex
>> 636:
>>          involved facets are: 472 470 471 (closed cycle) and.
>>
>> terminate called after throwing an instance of 'CGAL::Assertion_exception'
>>  what():  CGAL ERROR: assertion violation!
>> Expr: check_protocoll == 1
>> File: ../../CGAL-3.4/include/CGAL/Polyhedron_incremental_builder_3.h
>> Line: 224
>> ---
>>
>> I have tried using different kernels but the error keeps popping up on
>> the polyhedron builder.
>>
>> Any help would be greatly appreciated.
>>
>> Omar
>>
>> +
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