edge_collapse.h

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  History
    $Log: not supported by cvs2svn $
    Revision 1.16  2006/10/07 15:04:25  cignoni
    removed a useless include

    Revision 1.15  2005/10/12 10:36:26  cignoni
    Removed unused local type Edge. Now it use the standard simplex edge.

    Revision 1.14  2004/12/10 01:04:42  cignoni
    better comments

    Revision 1.13  2004/11/23 10:34:45  cignoni
    passed parameters by reference in many funcs and gcc cleaning


****************************************************************************/

#ifndef __VCG_TETRA_TRI_COLLAPSE
#define __VCG_TETRA_TRI_COLLAPSE


#include<vcg/simplex/face/pos.h>
#include<vcg/simplex/face/topology.h>
#include<vcg/complex/trimesh/allocate.h>

namespace vcg{
namespace tri{  

template <class TRI_MESH_TYPE> 
class EdgeCollapse
{
        public:
  typedef        TRI_MESH_TYPE TriMeshType;
  typedef       typename TriMeshType::FaceType FaceType;
        typedef typename FaceType::VertexType VertexType;
  typedef       typename FaceType::VertexPointer VertexPointer;
  typedef       typename TriMeshType::VertexIterator VertexIterator;
  typedef       typename TriMeshType::FaceIterator FaceIterator;
        typedef typename FaceType::VertexType::CoordType CoordType;
  typedef       typename TriMeshType::VertexType::ScalarType ScalarType;
  typedef typename TriMeshType::FaceContainer FaceContainer;
  typedef typename TriMeshType::VertContainer VertContainer;
        typedef typename TriMeshType::FaceType::EdgeType EdgeType;
        typedef typename std::vector<EdgeType> EdgeVec;
        typedef typename vcg::face::VFIterator<FaceType>  VFI;
        typedef typename std::vector<vcg::face::VFIterator<FaceType> > VFIVec;



        EdgeCollapse()
                {
                };

  ~EdgeCollapse()
                {
                };

        static VFIVec & AV0(){static VFIVec av0; return av0;}
        static VFIVec & AV1(){static VFIVec av1; return av1;}
        static VFIVec & AV01(){static VFIVec av01; return av01;}


        void FindSets(EdgeType &p)
        {
                VertexType * v0 = p.V(0);
                VertexType * v1 = p.V(1);

                AV0().clear();  // Facce incidenti in v0 
                AV1().clear();  // Facce incidenti in v1 
                AV01().clear(); // Facce incidenti in v0 e v1
                
                VFI x;

                for( x.f = v0->VFp(), x.z = v0->VFi(); x.f!=0; ++x)
                {
                        int zv1 = -1;

                        for(int j=0;j<3;++j) 
                                if( x.f->V(j)==&*v1 )   {
                                        zv1 = j;
                                        break;
                                }
                        if(zv1==-1)     AV0().push_back( x ); // la faccia x.f non ha il vertice v1 => e' incidente solo in v0
                        else                            AV01().push_back( x );
                }

                for( x.f = v1->VFp(), x.z = v1->VFi(); x.f!=0; ++x )
                {
                        int zv0 = -1;

                        for(int j=0;j<3;++j)
                                if( x.f->V(j)==&*v0 )   {
                                        zv0 = j;
                                        break;
                                }
                        if(zv0==-1)     AV1().push_back( x ); // la faccia x.f non ha il vertice v1 => e' incidente solo in v0
                }
}
/*
    Link Conditions test, as described in

    Topology Preserving Edge Contraction
    T. Dey, H. Edelsbrunner,
    Pub. Inst. Math. 1999

    Lk (sigma) is the set of all the faces of the cofaces of sigma that are disjoint from sigma

    Lk(v0) inters Lk(v1) == Lk(v0-v1)

    To perform these tests using only the VF adjacency we resort to some virtual counters over
    the vertices and the edges, we implement them as std::maps, and we increase these counters
    by running over all the faces around each vertex of the collapsing edge.

    At the end (after adding dummy stuff) we should have
       2 for vertices not shared
       4 for vertices shared
       2 for edges shared
       1 for edges not shared.


*/
  bool LinkConditions(EdgeType pos)
  {
    typedef typename vcg::face::VFIterator<FaceType> VFIterator;
    // at the end of the loop each vertex must be counted twice
    // except for boundary vertex.
    std::map<VertexPointer,int> VertCnt;
    std::map<std::pair<VertexPointer,VertexPointer>,int> EdgeCnt;

    // the list of the boundary vertexes for the two endpoints
    std::vector<VertexPointer> BoundaryVertexVec[2];

    // Collect vertexes and edges of V0 and V1
    VFIterator vfi;
    for(int i=0;i<2;++i)
    {
      vfi = VFIterator(pos.V(i));
      for( ;!vfi.End();++vfi)
      {
        ++ VertCnt[vfi.V1()];
        ++ VertCnt[vfi.V2()];
        if(vfi.V1()<vfi.V2()) ++EdgeCnt[std::make_pair(vfi.V1(),vfi.V2())];
                         else ++EdgeCnt[std::make_pair(vfi.V2(),vfi.V1())];
      }
      // Now a loop to add dummy stuff: add the dummy vertex and two dummy edges
      // (and remember to increase the counters for the two boundary vertexes involved)
      typename std::map<VertexPointer,int>::iterator vcmit;
      for(vcmit=VertCnt.begin();vcmit!=VertCnt.end();++vcmit)
      {
        if((*vcmit).second==1) // boundary vertexes are counted only once
          BoundaryVertexVec[i].push_back((*vcmit).first);
      }
      if(BoundaryVertexVec[i].size()==2)
      { // aha! one of the two vertex of the collapse is on the boundary
        // so add dummy vertex and two dummy edges
        VertCnt[0]+=2;
        ++ EdgeCnt[std::make_pair(VertexPointer(0),BoundaryVertexVec[i][0]) ] ;
        ++ EdgeCnt[std::make_pair(VertexPointer(0),BoundaryVertexVec[i][1]) ] ;
        // remember to hide the boundaryness of the two boundary vertexes
        ++VertCnt[BoundaryVertexVec[i][0]];
        ++VertCnt[BoundaryVertexVec[i][1]];
      }
    }

    // Final loop to find cardinality of lk( V0-V1 )
    // Note that Lk(edge) is only a set of vertices.
    std::vector<VertexPointer> LkEdge;

    for( vfi = VFIterator(pos.V(0)); !vfi.End(); ++vfi)
    {
      if(vfi.V1() == pos.V(1) ) LkEdge.push_back(pos.V(2));
      if(vfi.V2() == pos.V(1) ) LkEdge.push_back(pos.V(1));
    }

    // if the collapsing edge was a boundary edge, we must add the dummy vertex.
    // Note that this implies that Lk(edge) >=2;
    if(LkEdge.size()==1)
    {
      LkEdge.push_back(0);
    }

    // NOW COUNT!!!
    size_t SharedEdgeCnt=0;
    typename std::map<std::pair<VertexPointer,VertexPointer>, int>::iterator eci;
    for(eci=EdgeCnt.begin();eci!=EdgeCnt.end();++eci)
      if((*eci).second == 2) SharedEdgeCnt ++;

    if(SharedEdgeCnt>0) return false;
    size_t SharedVertCnt=0;
    typename std::map<VertexPointer,int>::iterator vci;
    for(vci=VertCnt.begin();vci!=VertCnt.end();++vci)
      if((*vci).second == 4) SharedVertCnt++;

    if(SharedVertCnt != LkEdge.size() ) return false;

    return true;
  }



  bool LinkConditionsOld(EdgeType  pos){
                
                const int ADJ_1 = TriMeshType::VertexType::NewBitFlag();
                const int ADJ_E = TriMeshType::VertexType::NewBitFlag();
                //enum {ADJ_1= MeshType::VertexType::USER0,
                //          ADJ_E= MeshType::VertexType::USER0<<1} ;
                // const int ALLADJ = ADJ_1|ADJ_E;
                const int NOTALLADJ = ~(ADJ_1 | ADJ_E | TriMeshType::VertexType::VISITED);
                const int NOTALLADJ1 = ~(ADJ_E | TriMeshType::VertexType::VISITED);

                //EdgePosB<MeshType::face_type::face_base> x;
                typename vcg::face::VFIterator<FaceType> x;
                // Clear visited and adj flag for all vertices adj to v0;
                for(x.f = pos.V(0)->VFp(), x.z = pos.V(0)->VFi(); x.f!=0; ++x )         {
                        x.f->V1(x.z)->Flags() &= NOTALLADJ;
                        x.f->V2(x.z)->Flags() &= NOTALLADJ;
                }
                // Clear visited flag for all vertices adj to v1 and set them adj1 to v1;
                for(x.f = pos.V(1)->VFp(), x.z = pos.V(1)->VFi(); x.f!=0; ++x )         {
                        x.f->V1(x.z)->Flags() &= NOTALLADJ1;
                        x.f->V2(x.z)->Flags() &= NOTALLADJ1;
                }
                // Mark vertices adj to v1 as  ADJ_1 and  adj1 to v1;
                for(x.f = pos.V(1)->VFp(), x.z = pos.V(1)->VFi(); x.f!=0; ++x )         {
                        if(x.f->V1(x.z)==pos.V(0)) x.f->V2(x.z)->Flags() |= ADJ_E | ADJ_1;
                        else x.f->V2(x.z)->Flags() |= ADJ_1;
                        if(x.f->V2(x.z)==pos.V(0)) x.f->V1(x.z)->Flags() |= ADJ_E | ADJ_1;
                        else x.f->V1(x.z)->Flags() |= ADJ_1;
                }
                        
                // compute the number of:
                int adj01=0;  // vertices adjacents to both v0 and v1 
                int adje=0;   // vertices adjacents to an egde (usually 2)
                for(x.f = pos.V(0)->VFp(), x.z = pos.V(0)->VFi(); x.f!=0; ++x )         {
                        if(!x.f->V1(x.z)->IsV()) {
                                x.f->V1(x.z)->SetV();
                                if(x.f->V1(x.z)->Flags()&ADJ_1) ++adj01;
                                if(x.f->V1(x.z)->Flags()&ADJ_E) ++adje;
                        }
                        if(!x.f->V2(x.z)->IsV()) {
                                x.f->V2(x.z)->SetV();
                                if(x.f->V2(x.z)->Flags()&ADJ_1) ++adj01;
                                if(x.f->V2(x.z)->Flags()&ADJ_E) ++adje;
                        }
                }

                //bool val=TopoCheck2();
                //if(val != (adj01==adje))              printf("Wrong topo %i %i\n",adj01,adje);
                TriMeshType::VertexType::DeleteBitFlag(ADJ_E);
                TriMeshType::VertexType::DeleteBitFlag(ADJ_1);
                
    return (adj01==adje);
        }



        int DoCollapse(TriMeshType &m, EdgeType & c, const Point3<ScalarType> &p)
        {
                FindSets(c);
                typename VFIVec::iterator i;
                int n_face_del =0 ;
                
                //set Face Face topology
                if (TriMeshType::HasFFTopology())
                {
                        //int e0=c.z;
                        //int e1=c.f->FFi(c.z); //opposite edge

                        //FaceType *f0=c.f;
                        //FaceType *f1=f0->FFp(c.z);
                        //
                        //FaceType *f00=f0->FFp((e0+1)%3);
                        //FaceType *f01=f0->FFp((e0+2)%3);
                        //int If00=f0->FFi((e0+1)%3);
                        //int If01=f0->FFi((e0+2)%3);
                        //
                        //f00->FFp(If00)=f01;
                        //f00->FFi(If00)=If01;
                        //f01->FFp(If01)=f00;
                        //f01->FFi(If01)=If00;


                        //f00=f1->FFp((e1+1)%3);
                        //f01=f1->FFp((e1+2)%3);
                        //If00=f1->FFi((e1+1)%3);
                        //If01=f1->FFi((e1+2)%3);
                        //
                        //f00->FFp(If00)=f01;
                        //f00->FFi(If00)=If01;
                        //f01->FFp(If01)=f00;
                        //f01->FFi(If01)=If00;
                }

                for(i=AV01().begin();i!=AV01().end();++i)
                {       
                        FaceType  & f = *((*i).f);
                        assert(f.V((*i).z) == c.V(0));
                        vcg::face::VFDetach(f,((*i).z+1)%3);
                        vcg::face::VFDetach(f,((*i).z+2)%3);
                        Allocator<TriMeshType>::DeleteFace(m,f);
                        //n_face_del++;
                }

                //set Vertex Face topology
                for(i=AV0().begin();i!=AV0().end();++i)
                {
                        (*i).f->V((*i).z) = c.V(1);                                                                      // In tutte le facce incidenti in v0, si sostituisce v0 con v1
                        (*i).f->VFp((*i).z) = (*i).f->V((*i).z)->VFp(); // e appendo la lista di facce incidenti in v1 a questa faccia
                        (*i).f->VFi((*i).z) = (*i).f->V((*i).z)->VFi();
                        (*i).f->V((*i).z)->VFp() = (*i).f;
                        (*i).f->V((*i).z)->VFi() = (*i).z;
                }
                
                Allocator<TriMeshType>::DeleteVertex(m,*(c.V(0)));
                //c.V(0)->SetD();
                c.V(1)->P()=p;
                return n_face_del;
        }

};

}
}
#endif 

---

vcglib
Author(s): Christian Bersch
autogenerated on Fri Jan 11 09:17:05 2013