netgen/libsrc/csg/extrusion.cpp

#include <mystdlib.h>

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


namespace netgen
{

  void ExtrusionFace :: Init(void)
  {
    p0.SetSize(path->GetNSplines());
    x_dir.SetSize(path->GetNSplines());
    y_dir.SetSize(path->GetNSplines());
    z_dir.SetSize(path->GetNSplines());
    loc_z_dir.SetSize(path->GetNSplines());
    spline3_path.SetSize(path->GetNSplines());
    line_path.SetSize(path->GetNSplines());

    for(int i=0; i<path->GetNSplines(); i++)
      {
	spline3_path[i] = dynamic_cast < const SplineSeg3<3>* >(&path->GetSpline(i));
	line_path[i] = dynamic_cast < const LineSeg<3>* >(&path->GetSpline(i));
	
	if(line_path[i])
	  {
	    y_dir[i] = line_path[i]->EndPI() - line_path[i]->StartPI();
	    y_dir[i].Normalize();
	    z_dir[i] = glob_z_direction;
	    Orthogonalize(y_dir[i],z_dir[i]);
	    x_dir[i] = Cross(y_dir[i],z_dir[i]);
	    loc_z_dir[i] = z_dir[i];
	  }
	else
	  {
	    z_dir[i] = glob_z_direction;
	    loc_z_dir[i] = glob_z_direction;
	  }
      }
    
    profile->GetCoeff(profile_spline_coeff);
    latest_point3d = -1.111e30;

  }

  
  ExtrusionFace :: ExtrusionFace(const SplineSeg<2> * profile_in,
				 const SplineGeometry<3> * path_in,
				 const Vec<3> & z_direction) :
    profile(profile_in), path(path_in), glob_z_direction(z_direction)
  {
    deletable = false;

    Init();
  }

  ExtrusionFace :: ExtrusionFace(const Array<double> & raw_data)
  {
    deletable = true;

    int pos=0;

    Array< Point<2> > p(3);

    int ptype = int(raw_data[pos]); pos++;

    for(int i=0; i<ptype; i++)
      {
	p[i](0) = raw_data[pos]; pos++;
	p[i](1) = raw_data[pos]; pos++;
      }
    if(ptype == 2)
      {
	profile = new LineSeg<2>(GeomPoint<2>(p[0],1),
				 GeomPoint<2>(p[1],1));
	//(*testout) << "appending LineSeg<2> " << p[0] 
	//	   << " to " << p[1] << endl;
      }
    else if(ptype == 3)
      {
	profile = new SplineSeg3<2>(GeomPoint<2>(p[0],1),
				    GeomPoint<2>(p[1],1),
				    GeomPoint<2>(p[2],1));
	//(*testout) << "appending SplineSeg<3> "
	//	   << p[0] << " -- " << p[1] << " -- " << p[2] << endl;
      }

    path = new SplineGeometry<3>;
    pos = const_cast< SplineGeometry<3> *>(path)->Load(raw_data,pos);

    for(int i=0; i<3; i++)
      {
	glob_z_direction(i) = raw_data[pos]; 
	pos++;
      }

    //(*testout) << "read glob_z_direction " << glob_z_direction << endl;
    
    Init();

  }

  ExtrusionFace :: ~ExtrusionFace()
  {
    if(deletable)
      {
	delete profile;
	delete path;
      }
  }

  
  int ExtrusionFace :: IsIdentic (const Surface & s2, int & inv, double eps) const
  {
    const ExtrusionFace * ext2 = dynamic_cast<const ExtrusionFace*>(&s2);

    if(!ext2) return 0;

    if(ext2 == this)
      return 1;

    return 0;
  } 
  
  void ExtrusionFace :: Orthogonalize(const Vec<3> & v1, Vec<3> & v2) const
  {
    v2 -= (v1*v2)*v1;
    v2.Normalize();
  }

  
  void ExtrusionFace :: CalcProj(const Point<3> & point3d, Point<2> & point2d,
				 int & seg, double & t) const
  {
    if(Dist2(point3d,latest_point3d) < 1e-25*Dist2(path->GetSpline(0).StartPI(),path->GetSpline(0).EndPI()))
      {
	point2d = latest_point2d;
	seg = latest_seg;
	t = latest_t;
	return;
      }
    
    latest_point3d = point3d;

    double cutdist(-1);
    

    

    Array<double> mindist(path->GetNSplines());

    for(int i=0; i<path->GetNSplines(); i++)
      {

	double auxcut(-1);
	double auxmin(-1);

	if(spline3_path[i])
	  {
	    Point<3> startp(path->GetSpline(i).StartPI());
	    Point<3> endp(path->GetSpline(i).EndPI());
	    Point<3> tanp(spline3_path[i]->TangentPoint());
	    double da,db,dc;

	    double l;
	    Vec<3> dir = endp-startp;
	    l = dir.Length(); dir *= 1./l;
	    Vec<3> topoint = point3d - startp;
	    double s = topoint * dir;
	    if(s<=0)
	      da = topoint.Length();
	    else if(s>=l)
	      da = Dist(endp,point3d);
	    else
	      da = sqrt(topoint.Length2() - s*s);

	    dir = tanp - startp;
	    l = dir.Length(); dir *= 1./l;
	    topoint = point3d - startp;
	    s = topoint * dir;
	    if(s<=0)
	      db = topoint.Length();
	    else if(s>=l)
	      db = Dist(tanp,point3d);
	    else
	      db = sqrt(topoint.Length2() - s*s);
	    
	    dir = endp - tanp;
	    l = dir.Length(); dir *= 1./l;
	    topoint = point3d - tanp;
	    s = topoint * dir;
	    if(s<=0)
	      dc = topoint.Length();
	    else if(s>=l)
	      dc = Dist(endp,point3d);
	    else
	      dc = sqrt(topoint.Length2() - s*s);
	    
	    if(da > db && da > dc)
	      auxcut = da;
	    else
	      auxcut = max2(da,min2(db,dc));

	    auxmin = min3(da,db,dc);
	  }
	else if(line_path[i])
	  {
	    double l;
	    Vec<3> dir = path->GetSpline(i).EndPI() - path->GetSpline(i).StartPI();
	    l = dir.Length(); dir *= 1./l;
	    Vec<3> topoint = point3d - path->GetSpline(i).StartPI();
	    double s = topoint * dir;
	    if(s<=0)
	      auxcut = topoint.Length();
	    else if(s>=l)
	      auxcut = Dist(path->GetSpline(i).EndPI(),point3d);
	    else
	      auxcut = sqrt(topoint.Length2() - s*s);

	    auxmin = auxcut;
	  }

	
	mindist[i] = auxmin;
	
	if(i==0 || auxcut < cutdist)
	  cutdist = auxcut;

	

	
	/*
	double d1 = Dist2(point3d,path.GetSpline(i).StartPI());
	double d2 = Dist2(point3d,path.GetSpline(i).EndPI());
	if(d1 <= d2)
	  {
	    mindist[i] = d1;
	    if(i==0 || d2 < cutdist)
	      cutdist = d2;
	  }
	else
	  {
	    mindist[i] = d2;
	    if(i==0 || d1 < cutdist)
	      cutdist = d1;
	  }
	*/
      }
	

    //(*testout) << " cutdist " << cutdist << " mindist " << mindist << endl;


    Point<2> testpoint2d;
    Point<3> testpoint3d;
    
    double minproj(-1);
    bool minproj_set(false);


    //(*testout) << "point "<< point3d << " candidates: ";
    for(int i=0; i<path->GetNSplines(); i++)
      {
	if(mindist[i] > cutdist) continue;
	//(*testout) << i << " ";

	double thist = CalcProj(point3d,testpoint2d,i);
	testpoint3d = p0[i] + testpoint2d(0)*x_dir[i] + testpoint2d(1)*loc_z_dir[i];
	double d = Dist2(point3d,testpoint3d);
	//(*testout) << "(d="<<d<<") ";

	if(!minproj_set || d < minproj)
	  {
	    minproj_set = true;
	    minproj = d;
	    point2d = testpoint2d;
	    t = thist;
	    seg = i;
	    latest_seg = i;
	    latest_t = t;
	    latest_point2d = point2d;
	  }
      }
    //(*testout) << endl;
    //(*testout) << " t " << t << endl;

  }

  double ExtrusionFace :: CalcProj(const Point<3> & point3d, Point<2> & point2d,
				   const int seg) const
  {
    double t(-1);

    if(line_path[seg])
      {
	point2d(0) = (point3d-line_path[seg]->StartPI())*x_dir[seg];
	point2d(1) = (point3d-line_path[seg]->StartPI())*z_dir[seg];
	double l = Dist(line_path[seg]->StartPI(),
			line_path[seg]->EndPI());
	t = min2(max2((point3d - line_path[seg]->StartPI()) * y_dir[seg],0.),
		 l);	
	p0[seg] = line_path[seg]->StartPI() + t*y_dir[seg];
	t *= 1./l;
      }
    else if(spline3_path[seg])
      {
	spline3_path[seg]->Project(point3d,p0[seg],t);
	
	y_dir[seg] = spline3_path[seg]->GetTangent(t); y_dir[seg].Normalize();
	loc_z_dir[seg] = z_dir[seg];
	Orthogonalize(y_dir[seg],loc_z_dir[seg]);
	x_dir[seg] = Cross(y_dir[seg],loc_z_dir[seg]);
	Vec<3> dir = point3d-p0[seg];
	point2d(0) = x_dir[seg]*dir;
	point2d(1) = loc_z_dir[seg]*dir;	
      }
    return t;
  }

  double ExtrusionFace :: CalcFunctionValue (const Point<3> & point) const
  {
    Point<2> p;

    double dummyd;
    int dummyi;

    CalcProj(point,p,dummyi,dummyd);
    //(*testout) << "spline " << dummyi << " t " << dummyd << endl;

    return profile_spline_coeff(0)*p(0)*p(0) + profile_spline_coeff(1)*p(1)*p(1)
      + profile_spline_coeff(2)*p(0)*p(1) + profile_spline_coeff(3)*p(0)
      + profile_spline_coeff(4)*p(1) + profile_spline_coeff(5);    
  }


  void ExtrusionFace :: CalcGradient (const Point<3> & point, Vec<3> & grad) const
  {
    int i;
    Point<2> p2d;

    double t_path;
    int seg;
    CalcProj(point,p2d,seg,t_path);

    Point<3> phi;
    Vec<3> phip,phipp,phi_minus_point;

    path->GetSpline(seg).GetDerivatives(t_path,phi,phip,phipp);

    phi_minus_point = phi-point;

    Vec<3> grad_t = phip;
    
    double facA = phipp*phi_minus_point + phip*phip;

    grad_t *= 1./facA;

    Array < Vec<3> > dphi_dX(3);
    
    for(i=0; i<3; i++)
      dphi_dX[i] = grad_t(i)*phip;

    Array < Vec<3> > dy_dir_dX(3);

    double lphip = phip.Length();

    dy_dir_dX[0] = dy_dir_dX[1] = dy_dir_dX[2] =
      (1./lphip) * phipp - ((phip*phipp)/pow(lphip,3)) * phip;

    for(i=0; i<3; i++)
      dy_dir_dX[i] *= grad_t(i);

    Array < Vec<3> > dx_dir_dX(3);

    for(i=0; i<3; i++)
      dx_dir_dX[i] = Cross(dy_dir_dX[i],z_dir[seg]);

    Vec<3> grad_xbar;

    for(i=0; i<3; i++)
      grad_xbar(i) = -1.*(phi_minus_point * dx_dir_dX[i]) + x_dir[seg](i) - x_dir[seg] * dphi_dX[i];

    double zy = z_dir[seg]*y_dir[seg];

    Vec<3> grad_ybar;
    Vec<3> aux = z_dir[seg] - zy*y_dir[seg];

    for(i=0; i<3; i++)
      grad_ybar(i) = ( (z_dir[seg]*dy_dir_dX[i])*y_dir[seg] + zy*dy_dir_dX[i] ) * phi_minus_point +
	aux[i] -
	aux * dphi_dX[i];

    
    const double dFdxbar = 2.*profile_spline_coeff(0)*p2d(0) +
      profile_spline_coeff(2)*p2d(1) + profile_spline_coeff(3);

    const double dFdybar = 2.*profile_spline_coeff(1)*p2d(1) +
      profile_spline_coeff(2)*p2d(0) + profile_spline_coeff(4);
    

    grad = dFdxbar * grad_xbar + dFdybar * grad_ybar;    
  }

  void ExtrusionFace :: CalcHesse (const Point<3> & point, Mat<3> & hesse) const
  {
    const double eps = 1e-7*Dist(path->GetSpline(0).StartPI(),path->GetSpline(0).EndPI());
    
    /*
    Point<3> auxpoint1(point),auxpoint2(point);
    Vec<3> auxvec,auxgrad1,auxgrad2;

    for(int i=0; i<3; i++)
      {
	auxpoint1(i) -= eps;
	auxpoint2(i) += eps;
	CalcGradient(auxpoint1,auxgrad1);
	CalcGradient(auxpoint2,auxgrad2);
	auxvec = (1./(2.*eps)) * (auxgrad2-auxgrad1);
	for(int j=0; j<3; j++)
	  hesse(i,j) = auxvec(j);
	auxpoint1(i) = point(i);
	auxpoint2(i) = point(i);
      }
    */

 
    Vec<3> grad;
    CalcGradient(point,grad);

    Point<3> auxpoint(point);
    Vec<3> auxvec,auxgrad;

    for(int i=0; i<3; i++)
      {
	auxpoint(i) -= eps;
	CalcGradient(auxpoint,auxgrad);
	auxvec = (1./eps) * (grad-auxgrad);
	for(int j=0; j<3; j++)
	  hesse(i,j) = auxvec(j);
	auxpoint(i) = point(i);
      }
 

    
    for(int i=0; i<3; i++)
      for(int j=i+1; j<3; j++)
	hesse(i,j) = hesse(j,i) = 0.5*(hesse(i,j)+hesse(j,i));
  }
  


  double ExtrusionFace :: HesseNorm () const
  {
    return fabs(profile_spline_coeff(0) + profile_spline_coeff(1)) +
      sqrt(pow(profile_spline_coeff(0)+profile_spline_coeff(1),2)+4.*pow(profile_spline_coeff(2),2));
  }

  double ExtrusionFace :: MaxCurvature () const
  {
    double retval,actmax;
    
    retval = profile->MaxCurvature();
    for(int i=0; i<path->GetNSplines(); i++)
      {
	actmax = path->GetSpline(i).MaxCurvature();
	if(actmax > retval)
	  retval = actmax;
      }

    return 2.*retval;
  }


  void ExtrusionFace :: Project (Point<3> & p) const
  {
    double dummyt;
    int seg;
    Point<2> p2d;

    CalcProj(p,p2d,seg,dummyt);

    profile->Project(p2d,p2d,profile_par);
    
    p = p0[seg] + p2d(0)*x_dir[seg] + p2d(1)*loc_z_dir[seg];
    
    Vec<2> tangent2d = profile->GetTangent(profile_par);
    profile_tangent = tangent2d(0)*x_dir[seg] + tangent2d(1)*y_dir[seg];
  }


  
  Point<3> ExtrusionFace :: GetSurfacePoint () const
  {
    p0[0] = path->GetSpline(0).GetPoint(0.5);
    if(!line_path[0])
      {
	y_dir[0] = path->GetSpline(0).GetTangent(0.5);
	y_dir[0].Normalize();
	loc_z_dir[0] = z_dir[0];
	Orthogonalize(y_dir[0],loc_z_dir[0]);
	x_dir[0] = Cross(y_dir[0],loc_z_dir[0]);
      }

    Point<2> locpoint = profile->GetPoint(0.5);

    return p0[0] + locpoint(0)*x_dir[0] + locpoint(1)*loc_z_dir[0];
  }

  bool ExtrusionFace :: BoxIntersectsFace(const Box<3> & box) const
  {
    Point<3> center = box.Center();

    Project(center);

    //(*testout) << "box.Center() " << box.Center() << " projected " << center << " diam " << box.Diam() 
    //       << " dist " << Dist(box.Center(),center) << endl;

    return (Dist(box.Center(),center) < 0.5*box.Diam());
  }


  void ExtrusionFace :: LineIntersections ( const Point<3> & p,
					    const Vec<3> & v,
					    const double eps,
					    int & before,
					    int & after,
					    bool & intersecting ) const
  {
    Point<2> p2d;
    Vec<2> v2d;

    intersecting = false;

    double segt;
    int seg;

    CalcProj(p,p2d,seg,segt);

    if(seg == 0 && segt < 1e-20)
      {
	Vec<3> v1,v2;
	v1 = path->GetSpline(0).GetTangent(0);
	v2 = p-p0[seg];
	if(v1*v2 < -eps)
	  return;
      }
    if(seg == path->GetNSplines()-1 && 1.-segt < 1e-20)
      {
	Vec<3> v1,v2;
	v1 = path->GetSpline(seg).GetTangent(1);
	v2 = p-p0[seg];
	if(v1*v2 > eps)
	  return;
      }

    v2d(0) = v * x_dir[seg];
    v2d(1) = v * loc_z_dir[seg];
    
    Vec<2> n(v2d(1),-v2d(0));
    Array < Point<2> > ips;


    profile->LineIntersections(v2d(1),
			      -v2d(0),
			      -v2d(1)*p2d(0) + v2d(0)*p2d(1),
			      ips,eps);
    int comp;

    if(fabs(v2d(0)) >= fabs(v2d(1)))
      comp = 0;
    else
      comp = 1;

    //(*testout) << "p2d " << p2d;

    for(int i=0; i<ips.Size(); i++)
      {
	//(*testout) << " ip " << ips[i];

	double t = (ips[i](comp)-p2d(comp))/v2d(comp);

	if(t < -eps)
	  before++;
	else if(t > eps)
	  after++;
	else
	  intersecting = true;
      }
    //(*testout) << endl;
  }

  void ExtrusionFace :: Print (ostream & str) const{}

  INSOLID_TYPE ExtrusionFace :: VecInFace ( const Point<3> & p,
					    const Vec<3> & v,
					    const double eps ) const
  {
    
    Vec<3> normal1;
    CalcGradient(p,normal1); normal1.Normalize();

    double d1 = normal1*v;


    if(d1 > eps)
      return IS_OUTSIDE;
    if(d1 < -eps)
      return IS_INSIDE;
    

    return DOES_INTERSECT;

    /*
    Point<2> p2d;

    double t_path;
    int seg;
    CalcProj(p,p2d,seg,t_path);

    double t;
    profile.Project(p2d,p2d,t);


    
    Vec<2> profile_tangent = profile.GetTangent(t);

    double d;

    Vec<3> normal1;
    CalcGradient(p,normal1); normal1.Normalize();

    double d1 = normal1*v;

    Vec<2> v2d;

    v2d(0) = v*x_dir[seg];
    v2d(1) = v*loc_z_dir[seg];

			    	    
    Vec<2> normal(-profile_tangent(1),profile_tangent(0));
    
    //d = normal*v2d;
    

    d = d1;


    if(d > eps)
      return IS_OUTSIDE;
    if(d < -eps)
      return IS_INSIDE;
    

    return DOES_INTERSECT;
    */
  }


  void ExtrusionFace :: GetTriangleApproximation (TriangleApproximation & tas, 
						  const Box<3> & boundingbox, 
						  double facets) const
  {
    int n = int(facets) + 1;
    
    int i,j,k;
    
    
    int nump = 0;
    for(k=0; k<path->GetNSplines(); k++)
      {
	for(i=0; i<=n; i++)
	  {
	    Point<3> origin = path->GetSpline(k).GetPoint(double(i)/double(n));
	    if(!line_path[k])
	      {
		y_dir[k] = path->GetSpline(k).GetTangent(double(i)/double(n));
		y_dir[k].Normalize();
	      }
	    loc_z_dir[k] = z_dir[k];
	    Orthogonalize(y_dir[k],loc_z_dir[k]);
	    if(!line_path[k])
	      x_dir[k] = Cross(y_dir[k],loc_z_dir[k]);
	    
	    for(j=0; j<=n; j++)
	      {
		Point<2> locp = profile->GetPoint(double(j)/double(n));
		tas.AddPoint(origin + locp(0)*x_dir[k] + locp(1)*loc_z_dir[k]);
		nump++;
	      }
	  }
      }
    
    for(k=0; k<path->GetNSplines(); k++)
      for(i=0; i<n; i++)
	for(j=0; j<n; j++)
	  {
	    int pi = k*(n+1)*(n+1) + (n+1)*i +j;
	  
	    tas.AddTriangle( TATriangle (0, pi,pi+1,pi+n+1));
	    tas.AddTriangle( TATriangle (0, pi+1,pi+n+1,pi+n+2));
	  }
  }
  

  void ExtrusionFace :: GetRawData(Array<double> & data) const
  {
    data.DeleteAll();
    profile->GetRawData(data);
    path->GetRawData(data);
    for(int i=0; i<3; i++)
      data.Append(glob_z_direction[i]);
    //(*testout) << "written raw data " << data << endl;
  }



  Extrusion :: Extrusion(const SplineGeometry<3> & path_in,
			 const SplineGeometry<2> & profile_in,
			 const Vec<3> & z_dir) :
    path(path_in), profile(profile_in), z_direction(z_dir)
  {
    surfaceactive.SetSize(0);
    surfaceids.SetSize(0);

    for(int j=0; j<profile.GetNSplines(); j++)
      {
	ExtrusionFace * face = new ExtrusionFace(&(profile.GetSpline(j)),
						 &path,
						 z_direction);
	faces.Append(face);
	surfaceactive.Append(true);
	surfaceids.Append(0);
      }

  }


  Extrusion :: ~Extrusion()
  {
    for(int i=0; i<faces.Size(); i++)
      delete faces[i];
  }





  INSOLID_TYPE Extrusion :: BoxInSolid (const BoxSphere<3> & box) const
  {
    for(int i=0; i<faces.Size(); i++)
      {
	if(faces[i]->BoxIntersectsFace(box))
	  return DOES_INTERSECT;
      }

    return PointInSolid(box.Center(),0);
  }


  INSOLID_TYPE Extrusion :: PointInSolid (const Point<3> & p,
					  const double eps,
					  Array<int> * const facenums) const
  {
    Vec<3> random_vec(-0.4561,0.7382,0.4970247);

    int before(0), after(0);
    bool intersects(false);
    bool does_intersect(false);

    for(int i=0; i<faces.Size(); i++)
      {
	faces[i]->LineIntersections(p,random_vec,eps,before,after,intersects);

	//(*testout) << "intersects " << intersects << " before " << before << " after " << after << endl;
	if(intersects)
	  {
	    if(facenums)
	      {
		facenums->Append(i);
		does_intersect = true;
	      }
	    else
	      return DOES_INTERSECT;
	  }
      }

    if(does_intersect)
      return DOES_INTERSECT;


    if(before % 2 == 0)
      return IS_OUTSIDE;

    return IS_INSIDE;
  }


  INSOLID_TYPE Extrusion :: PointInSolid (const Point<3> & p,
					  double eps) const
  {
    return PointInSolid(p,eps,NULL);    
  }

  INSOLID_TYPE Extrusion :: VecInSolid (const Point<3> & p,
					const Vec<3> & v,
					double eps) const
  {
    Array<int> facenums;
    INSOLID_TYPE pInSolid = PointInSolid(p,eps,&facenums);

    if(pInSolid != DOES_INTERSECT)
      return pInSolid;


    double d(0);

    if(facenums.Size() == 1)
      {
	Vec<3> normal;
	faces[facenums[0]]->CalcGradient(p,normal);
	normal.Normalize();
	d = normal*v;
	
	latestfacenum = facenums[0];
      }
    else if (facenums.Size() == 2)
      {
	Vec<3> checkvec;

	Point<3> dummy(p);
	faces[facenums[0]]->Project(dummy);
	if(fabs(faces[facenums[0]]->GetProfilePar()) < 0.1)
	  {
	    int aux = facenums[0];
	    facenums[0] = facenums[1]; facenums[1] = aux;
	  }
	
	checkvec = faces[facenums[0]]->GetYDir();
     
	Vec<3> n0, n1;
	faces[facenums[0]]->CalcGradient(p,n0);
	faces[facenums[1]]->CalcGradient(p,n1);
	n0.Normalize();
	n1.Normalize();
	

	Vec<3> t = Cross(n0,n1);
	if(checkvec*t < 0) t*= (-1.);
	
	Vec<3> t0 = Cross(n0,t);
	Vec<3> t1 = Cross(t,n1);
	
	t0.Normalize();
	t1.Normalize();
	

	const double t0v = t0*v;
	const double t1v = t1*v;

	if(t0v > t1v)
	  {
	    latestfacenum = facenums[0];
	    d = n0*v;
	  }
	else
	  {
	    latestfacenum = facenums[1];
	    d = n1*v;
	  }

	if(fabs(t0v) < eps && fabs(t1v) < eps)
	  latestfacenum = -1;
      }

    else
      {
	cerr << "WHY ARE THERE " << facenums.Size() << " FACES?" << endl;
      }

    if(d > eps)
      return IS_OUTSIDE;
    if(d < -eps)
      return IS_INSIDE;
      
    return DOES_INTERSECT;
  }



  // checks if lim s->0 lim t->0  p + t(v1 + s v2) in solid
  INSOLID_TYPE Extrusion :: VecInSolid2 (const Point<3> & p,
					 const Vec<3> & v1,
					 const Vec<3> & v2,
					 double eps) const
  {
    INSOLID_TYPE retval;
    retval = VecInSolid(p,v1,eps);

    // *testout << "extr, vecinsolid=" << int(retval) << endl;

    if(retval != DOES_INTERSECT)
      return retval;

    if(latestfacenum >= 0)
      return faces[latestfacenum]->VecInFace(p,v2,0);
    else
      return VecInSolid(p,v2,eps);
  }

  
  int Extrusion :: GetNSurfaces() const
  {
    return faces.Size();
  }

  Surface & Extrusion :: GetSurface (int i)
  {
    return *faces[i];
  }

  const Surface & Extrusion :: GetSurface (int i) const
  {
    return *faces[i];
  }


  void Extrusion :: Reduce (const BoxSphere<3> & box)
  {
    for(int i=0; i<faces.Size(); i++)
      surfaceactive[i] = faces[i]->BoxIntersectsFace(box);
  }

  void Extrusion :: UnReduce ()
  {
    for(int i=0; i<faces.Size(); i++)
      surfaceactive[i] = true;
  }


}