orientation_2.h

很多二维 三维几何计算算法 C++ 类库

// Copyright (c) 2001,2004  INRIA Sophia-Antipolis (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org); 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; version 2.1 of the License.
// See the file LICENSE.LGPL distributed with CGAL.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL: svn+ssh://scm.gforge.inria.fr/svn/cgal/branches/CGAL-3.3-branch/Filtered_kernel/include/CGAL/Static_filters/Orientation_2.h $
// $Id: Orientation_2.h 35070 2006-11-06 17:12:11Z spion $
// 
//
// Author(s)     : Sylvain Pion

#ifndef CGAL_STATIC_FILTERS_ORIENTATION_2_H
#define CGAL_STATIC_FILTERS_ORIENTATION_2_H

#include <CGAL/Profile_counter.h>
#include <CGAL/Static_filter_error.h>

#include <cmath>

CGAL_BEGIN_NAMESPACE

template < typename K_base >
class SF_Orientation_2
  : public K_base::Orientation_2
{
  typedef typename K_base::Point_2          Point_2;
  typedef typename K_base::Vector_2         Vector_2;
  typedef typename K_base::Circle_2          Circle_2;

  typedef typename K_base::Orientation_2    Base;

public:

  typedef typename Base::result_type  result_type;

#ifndef CGAL_CFG_MATCHING_BUG_6
  using Base::operator();
#else 
  result_type
  operator()(const Vector_2& u, const Vector_2& v) const
  { 
    return Base::operator()(u,v);
  }
  
  result_type
  operator()(const Circle_2& c) const
  {
    return Base::operator()(c);
  }
#endif
  Orientation
  operator()(const Point_2 &p, const Point_2 &q, const Point_2 &r) const

  {
      CGAL_PROFILER("Orientation_2 calls");

      double px, py, qx, qy, rx, ry;

      if (fit_in_double(p.x(), px) && fit_in_double(p.y(), py) &&
          fit_in_double(q.x(), qx) && fit_in_double(q.y(), qy) &&
          fit_in_double(r.x(), rx) && fit_in_double(r.y(), ry))
      {
          CGAL_PROFILER("Orientation_2 semi-static attempts");

          double pqx = qx - px;
          double pqy = qy - py;
          double prx = rx - px;
          double pry = ry - py;

          double det = det2x2_by_formula(pqx, pqy,
                                         prx, pry);

          // Then semi-static filter.
          double maxx = std::fabs(pqx);
          if (maxx < std::fabs(prx)) maxx = std::fabs(prx);
          double maxy = std::fabs(pqy);
          if (maxy < std::fabs(pry)) maxy = std::fabs(pry);
          double eps = 8.8872057372592798e-16 * maxx * maxy;

          // Sort them
          if (maxx > maxy)  std::swap(maxx, maxy);

          // Protect against underflow in the computation of eps.
          if (maxx < 1e-146) /* sqrt(min_double/eps) */ {
            if (maxx == 0)
              return ZERO;
          }
          // Protect against overflow in the computation of det.
          else if (maxy < 1e153) /* sqrt(max_double [hadamard]/2) */ {
            if (det > eps)  return POSITIVE;
            if (det < -eps) return NEGATIVE;
          }

          CGAL_PROFILER("Orientation_2 semi-static failures");
      }

      return Base::operator()(p, q, r);
  }

  // Computes the epsilon for Orientation_2.
  static double compute_epsilon()
  {
    typedef Static_filter_error F;
    F t1 = F(1, F::ulp()/2);         // First translation
    F det = det2x2_by_formula(t1, t1,
                              t1, t1); // Full det
    double err = det.error();
    err += err * 2 * F::ulp(); // Correction due to "epsilon * maxx * maxy".
    std::cerr << "*** epsilon for Orientation_2 = " << err << std::endl;
    return err;
  }
};

CGAL_END_NAMESPACE

#endif // CGAL_STATIC_FILTERS_ORIENTATION_2_H