// Created on: 1995-01-17
// Created by: Remi LEQUETTE
// Copyright (c) 1995-1999 Matra Datavision
// Copyright (c) 1999-2014 OPEN CASCADE SAS
//
// This file is part of Open CASCADE Technology software library.
//
// This library is free software; you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License version 2.1 as published
// by the Free Software Foundation, with special exception defined in the file
// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
// distribution for complete text of the license and disclaimer of any warranty.
//
// Alternatively, this file may be used under the terms of Open CASCADE
// commercial license or contractual agreement.

#include <AppDef_BSplineCompute.hxx>
#include <AppDef_Variational.hxx>
#include <AppParCurves_ConstraintCouple.hxx>
#include <NCollection_Array1.hxx>
#include <NCollection_HArray1.hxx>
#include <BSplCLib.hxx>
#include <Geom_BSplineCurve.hxx>
#include <Geom_BSplineSurface.hxx>
#include <GeomAPI_PointsToBSpline.hxx>
#include <GeomAPI_PointsToBSplineSurface.hxx>
#include <GeomFill_AppSurf.hxx>
#include <GeomFill_Line.hxx>
#include <GeomFill_SectionGenerator.hxx>
#include <gp_Pnt.hxx>
#include <math_Vector.hxx>
#include <StdFail_NotDone.hxx>
#include <AppDef_BSpParLeastSquareOfMyBSplGradientOfBSplineCompute.hxx>

static void BuildParameters(const AppDef_MultiLine&          theLine,
                            const Approx_ParametrizationType theParT,
                            NCollection_Array1<double>&      thePars)
{
  int       i, j, nbP3d = theLine.NbPoints();
  double    dist;
  int       firstP = 1, lastP = theLine.NbMultiPoints();
  const int aNbp = lastP - firstP + 1;

  if (aNbp == 2)
  {
    thePars(firstP) = 0.0;
    thePars(lastP)  = 1.0;
  }
  else if (theParT == Approx_ChordLength || theParT == Approx_Centripetal)
  {

    thePars(firstP) = 0.0;
    dist            = 0.0;

    for (i = firstP + 1; i <= lastP; i++)
    {
      AppDef_MultiPointConstraint aMPC  = theLine.Value(i - 1);
      AppDef_MultiPointConstraint aMPC1 = theLine.Value(i);

      dist = 0.0;
      for (j = 1; j <= nbP3d; j++)
      {
        const gp_Pnt &aP1 = aMPC.Point(j), &aP2 = aMPC1.Point(j);
        dist += aP2.SquareDistance(aP1);
      }

      dist = std::sqrt(dist);
      if (theParT == Approx_ChordLength)
      {
        thePars(i) = thePars(i - 1) + dist;
      }
      else
      { // Par == Approx_Centripetal
        thePars(i) = thePars(i - 1) + std::sqrt(dist);
      }
    }
    for (i = firstP; i <= lastP; i++)
      thePars(i) /= thePars(lastP);
  }
  else
  {
    for (i = firstP; i <= lastP; i++)
    {
      thePars(i) = (double(i) - firstP) / (double(lastP - double(firstP)));
    }
  }
}

static void BuildPeriodicTangent(const AppDef_MultiLine&           theLine,
                                 const NCollection_Array1<double>& thePars,
                                 math_Vector&                      theTang)
{
  int firstpt = 1, lastpt = theLine.NbMultiPoints();
  int nbpoints = lastpt - firstpt + 1;
  //
  if (nbpoints <= 2)
  {
    return;
  }
  //
  int i, nnpol, nnp = std::min(nbpoints, 9);
  nnpol                         = nnp;
  int                     lastp = std::min(lastpt, firstpt + nnp - 1);
  double                  U;
  AppParCurves_Constraint Cons = AppParCurves_TangencyPoint;
  if (nnp <= 4)
  {
    Cons = AppParCurves_PassPoint;
  }
  int         nbP = 3 * theLine.NbPoints();
  math_Vector V1(1, nbP), V2(1, nbP);
  math_Vector P1(firstpt, lastp);
  //
  for (i = firstpt; i <= lastp; i++)
  {
    P1(i) = thePars(i);
  }

  AppDef_BSpParLeastSquareOfMyBSplGradientOfBSplineCompute SQ1(theLine,
                                                               firstpt,
                                                               lastp,
                                                               Cons,
                                                               Cons,
                                                               nnpol);
  SQ1.Perform(P1);
  const AppParCurves_MultiCurve& C1 = SQ1.BezierValue();
  U                                 = 0.0;
  int j, nbP3d = theLine.NbPoints();

  gp_Pnt aP;
  gp_Vec aV;
  j = 1;
  for (i = 1; i <= nbP3d; i++)
  {
    C1.D1(i, U, aP, aV);
    V1(j)     = aV.X();
    V1(j + 1) = aV.Y();
    V1(j + 2) = aV.Z();
    j += 3;
  }

  int firstp = std::max(firstpt, lastpt - nnp + 1);

  if (firstp == firstpt && lastp == lastpt)
  {
    U = 1.0;
    j = 1;
    for (i = 1; i <= nbP3d; i++)
    {
      C1.D1(i, U, aP, aV);
      V2(j)     = aV.X();
      V2(j + 1) = aV.Y();
      V2(j + 2) = aV.Z();
      j += 3;
    }
  }
  else
  {
    AppDef_BSpParLeastSquareOfMyBSplGradientOfBSplineCompute SQ2(theLine,
                                                                 firstp,
                                                                 lastpt,
                                                                 Cons,
                                                                 Cons,
                                                                 nnpol);

    math_Vector P2(firstp, lastpt);
    for (i = firstp; i <= lastpt; i++)
      P2(i) = thePars(i);
    SQ2.Perform(P2);

    const AppParCurves_MultiCurve& C2 = SQ2.BezierValue();
    U                                 = 1.0;
    j                                 = 1;
    for (i = 1; i <= nbP3d; i++)
    {
      C2.D1(i, U, aP, aV);
      V2(j)     = aV.X();
      V2(j + 1) = aV.Y();
      V2(j + 2) = aV.Z();
      j += 3;
    }
  }

  theTang = 0.5 * (V1 + V2);
}

//=================================================================================================

GeomAPI_PointsToBSplineSurface::GeomAPI_PointsToBSplineSurface()
    : myIsDone(false)
{
}

//=================================================================================================

GeomAPI_PointsToBSplineSurface::GeomAPI_PointsToBSplineSurface(
  const NCollection_Array2<gp_Pnt>& Points,
  const int                         DegMin,
  const int                         DegMax,
  const GeomAbs_Shape               Continuity,
  const double                      Tol3D)
    : myIsDone(false)
{
  Init(Points, DegMin, DegMax, Continuity, Tol3D);
}

//=================================================================================================

GeomAPI_PointsToBSplineSurface::GeomAPI_PointsToBSplineSurface(
  const NCollection_Array2<gp_Pnt>& Points,
  const Approx_ParametrizationType  ParType,
  const int                         DegMin,
  const int                         DegMax,
  const GeomAbs_Shape               Continuity,
  const double                      Tol3D)
    : myIsDone(false)
{
  Init(Points, ParType, DegMin, DegMax, Continuity, Tol3D);
}

//=================================================================================================

GeomAPI_PointsToBSplineSurface::GeomAPI_PointsToBSplineSurface(
  const NCollection_Array2<gp_Pnt>& Points,
  const double                      Weight1,
  const double                      Weight2,
  const double                      Weight3,
  const int                         DegMax,
  const GeomAbs_Shape               Continuity,
  const double                      Tol3D)
    : myIsDone(false)
{
  Init(Points, Weight1, Weight2, Weight3, DegMax, Continuity, Tol3D);
}

//=================================================================================================

GeomAPI_PointsToBSplineSurface::GeomAPI_PointsToBSplineSurface(
  const NCollection_Array2<double>& ZPoints,
  const double                      X0,
  const double                      dX,
  const double                      Y0,
  const double                      dY,
  const int                         DegMin,
  const int                         DegMax,
  const GeomAbs_Shape               Continuity,
  const double                      Tol3D)
    : myIsDone(false)
{
  Init(ZPoints, X0, dX, Y0, dY, DegMin, DegMax, Continuity, Tol3D);
}

//=================================================================================================

void GeomAPI_PointsToBSplineSurface::Interpolate(const NCollection_Array2<gp_Pnt>& Points,
                                                 const bool                        thePeriodic)
{
  Interpolate(Points, Approx_ChordLength, thePeriodic);
}

//=================================================================================================

void GeomAPI_PointsToBSplineSurface::Interpolate(const NCollection_Array2<gp_Pnt>& Points,
                                                 const Approx_ParametrizationType  ParType,
                                                 const bool                        thePeriodic)
{
  int DegMin, DegMax;
  DegMin = DegMax     = 3;
  GeomAbs_Shape CC    = GeomAbs_C2;
  double        Tol3d = -1.0;
  Init(Points, ParType, DegMin, DegMax, CC, Tol3d, thePeriodic);
}

//=================================================================================================

void GeomAPI_PointsToBSplineSurface::Init(const NCollection_Array2<gp_Pnt>& Points,
                                          const int                         DegMin,
                                          const int                         DegMax,
                                          const GeomAbs_Shape               Continuity,
                                          const double                      Tol3D)
{
  Init(Points, Approx_ChordLength, DegMin, DegMax, Continuity, Tol3D);
}

//=================================================================================================

void GeomAPI_PointsToBSplineSurface::Init(const NCollection_Array2<gp_Pnt>& Points,
                                          const Approx_ParametrizationType  ParType,
                                          const int                         DegMin,
                                          const int                         DegMax,
                                          const GeomAbs_Shape               Continuity,
                                          const double                      Tol3D,
                                          const bool                        thePeriodic)
{
  int Imin = Points.LowerRow();
  int Imax = Points.UpperRow();
  int Jmin = Points.LowerCol();
  int Jmax = Points.UpperCol();

  double Tol2D = Tol3D;

  // first approximate the U isos:
  int add = 1;
  if (thePeriodic)
  {
    add = 2;
  }
  AppDef_MultiLine Line(Jmax - Jmin + 1);
  int              i, j;

  for (j = Jmin; j <= Jmax; j++)
  {
    AppDef_MultiPointConstraint MP(Imax - Imin + add, 0);
    for (i = Imin; i <= Imax; i++)
    {
      MP.SetPoint(i, Points(i, j));
    }
    if (thePeriodic)
    {
      MP.SetPoint(Imax + 1, Points(1, j));
    }
    Line.SetValue(j, MP);
  }

  int  nbit       = 2;
  bool UseSquares = false;
  if (Tol3D <= 1.e-3)
    UseSquares = true;

  AppDef_BSplineCompute TheComputer(DegMin, DegMax, Tol3D, Tol2D, nbit, true, ParType, UseSquares);

  switch (Continuity)
  {
    case GeomAbs_C0:
      TheComputer.SetContinuity(0);
      break;

    case GeomAbs_G1:
    case GeomAbs_C1:
      TheComputer.SetContinuity(1);
      break;

    case GeomAbs_G2:
    case GeomAbs_C2:
      TheComputer.SetContinuity(2);
      break;

    default:
      TheComputer.SetContinuity(3);
  }

  if (Tol3D <= 0.0)
  {
    TheComputer.Interpol(Line);
  }
  else
  {
    TheComputer.Perform(Line);
  }

  const AppParCurves_MultiBSpCurve& TheCurve = TheComputer.Value();

  int                               VDegree = TheCurve.Degree();
  NCollection_Array1<gp_Pnt>        Poles(1, TheCurve.NbPoles());
  const NCollection_Array1<double>& VKnots = TheCurve.Knots();
  const NCollection_Array1<int>&    VMults = TheCurve.Multiplicities();

  int              nbisosu = Imax - Imin + add;
  AppDef_MultiLine Line2(nbisosu);

  for (i = 1; i <= nbisosu; i++)
  {
    TheCurve.Curve(i, Poles);
    AppDef_MultiPointConstraint MP(Poles.Upper(), 0);
    for (j = 1; j <= Poles.Upper(); j++)
    {
      MP.SetPoint(j, Poles(j));
    }
    Line2.SetValue(i, MP);
  }

  // approximate the resulting poles:

  AppDef_BSplineCompute TheComputer2(DegMin, DegMax, Tol3D, Tol2D, nbit, true, ParType, UseSquares);
  if (Tol3D <= 0.0)
  {
    if (thePeriodic)
    {
      TheComputer2.SetPeriodic(thePeriodic);
    }
    TheComputer2.Interpol(Line2);
  }
  else
  {
    if (thePeriodic && Line2.NbMultiPoints() > 2)
    {
      TheComputer2.SetPeriodic(thePeriodic);
      //
      NCollection_Array1<double> aPars(1, Line2.NbMultiPoints());
      BuildParameters(Line2, ParType, aPars);
      math_Vector aTang(1, 3 * Poles.Upper());
      BuildPeriodicTangent(Line2, aPars, aTang);
      int ind = 1;
      TheCurve.Curve(ind, Poles);
      AppDef_MultiPointConstraint MP1(Poles.Upper(), 0);
      for (j = 1; j <= Poles.Upper(); j++)
      {
        MP1.SetPoint(j, Poles(j));
        int    k = 3 * (j - 1);
        gp_Vec aT(aTang(k + 1), aTang(k + 2), aTang(k + 3));
        MP1.SetTang(j, aT);
      }
      Line2.SetValue(ind, MP1);
      //
      ind = Line2.NbMultiPoints();
      TheCurve.Curve(ind, Poles);
      AppDef_MultiPointConstraint MP2(Poles.Upper(), 0);
      for (j = 1; j <= Poles.Upper(); j++)
      {
        MP2.SetPoint(j, Poles(j));
        int    k = 3 * (j - 1);
        gp_Vec aT(aTang(k + 1), aTang(k + 2), aTang(k + 3));
        MP2.SetTang(j, aT);
      }
      Line2.SetValue(ind, MP2);
    }
    TheComputer2.Perform(Line2);
  }

  const AppParCurves_MultiBSpCurve& TheCurve2 = TheComputer2.Value();

  int                               UDegree = TheCurve2.Degree();
  NCollection_Array1<gp_Pnt>        Poles2(1, TheCurve2.NbPoles());
  const NCollection_Array1<double>& UKnots = TheCurve2.Knots();
  const NCollection_Array1<int>&    UMults = TheCurve2.Multiplicities();

  // computing the surface
  NCollection_Array2<gp_Pnt> ThePoles(1, Poles2.Upper(), 1, Poles.Upper());
  for (j = 1; j <= Poles.Upper(); j++)
  {
    TheCurve2.Curve(j, Poles2);
    for (i = 1; i <= Poles2.Upper(); i++)
    {
      ThePoles(i, j) = Poles2(i);
    }
  }

  mySurface = new Geom_BSplineSurface(ThePoles, UKnots, VKnots, UMults, VMults, UDegree, VDegree);
  if (thePeriodic && Line2.NbMultiPoints() > 2)
  {
    mySurface->SetUPeriodic();
  }

  myIsDone = true;
}

//=================================================================================================

void GeomAPI_PointsToBSplineSurface::Init(const NCollection_Array2<gp_Pnt>& Points,
                                          const double                      Weight1,
                                          const double                      Weight2,
                                          const double                      Weight3,
                                          const int                         DegMax,
                                          const GeomAbs_Shape               Continuity,
                                          const double                      Tol3D)
{
  int Imin = Points.LowerRow();
  int Imax = Points.UpperRow();
  int Jmin = Points.LowerCol();
  int Jmax = Points.UpperCol();

  int nbit = 2;
  if (Tol3D <= 1.e-3)
    nbit = 0;

  // first approximate the U isos:
  int NbPointJ = Jmax - Jmin + 1;
  int NbPointI = Imax - Imin + 1;
  int i, j;

  AppDef_MultiLine Line(NbPointJ);

  for (j = Jmin; j <= Jmax; j++)
  {
    AppDef_MultiPointConstraint MP(NbPointI, 0);
    for (i = Imin; i <= Imax; i++)
    {
      MP.SetPoint(i, Points(i, j));
    }
    Line.SetValue(j, MP);
  }

  occ::handle<NCollection_HArray1<AppParCurves_ConstraintCouple>> TABofCC =
    new NCollection_HArray1<AppParCurves_ConstraintCouple>(1, NbPointJ);
  AppParCurves_Constraint Constraint = AppParCurves_NoConstraint;

  for (i = 1; i <= NbPointJ; ++i)
  {
    AppParCurves_ConstraintCouple ACC(i, Constraint);
    TABofCC->SetValue(i, ACC);
  }

  AppDef_Variational Variation(Line, 1, NbPointJ, TABofCC);

  //===================================
  int  theMaxSegments = 1000;
  bool theWithMinMax  = false;
  //===================================

  Variation.SetMaxDegree(DegMax);
  Variation.SetContinuity(Continuity);
  Variation.SetMaxSegment(theMaxSegments);

  Variation.SetTolerance(Tol3D);
  Variation.SetWithMinMax(theWithMinMax);
  Variation.SetNbIterations(nbit);

  Variation.SetCriteriumWeight(Weight1, Weight2, Weight3);

  if (!Variation.IsCreated())
  {
    return;
  }

  if (Variation.IsOverConstrained())
  {
    return;
  }

  try
  {
    Variation.Approximate();
  }
  catch (Standard_Failure const&)
  {
    return;
  }

  if (!Variation.IsDone())
  {
    return;
  }

  const AppParCurves_MultiBSpCurve& TheCurve = Variation.Value();

  int                               VDegree = TheCurve.Degree();
  NCollection_Array1<gp_Pnt>        Poles(1, TheCurve.NbPoles());
  const NCollection_Array1<double>& VKnots = TheCurve.Knots();
  const NCollection_Array1<int>&    VMults = TheCurve.Multiplicities();

  AppDef_MultiLine Line2(NbPointI);

  for (i = 1; i <= NbPointI; i++)
  {
    TheCurve.Curve(i, Poles);
    AppDef_MultiPointConstraint MP(Poles.Upper(), 0);
    for (j = 1; j <= Poles.Upper(); j++)
    {
      MP.SetPoint(j, Poles(j));
    }
    Line2.SetValue(i, MP);
  }

  occ::handle<NCollection_HArray1<AppParCurves_ConstraintCouple>> TABofCC2 =
    new NCollection_HArray1<AppParCurves_ConstraintCouple>(1, NbPointI);

  for (i = 1; i <= NbPointI; ++i)
  {
    AppParCurves_ConstraintCouple ACC(i, Constraint);
    TABofCC2->SetValue(i, ACC);
  }

  AppDef_Variational Variation2(Line2, 1, NbPointI, TABofCC2);

  Variation2.SetMaxDegree(DegMax);
  Variation2.SetContinuity(Continuity);
  Variation2.SetMaxSegment(theMaxSegments);

  Variation2.SetTolerance(Tol3D);
  Variation2.SetWithMinMax(theWithMinMax);
  Variation2.SetNbIterations(nbit);

  Variation2.SetCriteriumWeight(Weight1, Weight2, Weight3);

  if (!Variation2.IsCreated())
  {
    return;
  }

  if (Variation2.IsOverConstrained())
  {
    return;
  }

  try
  {
    Variation2.Approximate();
  }
  catch (Standard_Failure const&)
  {
    return;
  }

  if (!Variation2.IsDone())
  {
    return;
  }

  const AppParCurves_MultiBSpCurve& TheCurve2 = Variation2.Value();

  int                               UDegree = TheCurve2.Degree();
  NCollection_Array1<gp_Pnt>        Poles2(1, TheCurve2.NbPoles());
  const NCollection_Array1<double>& UKnots = TheCurve2.Knots();
  const NCollection_Array1<int>&    UMults = TheCurve2.Multiplicities();

  // computing the surface
  NCollection_Array2<gp_Pnt> ThePoles(1, Poles2.Upper(), 1, Poles.Upper());
  for (j = 1; j <= Poles.Upper(); j++)
  {
    TheCurve2.Curve(j, Poles2);
    for (i = 1; i <= Poles2.Upper(); i++)
    {
      ThePoles(i, j) = Poles2(i);
    }
  }

  mySurface = new Geom_BSplineSurface(ThePoles, UKnots, VKnots, UMults, VMults, UDegree, VDegree);

  myIsDone = true;
}

//=================================================================================================

void GeomAPI_PointsToBSplineSurface::Interpolate(const NCollection_Array2<double>& ZPoints,
                                                 const double                      X0,
                                                 const double                      dX,
                                                 const double                      Y0,
                                                 const double                      dY)
{
  int DegMin, DegMax;
  DegMin = DegMax     = 3;
  double        Tol3D = -1.0;
  GeomAbs_Shape CC    = GeomAbs_C2;
  Init(ZPoints, X0, dX, Y0, dY, DegMin, DegMax, CC, Tol3D);
}

//=================================================================================================

void GeomAPI_PointsToBSplineSurface::Init(const NCollection_Array2<double>& ZPoints,
                                          const double                      X0,
                                          const double                      dX,
                                          const double                      Y0,
                                          const double                      dY,
                                          const int                         DegMin,
                                          const int                         DegMax,
                                          const GeomAbs_Shape               Continuity,
                                          const double                      Tol3D)
{
  int    Imin = ZPoints.LowerRow();
  int    Imax = ZPoints.UpperRow();
  int    Jmin = ZPoints.LowerCol();
  int    Jmax = ZPoints.UpperCol();
  double length;

  double Tol2D = Tol3D;

  // first approximate the U isos:
  AppDef_MultiLine Line(Jmax - Jmin + 1);
  math_Vector      Param(Jmin, Jmax);
  int              i, j;
  //  double X, Y;
  length = dY * (Jmax - Jmin);

  for (j = Jmin; j <= Jmax; j++)
  {
    AppDef_MultiPointConstraint MP(0, Imax - Imin + 1);
    for (i = Imin; i <= Imax; i++)
    {
      MP.SetPoint2d(i, gp_Pnt2d(0.0, ZPoints(i, j)));
    }
    Param(j) = (double)(j - Jmin) / (double)(Jmax - Jmin);
    Line.SetValue(j, MP);
  }

  AppDef_BSplineCompute TheComputer(Param, DegMin, DegMax, Tol3D, Tol2D, 0, true, true);

  switch (Continuity)
  {
    case GeomAbs_C0:
      TheComputer.SetContinuity(0);
      break;

    case GeomAbs_G1:
    case GeomAbs_C1:
      TheComputer.SetContinuity(1);
      break;

    case GeomAbs_G2:
    case GeomAbs_C2:
      TheComputer.SetContinuity(2);
      break;

    default:
      TheComputer.SetContinuity(3);
  }

  if (Tol3D <= 0.0)
  {
    TheComputer.Interpol(Line);
  }
  else
  {
    TheComputer.Perform(Line);
  }

  const AppParCurves_MultiBSpCurve& TheCurve = TheComputer.Value();

  int                          VDegree = TheCurve.Degree();
  NCollection_Array1<gp_Pnt2d> Poles(1, TheCurve.NbPoles());
  int                          nk = TheCurve.Knots().Length();
  NCollection_Array1<double>   VKnots(1, nk);
  NCollection_Array1<int>      VMults(1, nk);

  // compute Y values for the poles
  NCollection_Array1<double> YPoles(1, Poles.Upper());

  // start with a line
  NCollection_Array1<double> TempPoles(1, 2);
  NCollection_Array1<double> TempKnots(1, 2);
  NCollection_Array1<int>    TempMults(1, 2);
  TempMults.Init(2);
  TempPoles(1) = Y0;
  TempPoles(2) = Y0 + length;
  TempKnots(1) = 0.;
  TempKnots(2) = 1.;

  // increase the Degree
  NCollection_Array1<double> NewTempPoles(1, VDegree + 1);
  NCollection_Array1<double> NewTempKnots(1, 2);
  NCollection_Array1<int>    NewTempMults(1, 2);
  BSplCLib::IncreaseDegree(1,
                           VDegree,
                           false,
                           1,
                           TempPoles,
                           TempKnots,
                           TempMults,
                           NewTempPoles,
                           NewTempKnots,
                           NewTempMults);

  // insert the Knots
  BSplCLib::InsertKnots(VDegree,
                        false,
                        1,
                        NewTempPoles,
                        NewTempKnots,
                        NewTempMults,
                        TheCurve.Knots(),
                        &TheCurve.Multiplicities(),
                        YPoles,
                        VKnots,
                        VMults,
                        Epsilon(1));

  // scale the knots
  for (i = 1; i <= nk; i++)
  {
    VKnots(i) = Y0 + length * VKnots(i);
  }

  int              nbisosu = Imax - Imin + 1;
  AppDef_MultiLine Line2(nbisosu);
  math_Vector      Param2(1, nbisosu);
  length = dX * (Imax - Imin);

  for (i = 1; i <= nbisosu; i++)
  {
    TheCurve.Curve(i, Poles);
    AppDef_MultiPointConstraint MP(0, Poles.Upper());
    for (j = 1; j <= Poles.Upper(); j++)
    {
      MP.SetPoint2d(j, gp_Pnt2d(0.0, Poles(j).Y()));
    }
    Param2(i) = (double)(i - 1) / (double)(nbisosu - 1);
    Line2.SetValue(i, MP);
  }

  // approximate the resulting poles:

  AppDef_BSplineCompute TheComputer2(Param2, DegMin, DegMax, Tol3D, Tol2D, 0, true, true);
  if (Tol3D <= 0.0)
  {
    TheComputer2.Interpol(Line2);
  }
  else
  {
    TheComputer2.Perform(Line2);
  }

  const AppParCurves_MultiBSpCurve& TheCurve2 = TheComputer2.Value();

  int                          UDegree = TheCurve2.Degree();
  NCollection_Array1<gp_Pnt2d> Poles2(1, TheCurve2.NbPoles());
  int                          nk2 = TheCurve2.Knots().Length();
  NCollection_Array1<double>   UKnots(1, nk2);
  NCollection_Array1<int>      UMults(1, nk2);

  // compute X values for the poles
  NCollection_Array1<double> XPoles(1, Poles2.Upper());

  // start with a line
  TempPoles(1) = X0;
  TempPoles(2) = X0 + length;
  TempKnots(1) = 0.;
  TempKnots(2) = 1.;
  TempMults(1) = TempMults(2) = 2;

  // increase the Degree
  NCollection_Array1<double> NewTempPoles2(1, UDegree + 1);
  BSplCLib::IncreaseDegree(1,
                           UDegree,
                           false,
                           1,
                           TempPoles,
                           TempKnots,
                           TempMults,
                           NewTempPoles2,
                           NewTempKnots,
                           NewTempMults);

  // insert the Knots
  BSplCLib::InsertKnots(UDegree,
                        false,
                        1,
                        NewTempPoles2,
                        NewTempKnots,
                        NewTempMults,
                        TheCurve2.Knots(),
                        &TheCurve2.Multiplicities(),
                        XPoles,
                        UKnots,
                        UMults,
                        Epsilon(1));

  // scale the knots
  for (i = 1; i <= nk2; i++)
  {
    UKnots(i) = X0 + length * UKnots(i);
  }

  // creating the surface
  NCollection_Array2<gp_Pnt> ThePoles(1, Poles2.Upper(), 1, Poles.Upper());

  for (j = 1; j <= Poles.Upper(); j++)
  {
    TheCurve2.Curve(j, Poles2);
    for (i = 1; i <= Poles2.Upper(); i++)
    {
      ThePoles(i, j).SetCoord(XPoles(i), YPoles(j), Poles2(i).Y());
    }
  }

  mySurface = new Geom_BSplineSurface(ThePoles, UKnots, VKnots, UMults, VMults, UDegree, VDegree);

  myIsDone = true;
}

//=======================================================================
// function : occ::handle<Geom_BSplineSurface>&
// purpose  :
//=======================================================================

const occ::handle<Geom_BSplineSurface>& GeomAPI_PointsToBSplineSurface::Surface() const
{
  StdFail_NotDone_Raise_if(!myIsDone, "GeomAPI_PointsToBSplineSurface: Surface not done");

  return mySurface;
}

//=================================================================================================

GeomAPI_PointsToBSplineSurface::operator occ::handle<Geom_BSplineSurface>() const
{
  return Surface();
}

//=================================================================================================

bool GeomAPI_PointsToBSplineSurface::IsDone() const
{
  return myIsDone;
}
