// Copyright (C) 2007-2012  CEA/DEN, EDF R&D, OPEN CASCADE
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
//
// See http://www.salome-platform.org/ or email : webmaster.salome@opencascade.com
//

// File      : NETGENPlugin_NETGEN_2D_ONLY.cxx
// Author    : Edward AGAPOV (OCC)
// Project   : SALOME
//
#include "NETGENPlugin_NETGEN_2D_ONLY.hxx"

#include "NETGENPlugin_Mesher.hxx"
#include "NETGENPlugin_Hypothesis_2D.hxx"

#include "SMDS_MeshElement.hxx"
#include "SMDS_MeshNode.hxx"
#include "SMESHDS_Mesh.hxx"
#include "SMESH_Comment.hxx"
#include "SMESH_Gen.hxx"
#include "SMESH_Mesh.hxx"
#include "SMESH_MesherHelper.hxx"
#include "StdMeshers_FaceSide.hxx"
#include "StdMeshers_MaxElementArea.hxx"
#include "StdMeshers_LengthFromEdges.hxx"
#include "StdMeshers_QuadranglePreference.hxx"

#include <Precision.hxx>
#include <Standard_ErrorHandler.hxx>
#include <Standard_Failure.hxx>

#include "utilities.h"

#include <list>
#include <vector>
#include <limits>

/*
  Netgen include files
*/
namespace nglib {
#include <nglib.h>
}
#ifndef OCCGEOMETRY
#define OCCGEOMETRY
#endif
#include <occgeom.hpp>
#include <meshing.hpp>
//#include <meshtype.hpp>
namespace netgen {
  extern int OCCGenerateMesh (OCCGeometry&, Mesh*&, int, int, char*);
  extern MeshingParameters mparam;
}

using namespace std;
using namespace netgen;
using namespace nglib;

//#define DUMP_SEGMENTS

//=============================================================================
/*!
 *  
 */
//=============================================================================

NETGENPlugin_NETGEN_2D_ONLY::NETGENPlugin_NETGEN_2D_ONLY(int hypId, int studyId,
                                                         SMESH_Gen* gen)
  : SMESH_2D_Algo(hypId, studyId, gen)
{
  MESSAGE("NETGENPlugin_NETGEN_2D_ONLY::NETGENPlugin_NETGEN_2D_ONLY");
  _name = "NETGEN_2D_ONLY";
  
  _shapeType = (1 << TopAbs_FACE);// 1 bit /shape type

  _compatibleHypothesis.push_back("MaxElementArea");
  _compatibleHypothesis.push_back("LengthFromEdges");
  _compatibleHypothesis.push_back("QuadranglePreference");
  _compatibleHypothesis.push_back("NETGEN_Parameters_2D");

  _hypMaxElementArea = 0;
  _hypLengthFromEdges = 0;
  _hypQuadranglePreference = 0;
  _hypParameters = 0;
}

//=============================================================================
/*!
 *  
 */
//=============================================================================

NETGENPlugin_NETGEN_2D_ONLY::~NETGENPlugin_NETGEN_2D_ONLY()
{
  MESSAGE("NETGENPlugin_NETGEN_2D_ONLY::~NETGENPlugin_NETGEN_2D_ONLY");
}

//=============================================================================
/*!
 *  
 */
//=============================================================================

bool NETGENPlugin_NETGEN_2D_ONLY::CheckHypothesis (SMESH_Mesh&         aMesh,
                                                   const TopoDS_Shape& aShape,
                                                   Hypothesis_Status&  aStatus)
{
  _hypMaxElementArea = 0;
  _hypLengthFromEdges = 0;
  _hypQuadranglePreference = 0;

  const list<const SMESHDS_Hypothesis*>& hyps = GetUsedHypothesis(aMesh, aShape, false);

  if (hyps.empty())
  {
    aStatus = HYP_OK; //SMESH_Hypothesis::HYP_MISSING;
    return true;  // (PAL13464) can work with no hypothesis, LengthFromEdges is default one
  }

  aStatus = HYP_MISSING;

  list<const SMESHDS_Hypothesis*>::const_iterator ith;
  for (ith = hyps.begin(); ith != hyps.end(); ++ith )
  {
    const SMESHDS_Hypothesis* hyp = (*ith);

    string hypName = hyp->GetName();

    if      ( hypName == "MaxElementArea")
      _hypMaxElementArea = static_cast<const StdMeshers_MaxElementArea*> (hyp);
    else if ( hypName == "LengthFromEdges" )
      _hypLengthFromEdges = static_cast<const StdMeshers_LengthFromEdges*> (hyp);
    else if ( hypName == "QuadranglePreference" )
      _hypQuadranglePreference = static_cast<const StdMeshers_QuadranglePreference*>(hyp);
    else if ( hypName == "NETGEN_Parameters_2D" )
      _hypParameters = static_cast<const NETGENPlugin_Hypothesis_2D*>(hyp);
    else {
      aStatus = HYP_INCOMPATIBLE;
      return false;
    }
  }

  int nbHyps = bool(_hypMaxElementArea) + bool(_hypLengthFromEdges) + bool(_hypParameters );
  if ( nbHyps > 1 )
    aStatus = HYP_CONCURENT;
  else if ( nbHyps == 1)
    aStatus = HYP_OK;

  return ( aStatus == HYP_OK );
}

//================================================================================
/*!
 * \brief Fill netgen mesh with segments
  * \retval SMESH_ComputeErrorPtr - error description
 */
//================================================================================

static TError addSegmentsToMesh(netgen::Mesh&                    ngMesh,
                                OCCGeometry&                     geom,
                                const TSideVector&               wires,
                                SMESH_MesherHelper&              helper,
                                vector< const SMDS_MeshNode* > & nodeVec)
{
  // ----------------------------
  // Check wires and count nodes
  // ----------------------------
  int nbNodes = 0;
  double totalLength = 0;
  for ( int iW = 0; iW < wires.size(); ++iW )
  {
    StdMeshers_FaceSidePtr wire = wires[ iW ];
    if ( wire->MissVertexNode() )
    {
      // Commented for issue 0020960. It worked for the case, let's wait for case where it doesn't.
      // It seems that there is no reason for this limitation
//       return TError
//         (new SMESH_ComputeError(COMPERR_BAD_INPUT_MESH, "Missing nodes on vertices"));
      if (getenv("USER") && string("eap")==getenv("USER"))
        cout << "Warning: NETGENPlugin_NETGEN_2D_ONLY : try to work with missing nodes on vertices"<<endl;
    }
    const vector<UVPtStruct>& uvPtVec = wire->GetUVPtStruct();
    if ( uvPtVec.size() != wire->NbPoints() )
      return TError
        (new SMESH_ComputeError(COMPERR_BAD_INPUT_MESH,
                                SMESH_Comment("Unexpected nb of points on wire ") << iW
                                << ": " << uvPtVec.size()<<" != "<<wire->NbPoints()));
    nbNodes += wire->NbPoints();
    totalLength += wire->Length();
  }
  nodeVec.reserve( nbNodes );

  // -----------------
  // Fill netgen mesh
  // -----------------

//   netgen::Box<3> bb = geom.GetBoundingBox();
//   bb.Increase (bb.Diam()/10);
//   ngMesh.SetLocalH (bb.PMin(), bb.PMax(), 0.5); // set grading

  // map for nodes on vertices since they can be shared between wires
  // ( issue 0020676, face_int_box.brep)
  map<const SMDS_MeshNode*, int > node2ngID;

  const int faceID = 1, solidID = 0;
  if ( ngMesh.GetNFD() < 1 )
    ngMesh.AddFaceDescriptor (FaceDescriptor(faceID, solidID, solidID, 0));

  for ( int iW = 0; iW < wires.size(); ++iW )
  {
    StdMeshers_FaceSidePtr wire = wires[ iW ];
    const vector<UVPtStruct>& uvPtVec = wire->GetUVPtStruct();
    const int nbSegments = wire->NbPoints() - 1;

    // compute length of every segment
    vector<double> segLen( nbSegments );
    for ( int i = 0; i < nbSegments; ++i )
      segLen[i] = SMESH_TNodeXYZ( uvPtVec[ i ].node ).Distance( uvPtVec[ i+1 ].node );

    int edgeID = 1, posID = -2;
    bool isInternalWire = false;
    for ( int i = 0; i < nbSegments; ++i ) // loop on segments
    {
      // Add the first point of a segment
      const SMDS_MeshNode * n = uvPtVec[ i ].node;
      const int posShapeID = n->getshapeId();
      bool onVertex = ( n->GetPosition()->GetTypeOfPosition() == SMDS_TOP_VERTEX );

      // skip nodes on degenerated edges
      if ( helper.IsDegenShape( posShapeID ) &&
           helper.IsDegenShape( uvPtVec[ i+1 ].node->getshapeId() ))
        continue;

      int ngID1 = ngMesh.GetNP() + 1, ngID2 = ngID1+1;
      if ( onVertex )
        ngID1 = node2ngID.insert( make_pair( n, ngID1 )).first->second;
      if ( ngID1 > ngMesh.GetNP() )
      {
        MeshPoint mp( Point<3> (n->X(), n->Y(), n->Z()) );
        ngMesh.AddPoint ( mp, 1, EDGEPOINT );
        nodeVec.push_back( n );
      }
      else
      {
        ngID2 = ngMesh.GetNP() + 1;
        if ( i > 0 ) // prev segment belongs to same wire
        {
          Segment& prevSeg = ngMesh.LineSegment( ngMesh.GetNSeg() );
          prevSeg[1] = ngID1;
        }
      }

      // Add the segment
      Segment seg;

      seg[0] = ngID1;  // ng node id
      seg[1] = ngID2;  // ng node id

      seg.edgenr = ngMesh.GetNSeg() + 1;// segment id
      seg.si = faceID;                  // = geom.fmap.FindIndex (face);

      for ( int iEnd = 0; iEnd < 2; ++iEnd)
      {
        const UVPtStruct& pnt = uvPtVec[ i + iEnd ];

        seg.epgeominfo[ iEnd ].dist = pnt.param; // param on curve
        seg.epgeominfo[ iEnd ].u    = pnt.u;
        seg.epgeominfo[ iEnd ].v    = pnt.v;

        // find out edge id and node parameter on edge
        onVertex = ( pnt.node->GetPosition()->GetTypeOfPosition() == SMDS_TOP_VERTEX );
        if ( onVertex || posShapeID != posID )
        {
          // get edge id
          double normParam = pnt.normParam;
          if ( onVertex )
            normParam = 0.5 * ( uvPtVec[ i ].normParam + uvPtVec[ i+1 ].normParam );
          const TopoDS_Edge& edge = wire->Edge( wire->EdgeIndex( normParam ));
          edgeID = geom.emap.FindIndex( edge );
          posID  = posShapeID;
          isInternalWire = ( edge.Orientation() == TopAbs_INTERNAL );
          // if ( onVertex ) // param on curve is different on each of two edges
          //   seg.epgeominfo[ iEnd ].dist = helper.GetNodeU( edge, pnt.node );
        }
        seg.epgeominfo[ iEnd ].edgenr = edgeID; //  = geom.emap.FindIndex(edge);
      }

      ngMesh.AddSegment (seg);
      {
        // restrict size of elements near the segment
        SMESH_TNodeXYZ np1( n ), np2( uvPtVec[ i+1 ].node );
        // get an average size of adjacent segments to avoid sharp change of
        // element size (regression on issue 0020452, note 0010898)
        int iPrev = SMESH_MesherHelper::WrapIndex( i-1, nbSegments );
        int iNext = SMESH_MesherHelper::WrapIndex( i+1, nbSegments );
        double avgH = ( segLen[ iPrev ] + segLen[ i ] + segLen[ iNext ]) / 3;

        NETGENPlugin_Mesher::RestrictLocalSize( ngMesh, 0.5*(np1+np2), avgH );
      }
#ifdef DUMP_SEGMENTS
        cout << "Segment: " << seg.edgenr << endl
           << "\tp1: " << seg[0] << endl
           << "\tp2: " << seg[1] << endl
           << "\tp0 param: " << seg.epgeominfo[ 0 ].dist << endl
           << "\tp0 uv: " << seg.epgeominfo[ 0 ].u <<", "<< seg.epgeominfo[ 0 ].v << endl
           << "\tp0 edge: " << seg.epgeominfo[ 0 ].edgenr << endl
           << "\tp1 param: " << seg.epgeominfo[ 1 ].dist << endl
           << "\tp1 uv: " << seg.epgeominfo[ 1 ].u <<", "<< seg.epgeominfo[ 1 ].v << endl
           << "\tp1 edge: " << seg.epgeominfo[ 1 ].edgenr << endl;
#endif
      if ( isInternalWire )
      {
        swap (seg[0], seg[1]);
        swap( seg.epgeominfo[0], seg.epgeominfo[1] );
        seg.edgenr = ngMesh.GetNSeg() + 1; // segment id
        ngMesh.AddSegment (seg);
#ifdef DUMP_SEGMENTS
        cout << "Segment: " << seg.edgenr << endl << "\tis REVRESE of the previous one" << endl;
#endif
      }
    } // loop on segments on a wire

    // close chain of segments
    if ( nbSegments > 0 )
    {
      Segment& lastSeg = ngMesh.LineSegment( ngMesh.GetNSeg() - int( isInternalWire));
      const SMDS_MeshNode * lastNode = uvPtVec.back().node;
      lastSeg[1] = node2ngID.insert( make_pair( lastNode, lastSeg[1] )).first->second;
      if ( lastSeg[1] > ngMesh.GetNP() )
      {
        MeshPoint mp( Point<3> (lastNode->X(), lastNode->Y(), lastNode->Z()) );
        ngMesh.AddPoint ( mp, 1, EDGEPOINT );
        nodeVec.push_back( lastNode );
      }
      if ( isInternalWire )
      {
        Segment& realLastSeg = ngMesh.LineSegment( ngMesh.GetNSeg() );
        realLastSeg[0] = lastSeg[1];
      }
    }

  } // loop on wires of a face

  // add a segment instead of internal vertex
  NETGENPlugin_Internals intShapes( *helper.GetMesh(), helper.GetSubShape(), /*is3D=*/false );
  NETGENPlugin_Mesher::addIntVerticesInFaces( geom, ngMesh, nodeVec, intShapes );

  ngMesh.CalcSurfacesOfNode();

  return TError();
}

//=============================================================================
/*!
 *Here we are going to use the NETGEN mesher
 */
//=============================================================================

bool NETGENPlugin_NETGEN_2D_ONLY::Compute(SMESH_Mesh&         aMesh,
                                          const TopoDS_Shape& aShape)
{
#ifdef WITH_SMESH_CANCEL_COMPUTE
  netgen::multithread.terminate = 0;
#endif
  MESSAGE("NETGENPlugin_NETGEN_2D_ONLY::Compute()");

  SMESHDS_Mesh* meshDS = aMesh.GetMeshDS();
  int faceID = meshDS->ShapeToIndex( aShape );

  SMESH_MesherHelper helper(aMesh);
  _quadraticMesh = helper.IsQuadraticSubMesh(aShape);
  helper.SetElementsOnShape( true );
  const bool ignoreMediumNodes = _quadraticMesh;
  
  // ------------------------
  // get all edges of a face
  // ------------------------
  const TopoDS_Face F = TopoDS::Face( aShape.Oriented( TopAbs_FORWARD ));
  TError problem;
  TSideVector wires = StdMeshers_FaceSide::GetFaceWires( F, aMesh, ignoreMediumNodes, problem );
  if ( problem && !problem->IsOK() )
    return error( problem );
  int nbWires = wires.size();
  if ( nbWires == 0 )
    return error( "Problem in StdMeshers_FaceSide::GetFaceWires()");
  if ( wires[0]->NbSegments() < 3 ) // ex: a circle with 2 segments
    return error(COMPERR_BAD_INPUT_MESH,
                 SMESH_Comment("Too few segments: ")<<wires[0]->NbSegments());

  // --------------------
  // compute edge length
  // --------------------

  NETGENPlugin_Mesher aMesher( &aMesh, aShape, /*isVolume=*/false);
  netgen::OCCGeometry occgeo;
  aMesher.PrepareOCCgeometry( occgeo, F, aMesh );
  occgeo.fmap.Clear(); // face can be reversed, which is wrong in this case (issue 19978)
  occgeo.fmap.Add( F );

  if ( _hypParameters )
  {
    aMesher.SetParameters(_hypParameters);
  }
  else
  {
    double edgeLength = 0;
    if (_hypLengthFromEdges || (!_hypLengthFromEdges && !_hypMaxElementArea))
    {
      int nbSegments = 0;
      for ( int iW = 0; iW < nbWires; ++iW )
      {
        edgeLength += wires[ iW ]->Length();
        nbSegments += wires[ iW ]->NbSegments();
      }
      if ( nbSegments )
        edgeLength /= nbSegments;
    }
    if ( _hypMaxElementArea )
    {
      double maxArea = _hypMaxElementArea->GetMaxArea();
      edgeLength = sqrt(2. * maxArea/sqrt(3.0));
    }
    if ( edgeLength < DBL_MIN )
      edgeLength = occgeo.GetBoundingBox().Diam();

    netgen::mparam.maxh = edgeLength;
    netgen::mparam.minh = aMesher.GetDefaultMinSize( aShape, netgen::mparam.maxh );
    netgen::mparam.quad = _hypQuadranglePreference ? 1 : 0;
    netgen::mparam.grading = 0.7; // very coarse mesh by default
  }
#ifdef NETGEN_NEW
  occgeo.face_maxh = netgen::mparam.maxh;
#endif

  // -------------------------
  // Make input netgen mesh
  // -------------------------

  NETGENPlugin_NetgenLibWrapper ngLib;
  netgen::Mesh * ngMesh = (netgen::Mesh*) ngLib._ngMesh;

  Box<3> bb = occgeo.GetBoundingBox();
  bb.Increase (bb.Diam()/10);
  ngMesh->SetLocalH (bb.PMin(), bb.PMax(), netgen::mparam.grading);
  ngMesh->SetGlobalH (netgen::mparam.maxh);

  vector< const SMDS_MeshNode* > nodeVec;
  problem = addSegmentsToMesh( *ngMesh, occgeo, wires, helper, nodeVec );
  if ( problem && !problem->IsOK() )
    return error( problem );

  // -------------------------
  // Generate surface mesh
  // -------------------------

  char *optstr = 0;
  int startWith = MESHCONST_MESHSURFACE;
  int endWith   = MESHCONST_OPTSURFACE;
  int err = 1;

  try {
#if (OCC_VERSION_MAJOR << 16 | OCC_VERSION_MINOR << 8 | OCC_VERSION_MAINTENANCE) > 0x060100
    OCC_CATCH_SIGNALS;
#endif
    err = netgen::OCCGenerateMesh(occgeo, ngMesh, startWith, endWith, optstr);
#ifdef WITH_SMESH_CANCEL_COMPUTE
    if(netgen::multithread.terminate)
      return false;
#endif
    if ( err )
      error(SMESH_Comment("Error in netgen::OCCGenerateMesh() at ") << netgen::multithread.task);
  }
  catch (Standard_Failure& ex)
  {
    SMESH_Comment str("Exception in  netgen::OCCGenerateMesh()");
    str << " at " << netgen::multithread.task
        << ": " << ex.DynamicType()->Name();
    if ( ex.GetMessageString() && strlen( ex.GetMessageString() ))
      str << ": " << ex.GetMessageString();
    error(str);
  }
  catch (...) {
    SMESH_Comment str("Exception in  netgen::OCCGenerateMesh()");
    str << " at " << netgen::multithread.task;
    error(str);
  }

  // ----------------------------------------------------
  // Fill the SMESHDS with the generated nodes and faces
  // ----------------------------------------------------

  int nbNodes = ngMesh->GetNP();
  int nbFaces = ngMesh->GetNSE();

  int nbInputNodes = nodeVec.size();
  nodeVec.resize( nbNodes, 0 );

  // add nodes
  for ( int i = nbInputNodes + 1; i <= nbNodes; ++i )
  {
    const MeshPoint& ngPoint = ngMesh->Point(i);
#ifdef NETGEN_NEW
    SMDS_MeshNode * node = meshDS->AddNode(ngPoint(0), ngPoint(1), ngPoint(2));
#else
    SMDS_MeshNode * node = meshDS->AddNode(ngPoint.X(), ngPoint.Y(), ngPoint.Z());
#endif
    nodeVec[ i-1 ] = node;
  }

  // create faces
  bool reverse = ( aShape.Orientation() == TopAbs_REVERSED );
  int i,j;
  for ( i = 1; i <= nbFaces ; ++i )
  {
    const Element2d& elem = ngMesh->SurfaceElement(i);
    vector<const SMDS_MeshNode*> nodes( elem.GetNP() );
    for (j=1; j <= elem.GetNP(); ++j)
    {
      int pind = elem.PNum(j);
      if ( pind-1 < 0 )
        break;
      const SMDS_MeshNode* node = nodeVec.at(pind-1);
      if ( reverse )
        nodes[ nodes.size()-j ] = node;
      else
        nodes[ j-1 ] = node;
      if ( node->GetPosition()->GetTypeOfPosition() == SMDS_TOP_3DSPACE )
      {
        const PointGeomInfo& pgi = elem.GeomInfoPi(j);
        meshDS->SetNodeOnFace((SMDS_MeshNode*)node, faceID, pgi.u, pgi.v);
      }
    }
    if ( j > elem.GetNP() )
    {
      SMDS_MeshFace* face = 0;
      if ( elem.GetType() == TRIG )
        face = helper.AddFace(nodes[0],nodes[1],nodes[2]);
      else
        face = helper.AddFace(nodes[0],nodes[1],nodes[2],nodes[3]);
    }
  }

  return !err;
}

#ifdef WITH_SMESH_CANCEL_COMPUTE
void NETGENPlugin_NETGEN_2D_ONLY::CancelCompute()
{
  SMESH_Algo::CancelCompute();
  netgen::multithread.terminate = 1;
}
#endif

//=============================================================================
/*!
 *
 */
//=============================================================================

bool NETGENPlugin_NETGEN_2D_ONLY::Evaluate(SMESH_Mesh& aMesh,
                                           const TopoDS_Shape& aShape,
                                           MapShapeNbElems& aResMap)
{
  TopoDS_Face F = TopoDS::Face(aShape);
  if(F.IsNull())
    return false;

  // collect info from edges
  int nb0d = 0, nb1d = 0;
  bool IsQuadratic = false;
  bool IsFirst = true;
  double fullLen = 0.0;
  TopTools_MapOfShape tmpMap;
  for (TopExp_Explorer exp(F, TopAbs_EDGE); exp.More(); exp.Next()) {
    TopoDS_Edge E = TopoDS::Edge(exp.Current());
    if( tmpMap.Contains(E) )
      continue;
    tmpMap.Add(E);
    SMESH_subMesh *aSubMesh = aMesh.GetSubMesh(exp.Current());
    MapShapeNbElemsItr anIt = aResMap.find(aSubMesh);
    if( anIt==aResMap.end() ) {
      SMESH_subMesh *sm = aMesh.GetSubMesh(F);
      SMESH_ComputeErrorPtr& smError = sm->GetComputeError();
      smError.reset( new SMESH_ComputeError(COMPERR_ALGO_FAILED,"Submesh can not be evaluated",this));
      return false;
    }
    std::vector<int> aVec = (*anIt).second;
    nb0d += aVec[SMDSEntity_Node];
    nb1d += Max(aVec[SMDSEntity_Edge],aVec[SMDSEntity_Quad_Edge]);
    double aLen = SMESH_Algo::EdgeLength(E);
    fullLen += aLen;
    if(IsFirst) {
      IsQuadratic = (aVec[SMDSEntity_Quad_Edge] > aVec[SMDSEntity_Edge]);
      IsFirst = false;
    }
  }
  tmpMap.Clear();

  // compute edge length
  double ELen = 0;
  if (_hypLengthFromEdges || !_hypLengthFromEdges && !_hypMaxElementArea) {
    if ( nb1d > 0 )
      ELen = fullLen / nb1d;
  }
  if ( _hypMaxElementArea ) {
    double maxArea = _hypMaxElementArea->GetMaxArea();
    ELen = sqrt(2. * maxArea/sqrt(3.0));
  }
  GProp_GProps G;
  BRepGProp::SurfaceProperties(F,G);
  double anArea = G.Mass();

  const int hugeNb = numeric_limits<int>::max()/10;
  if ( anArea / hugeNb > ELen*ELen )
  {
    SMESH_subMesh *sm = aMesh.GetSubMesh(F);
    SMESH_ComputeErrorPtr& smError = sm->GetComputeError();
    smError.reset( new SMESH_ComputeError(COMPERR_ALGO_FAILED,"Submesh can not be evaluated.\nToo small element length",this));
    return false;
  }
  int nbFaces = (int) ( anArea / ( ELen*ELen*sqrt(3.) / 4 ) );
  int nbNodes = (int) ( ( nbFaces*3 - (nb1d-1)*2 ) / 6 + 1 );
  std::vector<int> aVec(SMDSEntity_Last);
  for(int i=SMDSEntity_Node; i<SMDSEntity_Last; i++) aVec[i]=0;
  if( IsQuadratic ) {
    aVec[SMDSEntity_Node] = nbNodes;
    aVec[SMDSEntity_Quad_Triangle] = nbFaces;
  }
  else {
    aVec[SMDSEntity_Node] = nbNodes;
    aVec[SMDSEntity_Triangle] = nbFaces;
  }
  SMESH_subMesh *sm = aMesh.GetSubMesh(F);
  aResMap.insert(std::make_pair(sm,aVec));

  return true;
}