#include <mystdlib.h>


#include <linalg.hpp>
#include <csg.hpp>


namespace netgen
{

  double 
  QuadraticSurface :: CalcFunctionValue (const Point<3> & p) const
  {
    return p(0) * (cxx * p(0) + cxy * p(1) + cxz * p(2) + cx) +
      p(1) * (cyy * p(1) + cyz * p(2) + cy) +
      p(2) * (czz * p(2) + cz) + c1;
  }

  void 
  QuadraticSurface :: CalcGradient (const Point<3> & p, Vec<3> & grad) const
  {
    grad(0) = 2 * cxx * p(0) + cxy * p(1) + cxz * p(2) + cx;
    grad(1) = 2 * cyy * p(1) + cxy * p(0) + cyz * p(2) + cy;
    grad(2) = 2 * czz * p(2) + cxz * p(0) + cyz * p(1) + cz;
  }

  void 
  QuadraticSurface :: CalcHesse (const Point<3> & /* p */, Mat<3> & hesse) const
  {
    hesse(0,0) = 2 * cxx;
    hesse(1,1) = 2 * cyy;
    hesse(2,2) = 2 * czz;
    hesse(0,1) = hesse(1,0) = cxy;
    hesse(0,2) = hesse(2,0) = cxz;
    hesse(1,2) = hesse(2,1) = cyz;
  }


  void QuadraticSurface :: Read (istream & ist)
  {
    ist >> cxx >> cyy >> czz >> cxy >> cxz >> cyz >> cx >> cy >> cz >> c1;
  }

  void QuadraticSurface :: Print (ostream & ost) const
  {
    ost << cxx << "  " << cyy << "  " << czz << "  "
        << cxy << "  " << cxz << "  " << cyz << "  "
        << cx << "  " << cy << "  " << cz << "  "
        << c1;
  }


  void QuadraticSurface :: PrintCoeff (ostream & ost) const
  {
    ost << " cxx = " << cxx
        << " cyy = " << cyy
        << " czz = " << czz
        << " cxy = " << cxy
        << " cxz = " << cxz
        << " cyz = " << cyz
        << " cx = " << cx
        << " cy = " << cy
        << " cz = " << cz
        << " c1 = " << c1 << endl;
  }



  Point<3> QuadraticSurface :: GetSurfacePoint () const
  {
    MyError ("GetSurfacePoint called for QuadraticSurface");
    return Point<3> (0, 0, 0);
  }


  Plane :: Plane (const Point<3> & ap, Vec<3> an)
  {
    eps_base = 1e-8;

    p = ap;
    n = an;
    n.Normalize();

    cxx = cyy = czz = cxy = cxz = cyz = 0;
    cx = n(0); cy = n(1); cz = n(2);
    c1 = - (cx * p(0) + cy * p(1) + cz * p(2));
  }

  Primitive * Plane :: Copy () const
  {
    return new Plane (p, n);
  }

  void Plane :: Transform (Transformation<3> & trans)
  {
    Point<3> hp;
    Vec<3> hn;
    trans.Transform (p, hp);
    trans.Transform (n, hn);
    p = hp;
    n = hn;

    cxx = cyy = czz = cxy = cxz = cyz = 0;
    cx = n(0); cy = n(1); cz = n(2);
    c1 = - (cx * p(0) + cy * p(1) + cz * p(2));
  }



  void Plane :: GetPrimitiveData (const char *& classname, 
                                  Array<double> & coeffs) const
  {
    classname = "plane";
    coeffs.SetSize (6);
    coeffs.Elem(1) = p(0);
    coeffs.Elem(2) = p(1);
    coeffs.Elem(3) = p(2);
    coeffs.Elem(4) = n(0);
    coeffs.Elem(5) = n(1);
    coeffs.Elem(6) = n(2);
  }

  void Plane :: SetPrimitiveData (Array<double> & coeffs)
  {
    p(0) = coeffs.Elem(1);
    p(1) = coeffs.Elem(2);
    p(2) = coeffs.Elem(3);
    n(0) = coeffs.Elem(4);
    n(1) = coeffs.Elem(5);
    n(2) = coeffs.Elem(6);

    n.Normalize();

    cxx = cyy = czz = cxy = cxz = cyz = 0;
    cx = n(0); cy = n(1); cz = n(2);
    c1 = - (cx * p(0) + cy * p(1) + cz * p(2));
  }

  Primitive * Plane :: CreateDefault ()
  {
    return new Plane (Point<3> (0,0,0), Vec<3> (0,0,1));
  }


  int Plane :: IsIdentic (const Surface & s2, int & inv, double eps) const
  {
    const Plane * ps2 = dynamic_cast<const Plane*>(&s2);

    if(ps2)
      {
        Point<3> pp2 = ps2->GetSurfacePoint();
        Vec<3> n2 = s2.GetNormalVector(pp2);

        if(fabs(n*n2) < 1.-eps_base)
          return 0;

        if (fabs (s2.CalcFunctionValue(p)) > eps) return 0;
      }
    else
      {
        //(*testout) << "pos1" << endl;
        if (fabs (s2.CalcFunctionValue(p)) > eps) return 0;
        Vec<3> hv1, hv2;
        hv1 = n.GetNormal ();
        hv2 = Cross (n, hv1);
      
        Point<3> hp = p + hv1;
        //(*testout) << "pos2" << endl;
        //(*testout) << "eps " << eps << " s2.CalcFunctionValue(hp) " << s2.CalcFunctionValue(hp) << endl;
        if (fabs (s2.CalcFunctionValue(hp)) > eps) return 0;
        //(*testout) << "pos3" << endl;
        hp = p + hv2;
        if (fabs (s2.CalcFunctionValue(hp)) > eps) return 0;
      }

    //(*testout) << "pos4" << endl;
    Vec<3> n1, n2;
    n1 = GetNormalVector (p);
    n2 = s2.GetNormalVector (p);
    inv = (n1 * n2 < 0);
    //(*testout) << "inv " << inv << endl;
    return 1;
  }



  void Plane :: DefineTangentialPlane (const Point<3> & ap1, const Point<3> & ap2)
  {
    Surface::DefineTangentialPlane (ap1, ap2);
  }


  void Plane :: ToPlane (const Point<3> & p3d, 
                         Point<2> & pplane, 
                         double h, int & zone) const
  {
    Vec<3> p1p;

    p1p = p3d - p1;
    p1p /= h;
    pplane(0) = p1p * ex;
    pplane(1) = p1p * ey;
    zone = 0;
  }

  void Plane :: FromPlane (const Point<2> & pplane, Point<3> & p3d, double h) const
  {
    /*
      Vec<3> p1p;
      Point<2> pplane2 = pplane;
  
      pplane2 *= h;
      p1p = pplane2(0) * ex + pplane2(1) * ey;
      p3d = p1 + p1p;
    */
    p3d = p1 + (h * pplane(0)) * ex + (h * pplane(1)) * ey;
  }


  void Plane :: Project (Point<3> & p3d) const
  {
    double val = Plane::CalcFunctionValue (p3d);
    p3d -= val * n;
  }

  INSOLID_TYPE Plane :: BoxInSolid (const BoxSphere<3> & box) const
  {
    int i;
    double val;
    Point<3> pp;

    val = Plane::CalcFunctionValue (box.Center());
    if (val > box.Diam() / 2) return IS_OUTSIDE;
    if (val < -box.Diam() / 2) return IS_INSIDE;

    if (val > 0)
      {
        /*
          double modify = 
          ((box.MaxX()-box.MinX()) * fabs (cx) + 
          (box.MaxY()-box.MinY()) * fabs (cy) + 
          (box.MaxZ()-box.MinZ()) * fabs (cz)) / 2;
        */
        Vec<3> vdiag = box.PMax() - box.PMin();
        double modify = (vdiag(0) * fabs (cx) + 
                         vdiag(1) * fabs (cy) + 
                         vdiag(2) * fabs (cz) ) / 2;

        if (val - modify < 0)
          return DOES_INTERSECT;
        return IS_OUTSIDE;

        // only outside or intersect possible
        for (i = 0; i < 8; i++)
          {
            pp = box.GetPointNr (i);
            val = Plane::CalcFunctionValue (pp);
            if (val < 0) 
              return DOES_INTERSECT;
          }
        return IS_OUTSIDE;
      }
    else
      {
        /*
          double modify = 
          ((box.MaxX()-box.MinX()) * fabs (cx) + 
          (box.MaxY()-box.MinY()) * fabs (cy) + 
          (box.MaxZ()-box.MinZ()) * fabs (cz)) / 2;
        */
        Vec<3> vdiag = box.PMax() - box.PMin();
        double modify =  (vdiag(0) * fabs (cx) + 
                          vdiag(1) * fabs (cy) + 
                          vdiag(2) * fabs (cz) ) / 2;
        if (val + modify > 0)
          return DOES_INTERSECT;
        return IS_INSIDE;


        // only inside or intersect possible
        for (i = 0; i < 8; i++)
          {
            pp = box.GetPointNr (i);
            val = Plane::CalcFunctionValue (pp);
            if (val > 0) 
              return DOES_INTERSECT;
          }
        return IS_INSIDE;
      }



    /*
      for (i = 1; i <= 8; i++)
      {
      box.GetPointNr (i, p);
      val = CalcFunctionValue (p);
      if (val > 0) inside = 0;
      if (val < 0) outside = 0;
      }

      if (inside) return IS_INSIDE;
      if (outside) return IS_OUTSIDE;
      return DOES_INTERSECT;
    */
  }



  // double Plane :: CalcFunctionValue (const Point<3> & p3d) const
  // {
  //   return cx * p3d(0) + cy * p3d(1) + cz * p3d(2) + c1;
  // }

  void Plane :: CalcGradient (const Point<3> & /* p */, Vec<3> & grad) const
  {
    grad(0) = cx;
    grad(1) = cy;
    grad(2) = cz;
  }

  void Plane :: CalcHesse (const Point<3> & /* p */, Mat<3> & hesse) const
  {
    hesse = 0;
  }

  double Plane :: HesseNorm () const
  {
    return 0;
  }


  Point<3> Plane :: GetSurfacePoint () const
  {
    return p;
  }


  void Plane :: GetTriangleApproximation 
  (TriangleApproximation & tas, 
   const Box<3> & boundingbox, double /* facets */) const
  {
    // find triangle, such that
    // boundingbox \cap plane is contained in it

    Point<3> c = boundingbox.Center();
    double r = boundingbox.Diam();

    Project (c);
    Vec<3> t1 = n.GetNormal();
    Vec<3> t2 = Cross (n, t1);

    t1.Normalize();
    t2.Normalize();

    tas.AddPoint (c + (-0.5 * r) * t2 + (sqrt(0.75) * r) * t1);
    tas.AddPoint (c + (-0.5 * r) * t2 + (-sqrt(0.75) * r) * t1);
    tas.AddPoint (c +  r * t2);

    tas.AddTriangle (TATriangle (0, 0, 1, 2));
  }




  Sphere :: Sphere (const Point<3> & ac, double ar)
  {
    c = ac;
    r = ar;
  
    cxx = cyy = czz = 0.5 / r;
    cxy = cxz = cyz = 0;
    cx = - c(0) / r;
    cy = - c(1) / r;
    cz = - c(2) / r;
    c1 = (c(0) * c(0) + c(1) * c(1) + c(2) * c(2)) / (2 * r) - r / 2;
  }

  void Sphere :: GetPrimitiveData (const char *& classname, Array<double> & coeffs) const
  {
    classname = "sphere";
    coeffs.SetSize (4);
    coeffs.Elem(1) = c(0);
    coeffs.Elem(2) = c(1);
    coeffs.Elem(3) = c(2);
    coeffs.Elem(4) = r;
  }

  void Sphere :: SetPrimitiveData (Array<double> & coeffs)
  {
    c(0) = coeffs.Elem(1);
    c(1) = coeffs.Elem(2);
    c(2) = coeffs.Elem(3);
    r = coeffs.Elem(4);

    cxx = cyy = czz = 0.5 / r;
    cxy = cxz = cyz = 0;
    cx = - c(0) / r;
    cy = - c(1) / r;
    cz = - c(2) / r;
    c1 = (c(0) * c(0) + c(1) * c(1) + c(2) * c(2)) / (2 * r) - r / 2;
  }

  Primitive * Sphere :: CreateDefault ()
  {
    return new Sphere (Point<3> (0,0,0), 1);
  }



  Primitive * Sphere :: Copy () const
  {
    return new Sphere (c, r);
  }

  void Sphere :: Transform (Transformation<3> & trans)
  {
    Point<3> hp;
    trans.Transform (c, hp);
    c = hp;

    cxx = cyy = czz = 0.5 / r;
    cxy = cxz = cyz = 0;
    cx = - c(0) / r;
    cy = - c(1) / r;
    cz = - c(2) / r;
    c1 = (c(0) * c(0) + c(1) * c(1) + c(2) * c(2)) / (2 * r) - r / 2;
  }




  int Sphere :: IsIdentic (const Surface & s2, int & inv, double eps) const
  {
    const Sphere * sp2 = dynamic_cast<const Sphere*>  (&s2);

    if (!sp2) return 0;

    if (Dist (sp2->c, c) > eps) return 0;
    if (fabs (sp2->r - r) > eps) return 0;

    inv = 0;

    return 1;
  }


  void Sphere :: DefineTangentialPlane (const Point<3> & ap1, const Point<3> & ap2)
  {
    Surface::DefineTangentialPlane (ap1, ap2);

    ez = p1 - c;
    ez /= ez.Length();

    ex = p2 - p1;
    ex -= (ex * ez) * ez;
    ex /= ex.Length();

    ey = Cross (ez, ex);
  }


  void Sphere :: ToPlane (const Point<3> & p, Point<2> & pplane, double h, int & zone) const
  {
    Vec<3> p1p;
  
    p1p = p - p1;
  
    /*
      if (p1p * ez < -r)
      {
      zone = -1;
      pplane = Point<2> (1E8, 1E8);
      }
      else
      { 
      zone = 0;
      p1p /= h;
      pplane(0) = p1p * ex;
      pplane(1) = p1p * ey;
      }
    */

    Point<3> p1top = c + (c - p1);

    Vec<3> p1topp = p - p1top;
    Vec<3> p1topp1 = p1 - p1top;
    Vec<3> lam;
    //  SolveLinearSystem (ex, ey, p1topp, p1topp1, lam);

    Mat<3> m;
    for (int i = 0; i < 3; i++)
      {
        m(i, 0) = ex(i);
        m(i, 1) = ey(i);
        m(i, 2) = p1topp(i);
      }
    m.Solve (p1topp1, lam);

    pplane(0) = -lam(0) / h;
    pplane(1) = -lam(1) / h;
  
    if (lam(2) > 2)
      zone = -1;
    else 
      zone = 0;
  }

  void Sphere :: FromPlane (const Point<2> & pplane, Point<3> & p, double h) const
  {
    /*
    //  Vec<3> p1p;
    double z;
    Point<2> pplane2 (pplane);

    pplane2(0) *= h;
    pplane2(1) *= h;
    z = -r + sqrt (sqr (r) - sqr (pplane2(0)) - sqr (pplane2(1)));
    //  p = p1;
    p(0) = p1(0) + pplane2(0) * ex(0) + pplane2(1) * ey(0) + z * ez(0);
    p(1) = p1(1) + pplane2(0) * ex(1) + pplane2(1) * ey(1) + z * ez(1);
    p(2) = p1(2) + pplane2(0) * ex(2) + pplane2(1) * ey(2) + z * ez(2);
    */

    Point<2> pplane2 (pplane);

    pplane2(0) *= h;
    pplane2(1) *= h;

    p(0) = p1(0) + pplane2(0) * ex(0) + pplane2(1) * ey(0);
    p(1) = p1(1) + pplane2(0) * ex(1) + pplane2(1) * ey(1);
    p(2) = p1(2) + pplane2(0) * ex(2) + pplane2(1) * ey(2);
    Project (p);
  }


  void Sphere :: Project (Point<3> & p) const
  {
    Vec<3> v;
    v = p - c;
    v *= (r / v.Length());
    p = c + v;
  }


  INSOLID_TYPE Sphere :: BoxInSolid (const BoxSphere<3> & box) const
  {
    double dist;
    dist = Dist (box.Center(), c);

    if (dist - box.Diam()/2 > r) return IS_OUTSIDE;
    if (dist + box.Diam()/2 < r) return IS_INSIDE;
    return DOES_INTERSECT;
  }

  double Sphere :: HesseNorm () const
  {
    return 2 / r;
  }


  Point<3> Sphere :: GetSurfacePoint () const
  {
    return c + Vec<3> (r, 0, 0);
  }


  void Sphere :: GetTriangleApproximation 
  (TriangleApproximation & tas, 
   const Box<3> & /* boundingbox */, double facets) const
  {
    int n = int(facets) + 1;  

    for (int j = 0; j <= n; j++)
      for (int i = 0; i <= n; i++)
        {
          double lg = 2 * M_PI * double (i) / n;
          double bg = M_PI * (double(j) / n - 0.5);

          Point<3> p(c(0) + r * cos(bg) * sin (lg),
                     c(1) + r * cos(bg) * cos (lg),
                     c(2) + r * sin(bg));
          tas.AddPoint (p);
        }

    for (int j = 0; j < n; j++)
      for (int i = 0; i < n; i++)
        {
          int pi = i + (n+1) * j;
          tas.AddTriangle (TATriangle (0, pi, pi+1, pi+n+2));
          tas.AddTriangle (TATriangle (0, pi, pi+n+2, pi+n+1));
        }
  }





  Ellipsoid :: 
  Ellipsoid (const Point<3> & aa,
             const Vec<3> & av1, const Vec<3> & av2, const Vec<3> & av3)
  {
    a = aa;
    v1 = av1;
    v2 = av2;
    v3 = av3;

    CalcData();
  }


  void Ellipsoid :: CalcData ()
  {
    // f = (x-a, vl)^2 / |vl|^2 + (x-a, vs)^2 / |vs|^2 -1
    // f = sum_{i=1}^3  (x-a,v_i)^2 / |vi|^4 - 1   =  sum (x-a,hv_i)^2
  
    Vec<3> hv1, hv2, hv3;
    double lv1 = v1.Length2 ();
    if (lv1 < 1e-32) lv1 = 1;
    double lv2 = v2.Length2 ();
    if (lv2 < 1e-32) lv2 = 1;
    double lv3 = v3.Length2 ();
    if (lv3 < 1e-32) lv3 = 1;

    rmin = sqrt (min3 (lv1, lv2, lv3));

    hv1 = (1.0 / lv1) * v1;
    hv2 = (1.0 / lv2) * v2;
    hv3 = (1.0 / lv3) * v3;

    cxx = hv1(0) * hv1(0) + hv2(0) * hv2(0) + hv3(0) * hv3(0);
    cyy = hv1(1) * hv1(1) + hv2(1) * hv2(1) + hv3(1) * hv3(1);
    czz = hv1(2) * hv1(2) + hv2(2) * hv2(2) + hv3(2) * hv3(2);

    cxy = 2 * (hv1(0) * hv1(1) + hv2(0) * hv2(1) + hv3(0) * hv3(1));
    cxz = 2 * (hv1(0) * hv1(2) + hv2(0) * hv2(2) + hv3(0) * hv3(2));
    cyz = 2 * (hv1(1) * hv1(2) + hv2(1) * hv2(2) + hv3(1) * hv3(2));

    Vec<3> va (a);
    c1 = sqr(va * hv1) + sqr(va * hv2) + sqr(va * hv3) - 1;
  
    Vec<3> v = -2 * (va * hv1) * hv1 - 2 * (va * hv2) * hv2  - 2 * (va * hv3) * hv3;
    cx = v(0);
    cy = v(1);
    cz = v(2);
  }


  INSOLID_TYPE Ellipsoid :: BoxInSolid (const BoxSphere<3> & box) const
  {
    // double grad = 2.0 / rmin;
    // double grad = 3*(box.Center()-a).Length() / (rmin*rmin*rmin);

    double ggrad = 1.0 / (rmin*rmin);
    Vec<3> g;
    double val = CalcFunctionValue (box.Center());
    CalcGradient (box.Center(), g);
    double grad = g.Length();

    double r = box.Diam() / 2;
    double maxval = grad * r + ggrad * r * r;

    //  (*testout) << "box = " << box << ", val = " << val << ", maxval = " << maxval << endl;

    if (val > maxval) return IS_OUTSIDE;
    if (val < -maxval) return IS_INSIDE;
    return DOES_INTERSECT;
  }


  double Ellipsoid :: HesseNorm () const
  {
    return 1.0/ (rmin * rmin);
  }

  double Ellipsoid :: MaxCurvature () const
  {
    const double a2 = v1.Length2();
    const double b2 = v2.Length2();
    const double c2 = v3.Length2();

    return max3 ( sqrt(a2)/min2(b2,c2), sqrt(b2)/min2(a2,c2), sqrt(c2)/min2(a2,b2) );
  }

  Point<3> Ellipsoid :: GetSurfacePoint () const
  {
    return a + v1;
  }



  void Ellipsoid :: GetTriangleApproximation 
  (TriangleApproximation & tas, 
   const Box<3> & /* boundingbox */, double facets) const
  {
    int n = int(facets) + 1;  

    for (int j = 0; j <= n; j++)
      for (int i = 0; i <= n; i++)
        {
          double lg = 2 * M_PI * double (i) / n;
          double bg = M_PI * (double(j) / n - 0.5);

          Point<3> p(a + 
                     sin (bg) * v1 + 
                     cos (bg) * sin (lg) * v2 +
                     cos (bg) * cos (lg) * v3);

          tas.AddPoint (p);
        }

    for (int j = 0; j < n; j++)
      for (int i = 0; i < n; i++)
        {
          int pi = i + (n+1) * j;
          tas.AddTriangle (TATriangle (0, pi, pi+1, pi+n+2));
          tas.AddTriangle (TATriangle (0, pi, pi+n+2, pi+n+1));
        }
  }

















  Cylinder :: Cylinder (Array<double> & coeffs)
  {
    SetPrimitiveData(coeffs);
  }

  Cylinder :: Cylinder (const Point<3> & aa, const Point<3> & ab, double ar)
  {
    a = aa;
    b = ab;
    vab = (b - a);
    vab /= vab.Length();
    r = ar;

    // ( <x,x> - 2 <x,a> + <a,a>
    //   - <x,vab>^2 + 2 <x,vab> <a, vab> - <a, vab>^2
    //   - r^2) / (2r) = 0

    double hv;
    cxx = cyy = czz = 0.5 / r;
    cxy = cxz = cyz = 0;
    cx = - a(0) / r;
    cy = - a(1) / r;
    cz = - a(2) / r;
    c1 = (a(0) * a(0) + a(1) * a(1) + a(2) * a(2)) / (2 * r);
    hv = a(0) * vab(0) + a(1) * vab(1) + a(2) * vab(2);
    cxx -= vab(0) * vab(0) / (2 * r);
    cyy -= vab(1) * vab(1) / (2 * r);
    czz -= vab(2) * vab(2) / (2 * r);
    cxy -= vab(0) * vab(1) / r;
    cxz -= vab(0) * vab(2) / r;
    cyz -= vab(1) * vab(2) / r;
    cx += vab(0) * hv / r;
    cy += vab(1) * hv / r;
    cz += vab(2) * hv / r;
    c1 -= hv * hv / (2 * r);
    c1 -= r / 2;
    //  PrintCoeff ();
  }




  void Cylinder :: GetPrimitiveData (const char *& classname, Array<double> & coeffs) const
  {
    classname = "cylinder";
    coeffs.SetSize (7);
    coeffs.Elem(1) = a(0);
    coeffs.Elem(2) = a(1);
    coeffs.Elem(3) = a(2);
    coeffs.Elem(4) = b(0);
    coeffs.Elem(5) = b(1);
    coeffs.Elem(6) = b(2);
    coeffs.Elem(7) = r;
  }

  void Cylinder :: SetPrimitiveData (Array<double> & coeffs)
  {
    a(0) = coeffs.Elem(1);
    a(1) = coeffs.Elem(2);
    a(2) = coeffs.Elem(3);
    b(0) = coeffs.Elem(4);
    b(1) = coeffs.Elem(5);
    b(2) = coeffs.Elem(6);
    r = coeffs.Elem(7);


    vab = (b - a);
    vab /= vab.Length();


    double hv;
    cxx = cyy = czz = 0.5 / r;
    cxy = cxz = cyz = 0;
    cx = - a(0) / r;
    cy = - a(1) / r;
    cz = - a(2) / r;
    c1 = (a(0) * a(0) + a(1) * a(1) + a(2) * a(2)) / (2 * r);
    hv = a(0) * vab(0) + a(1) * vab(1) + a(2) * vab(2);
    cxx -= vab(0) * vab(0) / (2 * r);
    cyy -= vab(1) * vab(1) / (2 * r);
    czz -= vab(2) * vab(2) / (2 * r);
    cxy -= vab(0) * vab(1) / r;
    cxz -= vab(0) * vab(2) / r;
    cyz -= vab(1) * vab(2) / r;
    cx += vab(0) * hv / r;
    cy += vab(1) * hv / r;
    cz += vab(2) * hv / r;
    c1 -= hv * hv / (2 * r);
    c1 -= r / 2;
  }

  Primitive * Cylinder :: CreateDefault ()
  {
    return new Cylinder (Point<3> (0,0,0), Point<3> (1,0,0), 1);
  }




  Primitive * Cylinder :: Copy () const
  {
    return new Cylinder (a, b, r);
  }


  int Cylinder :: IsIdentic (const Surface & s2, int & inv, double eps) const
  {
    const Cylinder * cyl2 = dynamic_cast<const Cylinder*>  (&s2);

    if (!cyl2) return 0;

    if (fabs (cyl2->r - r) > eps) return 0;

    Vec<3> v1 = b - a;
    Vec<3> v2 = cyl2->a - a;

    if ( fabs (v1 * v2) < (1-eps) * v1.Length() * v2.Length()) return 0;
    v2 = cyl2->b - a;
    if ( fabs (v1 * v2) < (1-eps) * v1.Length() * v2.Length()) return 0;

    inv = 0;
    return 1;
  }



  void Cylinder :: Transform (Transformation<3> & trans)
  {
    Point<3> hp;
    trans.Transform (a, hp);
    a = hp;
    trans.Transform (b, hp);
    b = hp;

    vab = (b - a);
    vab /= vab.Length();

    // ( <x,x> - 2 <x,a> + <a,a>
    //   - <x,vab>^2 + 2 <x,vab> <a, vab> - <a, vab>^2
    //   - r^2) / (2r) = 0

    double hv;
    cxx = cyy = czz = 0.5 / r;
    cxy = cxz = cyz = 0;
    cx = - a(0) / r;
    cy = - a(1) / r;
    cz = - a(2) / r;
    c1 = (a(0) * a(0) + a(1) * a(1) + a(2) * a(2)) / (2 * r);
    hv = a(0) * vab(0) + a(1) * vab(1) + a(2) * vab(2);
    cxx -= vab(0) * vab(0) / (2 * r);
    cyy -= vab(1) * vab(1) / (2 * r);
    czz -= vab(2) * vab(2) / (2 * r);
    cxy -= vab(0) * vab(1) / r;
    cxz -= vab(0) * vab(2) / r;
    cyz -= vab(1) * vab(2) / r;
    cx += vab(0) * hv / r;
    cy += vab(1) * hv / r;
    cz += vab(2) * hv / r;
    c1 -= hv * hv / (2 * r);
    c1 -= r / 2;
    //  PrintCoeff ();
  }









  void Cylinder :: DefineTangentialPlane (const Point<3> & ap1, const Point<3> & ap2)
  {
    Surface::DefineTangentialPlane (ap1, ap2);

    ez = Center (p1, p2) - a;
    ez -= (ez * vab) * vab;
    ez /= ez.Length();

    ex = p2 - p1;
    ex -= (ex * ez) * ez;
    ex /= ex.Length();

    ey = Cross (ez, ex);
  }


  void Cylinder :: ToPlane (const Point<3> & p, 
                            Point<2> & pplane, 
                            double h, int & zone) const
  {
    Point<3> cp1p2 = Center (p1, p2);
    Project (cp1p2);
  
    Point<3> ccp1p2 = a + ( (cp1p2 - a) * vab ) * vab;

    Vec<3> er = cp1p2 - ccp1p2;
    er.Normalize();
    Vec<3> ephi = Cross (vab, er);

    double co, si;
    Point<2> p1p, p2p, pp;

    co = er * (p1 - ccp1p2);
    si = ephi * (p1 - ccp1p2);
    p1p(0) = r * atan2 (si, co);
    p1p(1) = vab * (p1 - ccp1p2);

    co = er * (p2 - ccp1p2);
    si = ephi * (p2 - ccp1p2);
    p2p(0) = r * atan2 (si, co);
    p2p(1) = vab * (p2 - ccp1p2);
  
    co = er * (p - ccp1p2);
    si = ephi * (p - ccp1p2);

    double phi = atan2 (si, co);
    pp(0) = r * phi;
    pp(1) = vab * (p - ccp1p2);
  
    zone = 0;
    if (phi > 1.57) zone = 1;
    if (phi < -1.57) zone = 2;



    Vec<2> e2x = p2p - p1p;
    e2x /= e2x.Length();

    Vec<2> e2y (-e2x(1), e2x(0));

    Vec<2> p1pp = pp - p1p;


    pplane(0) = (p1pp * e2x) / h;
    pplane(1) = (p1pp * e2y) / h;

    /*
      (*testout) << "p1 = " << p1 << ",  p2 = " << p2 << endl;
      (*testout) << "p = " << p << ",  pp = " << pp << ",  pplane = " << pplane << endl;
    */

    /*
      Vec<3> p1p;

      p1p = p - p1;

      if (p1p * ez < -1 * r)
      {
      zone = -1;
      pplane(0) = 1e8;
      pplane(1) = 1e8;
      }
      else
      {
      zone = 0;
      p1p /= h;
      pplane(0) = p1p * ex;
      pplane(1) = p1p * ey;
      }
    */
  }

  void Cylinder :: FromPlane (const Point<2> & pplane, Point<3> & p, double h) const
  {
    Point<2> pplane2 (pplane);

    pplane2(0) *= h;
    pplane2(1) *= h;

    p(0) = p1(0) + pplane2(0) * ex(0) + pplane2(1) * ey(0);
    p(1) = p1(1) + pplane2(0) * ex(1) + pplane2(1) * ey(1);
    p(2) = p1(2) + pplane2(0) * ex(2) + pplane2(1) * ey(2);
    Project (p);
  }


  void Cylinder :: Project (Point<3> & p) const
  {
    Vec<3> v;
    Point<3> c;

    c = a + ((p - a) * vab) * vab;
    v = p - c;
    v *= (r / v.Length());
    p = c + v;
  }
  /*
    int Cylinder :: RootInBox (const BoxSphere<3> & box) const
    {
    double dist;
    dist = sqrt (2 * CalcFunctionValue(box.Center()) * r + r * r);
    if (fabs (dist - r) > box.Diam()/2) return 0;
    return 2;
    }
  */

  INSOLID_TYPE Cylinder :: BoxInSolid (const BoxSphere<3> & box) const
  {
    double dist;
    //  dist = sqrt (2 * CalcFunctionValue(box.Center()) * r + r * r);

    dist =  (2 * CalcFunctionValue(box.Center()) * r + r * r);
    if (dist <= 0) dist = 0;
    else dist = sqrt (dist + 1e-16);

    if (dist - box.Diam()/2 > r) return IS_OUTSIDE;
    if (dist + box.Diam()/2 < r) return IS_INSIDE;
    return DOES_INTERSECT;
  }


  double Cylinder :: HesseNorm () const
  {
    return 2 / r;
  }

  Point<3> Cylinder :: GetSurfacePoint () const
  {
    Vec<3> vr;
    if (fabs (vab(0)) > fabs(vab(2)))
      vr = Vec<3> (vab(1), -vab(0), 0);
    else
      vr = Vec<3> (0, -vab(2), vab(1));
    
    vr *= (r / vr.Length());
    return a + vr;
  }

  void Cylinder :: GetTriangleApproximation 
  (TriangleApproximation & tas, 
   const Box<3> & /* boundingbox */, double facets) const
  {
    int n = int(facets) + 1;  

    Vec<3> lvab = b - a;
    Vec<3> n1 = lvab.GetNormal();
    Vec<3> n2 = Cross (lvab, n1);
  
    n1.Normalize();
    n2.Normalize();


    for (int j = 0; j <= n; j++)
      for (int i = 0; i <= n; i++)
        {
          double lg = 2 * M_PI * double (i) / n;
          double bg = double(j) / n;

          Point<3> p = a + (bg * lvab) 
            + ((r * cos(lg)) * n1) 
            + ((r * sin(lg)) * n2);

          tas.AddPoint (p);
        }

    for (int j = 0; j < n; j++)
      for (int i = 0; i < n; i++)
        {
          int pi = i + (n+1) * j;
          tas.AddTriangle (TATriangle (0, pi, pi+1, pi+n+2));
          tas.AddTriangle (TATriangle (0, pi, pi+n+2, pi+n+1));
        }
  }









  EllipticCylinder :: 
  EllipticCylinder (const Point<3> & aa,
                    const Vec<3> & avl, const Vec<3> & avs)
  {
    a = aa;
    if(avl.Length2() > avs.Length2())
      {
        vl = avl;
        vs = avs;
      }
    else
      {
        vl = avs;
        vs = avl;
      }

    CalcData();
    // Print (cout);
  }


  void EllipticCylinder :: CalcData ()
  {
    // f = (x-a, vl)^2 / |vl|^2 + (x-a, vs)^2 / |vs|^2 -1

    Vec<3> hvl, hvs;
    double lvl = vl.Length2 ();
    if (lvl < 1e-32) lvl = 1;
    double lvs = vs.Length2 ();
    if (lvs < 1e-32) lvs = 1;

    hvl = (1.0 / lvl) * vl;
    hvs = (1.0 / lvs) * vs;

    cxx = hvl(0) * hvl(0) + hvs(0) * hvs(0);
    cyy = hvl(1) * hvl(1) + hvs(1) * hvs(1);
    czz = hvl(2) * hvl(2) + hvs(2) * hvs(2);

    cxy = 2 * (hvl(0) * hvl(1) + hvs(0) * hvs(1));
    cxz = 2 * (hvl(0) * hvl(2) + hvs(0) * hvs(2));
    cyz = 2 * (hvl(1) * hvl(2) + hvs(1) * hvs(2));

    Vec<3> va (a);
    c1 = pow(va * hvl,2) + pow(va * hvs,2) - 1;
  
    Vec<3> v = -2 * (va * hvl) * hvl - 2 * (va * hvs) * hvs;
    cx = v(0);
    cy = v(1);
    cz = v(2);
  }


  INSOLID_TYPE EllipticCylinder :: BoxInSolid (const BoxSphere<3> & box) const
  {
    double grad = 2.0 / vs.Length ();
    double ggrad = 1.0 / vs.Length2 ();

    double val = CalcFunctionValue (box.Center());
    double r = box.Diam() / 2;
    double maxval = grad * r + ggrad * r * r;

    // (*testout) << "box = " << box << ", val = " << val << ", maxval = " << maxval << endl;

    if (val > maxval) return IS_OUTSIDE;
    if (val < -maxval) return IS_INSIDE;
    return DOES_INTERSECT;
  }


  double EllipticCylinder :: HesseNorm () const
  {
    return 1.0/min(vs.Length2 (),vl.Length2());
  }

  double EllipticCylinder :: MaxCurvature () const
  {
    double aa = vs.Length();
    double bb = vl.Length();

    return max2(bb/(aa*aa),aa/(bb*bb));
  }

  double EllipticCylinder :: MaxCurvatureLoc (const Point<3> & /* c */, 
                                              double /* rad */) const
  {
    // saubere Loesung wird noch notwendig !!!
    double aa = vs.Length();
    double bb = vl.Length();
    return max2(bb/(aa*aa),aa/(bb*bb));
  }



  Point<3> EllipticCylinder :: GetSurfacePoint () const
  {
    return a + vl;
  }



  void EllipticCylinder :: GetTriangleApproximation 
  (TriangleApproximation & tas, 
   const Box<3> & /* boundingbox */, double facets) const
  {
    int n = int(facets) + 1;  

    Vec<3> axis = Cross (vl, vs);

    for (int j = 0; j <= n; j++)
      for (int i = 0; i <= n; i++)
        {
          double lg = 2 * M_PI * double (i) / n;
          double bg = double(j) / n;

          Point<3> p = a + (bg * axis)
            + cos(lg) * vl + sin(lg) * vs;

          tas.AddPoint (p);
        }

    for (int j = 0; j < n; j++)
      for (int i = 0; i < n; i++)
        {
          int pi = i + (n+1) * j;
          tas.AddTriangle (TATriangle (0, pi, pi+1, pi+n+2));
          tas.AddTriangle (TATriangle (0, pi, pi+n+2, pi+n+1));
        }
  }










  Cone :: Cone (const Point<3> & aa, const Point<3> & ab, 
                double ara, double arb)
  {
    a = aa;
    b = ab;
    ra = ara;
    rb = arb;

    CalcData();
    // Print (cout);
  }


  Primitive * Cone :: CreateDefault ()
  {
    return new Cone (Point<3> (0,0,0), Point<3> (1,0,0), 0.5, 0.2);
  }




  void Cone :: GetPrimitiveData (const char *& classname, Array<double> & coeffs) const
  {
    classname = "cone";
    coeffs.SetSize (8);
    coeffs.Elem(1) = a(0);
    coeffs.Elem(2) = a(1);
    coeffs.Elem(3) = a(2);
    coeffs.Elem(4) = b(0);
    coeffs.Elem(5) = b(1);
    coeffs.Elem(6) = b(2);
    coeffs.Elem(7) = ra;
    coeffs.Elem(8) = rb;
  }

  void Cone :: SetPrimitiveData (Array<double> & coeffs)
  {
    a(0) = coeffs.Elem(1);
    a(1) = coeffs.Elem(2);
    a(2) = coeffs.Elem(3);
    b(0) = coeffs.Elem(4);
    b(1) = coeffs.Elem(5);
    b(2) = coeffs.Elem(6);
    ra = coeffs.Elem(7);
    rb = coeffs.Elem(8);

    CalcData();
  }

  void Cone :: CalcData ()
  {

    minr = (ra < rb) ? ra : rb;

    vab = b - a;
    vabl = vab.Length();

    Vec<3> va (a);

    //
    //   f = r(P)^2 - R(z(P))^2
    //
    //   z(P) = t0vec * P + t0 = (P-a, b-a)/(b-a,b-a)
    //   R(z(P)) = t1vec * P + t1 = rb * z + ra * (1-z)
    //   r(P)^2 =||P-a||^2 - ||a-b||^2 z^2k


    t0vec = vab;
    t0vec /= (vabl * vabl);
    t0 = -(va * vab) / (vabl * vabl);

    t1vec = t0vec;
    t1vec *= (rb - ra);
    t1 = ra + (rb - ra) * t0; 

    cxx = cyy = czz = 1;
    cxy = cxz = cyz = 0;

    cxx = 1 - (vab*vab) * t0vec(0) * t0vec(0) - t1vec(0) * t1vec(0);
    cyy = 1 - (vab*vab) * t0vec(1) * t0vec(1) - t1vec(1) * t1vec(1);
    czz = 1 - (vab*vab) * t0vec(2) * t0vec(2) - t1vec(2) * t1vec(2);
  
    cxy = -2 * (vab * vab) * t0vec(0) * t0vec(1) - 2 * t1vec(0) * t1vec(1);
    cxz = -2 * (vab * vab) * t0vec(0) * t0vec(2) - 2 * t1vec(0) * t1vec(2);
    cyz = -2 * (vab * vab) * t0vec(1) * t0vec(2) - 2 * t1vec(1) * t1vec(2);

    cx = -2 * a(0) - 2 * (vab * vab) * t0 * t0vec(0) - 2 * t1 * t1vec(0);
    cy = -2 * a(1) - 2 * (vab * vab) * t0 * t0vec(1) - 2 * t1 * t1vec(1);
    cz = -2 * a(2) - 2 * (vab * vab) * t0 * t0vec(2) - 2 * t1 * t1vec(2);

    c1 = va.Length2() - (vab * vab) * t0 * t0 - t1 * t1;


    double maxr = max2(ra,rb);
    cxx /= maxr; cyy /= maxr; czz /= maxr;
    cxy /= maxr; cxz /= maxr; cyz /= maxr;
    cx /= maxr; cy /= maxr; cz /= maxr;
    c1 /= maxr;


    // (*testout) << "t0vec = " << t0vec << " t0 = " << t0 << endl;
    // (*testout) << "t1vec = " << t1vec << " t1 = " << t1 << endl;
    // PrintCoeff (*testout);
  }


  INSOLID_TYPE Cone :: BoxInSolid (const BoxSphere<3> & box) const
  {
    double rp, dist;

    Vec<3> cv(box.Center());

    rp = cv * t1vec + t1;
    dist = sqrt (CalcFunctionValue(box.Center()) *max2(ra,rb) + rp * rp) - rp;

    if (dist - box.Diam() > 0) return IS_OUTSIDE;
    if (dist + box.Diam() < 0) return IS_INSIDE;
    return DOES_INTERSECT;
  }


  double Cone :: HesseNorm () const
  {
    return 2 / minr;
  }


  double Cone ::  LocH (const Point<3> & p, double /* x */, 
                        double /* c */, double hmax) const
  {
    //double bloch = Surface::LocH (p, x, c, hmax);
    Vec<3> g;
    CalcGradient (p, g);

    double lam = Abs(g);
    double meancurv = 
      -( 2  * g(0)*g(1)*cxy - 2 * czz * (g(0)*g(0)+g(1)*g(1))
         +2 * g(1)*g(2)*cyz - 2 * cxx * (g(1)*g(1)+g(2)*g(2))
         +2 * g(0)*g(2)*cxz - 2 * cyy * (g(0)*g(0)+g(2)*g(2))) / (3*lam*lam*lam);

    // cout << "type = " << typeid(*this).name() << ", baseh = " << bloch << ", meancurv = " << meancurv << endl;
    // return bloch;
  
    meancurv = fabs (meancurv);
    if (meancurv < 1e-20) meancurv = 1e-20;

    // cout << "c = " << c << ", safety = " << mparam.curvaturesafety << endl;
    double hcurv = 1.0/(4*meancurv*mparam.curvaturesafety);

    return min2 (hmax, hcurv);
  }


  Point<3> Cone :: GetSurfacePoint () const
  {
    Vec<3> vr = vab.GetNormal ();
  
    vr *= (ra / vr.Length());
    return a + vr;
  }





  void Cone :: GetTriangleApproximation 
  (TriangleApproximation & tas, 
   const Box<3> & /* boundingbox */, double facets) const
  {
    int i, j;
    double lg, bg;
    int n = int(facets) + 1;  

    Vec<3> lvab = b - a;
    Vec<3> n1 = lvab.GetNormal();
    Vec<3> n2 = Cross (lvab, n1);
  
    n1.Normalize();
    n2.Normalize();


    for (j = 0; j <= n; j++)
      for (i = 0; i <= n; i++)
        {
          lg = 2 * M_PI * double (i) / n;
          bg = double(j) / n;

          Point<3> p = a + (bg * lvab) 
            + (( (ra+(rb-ra)*bg)  * cos(lg)) * n1) 
            + (( (ra+(rb-ra)*bg)  * sin(lg)) * n2);

          tas.AddPoint (p);
        }

    for (j = 0; j < n; j++)
      for (i = 0; i < n; i++)
        {
          int pi = i + (n+1) * j;
          tas.AddTriangle (TATriangle (0, pi, pi+1, pi+n+2));
          tas.AddTriangle (TATriangle (0, pi, pi+n+2, pi+n+1));
        }
  }









  /// Torus 
  /// Lorenzo Codecasa (codecasa@elet.polimi.it)
  /// April 27th, 2005 
  ///
  /// begin...
  Torus :: Torus (const Point<3> & ac, const Vec<3> & an, double aR, double ar)
  {
    c = ac;
    n = an;
    R = aR;
    r = ar;
  }

  void Torus :: GetPrimitiveData (const char *& classname, Array<double> & coeffs) const
  {
    classname = "torus";
    coeffs.SetSize (8);
    coeffs.Elem(1) = c(0);
    coeffs.Elem(2) = c(1);
    coeffs.Elem(3) = c(2);
    coeffs.Elem(4) = n(0);
    coeffs.Elem(5) = n(1);
    coeffs.Elem(6) = n(2);
    coeffs.Elem(7) = R;
    coeffs.Elem(8) = r;
  }

  void Torus :: SetPrimitiveData (Array<double> & coeffs)
  {
    c(0) = coeffs.Elem(1);
    c(1) = coeffs.Elem(2);
    c(2) = coeffs.Elem(3);
    n(0) = coeffs.Elem(4);
    n(1) = coeffs.Elem(5);
    n(2) = coeffs.Elem(6);
    R = coeffs.Elem(7);
    r = coeffs.Elem(8);
  }

  Primitive * Torus :: CreateDefault ()
  {
    return new Torus (Point<3> (0,0,0), Vec<3> (0,0,1), 2, 1);
  }

  Primitive * Torus :: Copy () const
  {
    return new Torus (c, n, R, r);
  }

  void Torus :: Transform (Transformation<3> & trans)
  {
    Point<3> hc;
    trans.Transform (c, hc);
    c = hc;
  
    Vec<3> hn;
    trans.Transform (n, hn);
    n = hn;
  }

  int Torus :: IsIdentic (const Surface & s2, int & inv, double eps) const
  {
    const Torus * torus2 = dynamic_cast<const Torus*>  (&s2);

    if (!torus2) return 0;

    if (fabs (torus2->R - R) > eps) return 0;
  
    if (fabs (torus2->r - r) > eps) return 0;

    Vec<3> v2 = torus2->n - n;
    if ( v2 * v2 > eps ) return 0;
  
    v2 = torus2->c - c;
    if ( v2 * v2 > eps ) return 0;

    inv = 0;
    return 1;
  }

  double Torus :: CalcFunctionValue (const Point<3> & point) const
  {
    Vec<3> v1 = point - c;
    double a1 = v1(0) * v1(0) + v1(1) * v1(1) + v1(2) * v1(2);
    double a2 = n(0) * v1(0) + n(1) * v1(1) + n(2) * v1(2);
    double a3 = a1 + R * R - r * r;
    double a4 = n(0) * n(0) + n(1) * n(1) + n(2) * n(2);
    return ( a3 * a3 -4 * R * R * ( a1 - a2 * a2 / a4 ) ) / ( R * R * R );
  }

  void Torus :: CalcGradient (const Point<3> & point, Vec<3> & grad) const
  {
    Vec<3> v1 = point - c;
    double a1 = v1(0) * v1(0) + v1(1) * v1(1) + v1(2) * v1(2);
    double a2 = n(0) * v1(0) + n(1) * v1(1) + n(2) * v1(2);
    double a3 = a1 - R * R - r * r;
    double a4 = n(0) * n(0) + n(1) * n(1) + n(2) * n(2);
    grad(0) = ( 4 * a3 * v1(0) + 8 * R * R * a2 / a4 * n(0) ) / ( R * R * R );
    grad(1) = ( 4 * a3 * v1(1) + 8 * R * R * a2 / a4 * n(1) ) / ( R * R * R );
    grad(2) = ( 4 * a3 * v1(2) + 8 * R * R * a2 / a4 * n(2) ) / ( R * R * R );
  }

  void Torus :: CalcHesse (const Point<3> & point, Mat<3> & hesse) const
  {
    Vec<3> v1 = point - c;
    double a1 = v1(0) * v1(0) + v1(1) * v1(1) + v1(2) * v1(2);
    double a3 = a1 - R * R - r * r;
    double a4 = n(0) * n(0) + n(1) * n(1) + n(2) * n(2);
    hesse(0,0) = ( 4 * a3 + 8 * (v1(0) * v1(0) + (R * n(0)) * (R * n(0)) / a4 ) ) / ( R * R * R );
    hesse(1,1) = ( 4 * a3 + 8 * (v1(1) * v1(1) + (R * n(1)) * (R * n(1)) / a4 ) ) / ( R * R * R );
    hesse(2,2) = ( 4 * a3 + 8 * (v1(2) * v1(2) + (R * n(2)) * (R * n(2)) / a4 ) ) / ( R * R * R );
    hesse(0,1) = hesse(1,0) = 8 * (v1(0) * v1(1) + (R * n(0)) * (R * n(1)) / a4 ) / ( R * R * R );
    hesse(1,2) = hesse(2,1) = 8 * (v1(1) * v1(2) + (R * n(1)) * (R * n(2)) / a4) / ( R * R * R );
    hesse(0,2) = hesse(2,0) = 8 * (v1(0) * v1(2) + (R * n(0)) * (R * n(2)) / a4) / ( R * R * R );
  }

  double Torus :: HesseNorm () const
  {	
    return  ( 2 / r + 2 / ( R - r ) );
  }

  Point<3> Torus :: GetSurfacePoint () const
  {
    Vec<3> vn = n.GetNormal();
    return c + ( R + r ) * vn.Normalize();
  }

  /// void Torus :: DefineTangentialPlane (const Point<3> & ap1, const Point<3> & ap2)
  /// {
  /// }

  /// void Torus :: ToPlane (const Point<3> & p, 
  ///			  Point<2> & pplane, 
  ///			  double h, int & zone) const
  /// {
  /// }

  /// void Torus :: FromPlane (const Point<2> & pplane, Point<3> & p, double h) const
  /// {
  /// }

  /// void Torus :: Project (Point<3> & p) const
  /// {
  /// }

  INSOLID_TYPE Torus :: BoxInSolid (const BoxSphere<3> & box) const
  {
    Vec<3> v1 = box.Center() - c;
    double a1 = v1(0) * v1(0) + v1(1) * v1(1) + v1(2) * v1(2);
    double a2 = n(0) * v1(0) + n(1) * v1(1) + n(2) * v1(2);
    double a4 = n(0) * n(0) + n(1) * n(1) + n(2) * n(2);
 
    double dist = sqrt( a1 + R * R - 2 * R * sqrt( a1 - a2 * a2 / a4) );

    if (dist - box.Diam()/2 > r) return IS_OUTSIDE;
    if (dist + box.Diam()/2 < r) return IS_INSIDE;
    return DOES_INTERSECT;
  }

  void Torus :: GetTriangleApproximation (TriangleApproximation & tas, 
                                          const Box<3> & /* boundingbox */, double facets) const
  {
    int N = int(facets) + 1;  

    Vec<3> lvab = n ;
    lvab.Normalize();
  
    Vec<3> n1 = lvab.GetNormal();
    n1.Normalize();
  
    Vec<3> n2 = Cross(lvab, n1);
    n2.Normalize();
  
    for (int j = 0; j <= N; j++)
      for (int i = 0; i <= N; i++)
	{
          double lg = 2 * M_PI * double (i) / N;
          double bg = 2 * M_PI * double(j) / N;
	
          Point<3> p = c + ( R + r * cos(lg) ) * ( cos(bg) * n1 + sin(bg) * n2 ) + r * sin(lg) * n;
          tas.AddPoint (p);
	}
	
    for (int j = 0; j < N; j++)
      for (int i = 0; i < N; i++)
	{
          int pi = i + (N+1) * j;
          tas.AddTriangle (TATriangle (0, pi, pi+1, pi+N+2));
          tas.AddTriangle (TATriangle (0, pi, pi+N+2, pi+N+1));
	}
  } 
  
  void Torus :: Read (istream & ist)
  {
    ist >> c(0) >> c(1) >> c(2) >> n(0) >> n(1) >> n(2) >> R >> r;
  }

  void Torus :: Print (ostream & ost) const
  {
    ost << c(0) << "  " << c(1) << "  " << c(2) << "  "
        << n(0) << "  " << n(1) << "  " << n(2) << "  "
        << R    << "  " << r    << endl;
  }

  /// end...
















}