1 // Copyright (C) 2007-2021 CEA/DEN, EDF R&D
3 // This library is free software; you can redistribute it and/or
4 // modify it under the terms of the GNU Lesser General Public
5 // License as published by the Free Software Foundation; either
6 // version 2.1 of the License, or (at your option) any later version.
8 // This library is distributed in the hope that it will be useful,
9 // but WITHOUT ANY WARRANTY; without even the implied warranty of
10 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 // Lesser General Public License for more details.
13 // You should have received a copy of the GNU Lesser General Public
14 // License along with this library; if not, write to the Free Software
15 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
17 // See http://www.salome-platform.org/ or email : webmaster.salome@opencascade.com
29 constexpr double BBTREE_DFT_EPSILON = 1e-12;
31 template <int dim, class ConnType = int>
42 typename std::vector<ConnType> _elems;
47 static const int MIN_NB_ELEMS=15;
48 static const int MAX_LEVEL=20;
52 Constructor of the bounding box tree
53 \param bbs pointer to the [xmin1 xmax1 ymin1 ymax1 xmin2 xmax2 ...] array containing the bounding boxes that are to be indexed.
54 \param elems array to the indices of the elements contained in the BBTree
55 \param level level in the BBTree recursive structure
56 \param nbelems nb of elements in the BBTree
57 \param epsilon precision to which points are decided to be coincident. Epsilon can be positive or negative.
58 If \a epsilon is positive the request method will enlarge the computed bounding box (more matching elems return).
59 If negative the given bounding box will be tighten (less matching elems return).
61 Parameters \a elems and \a level are used only by BBTree itself for creating trees recursively. A typical use is therefore :
64 double* bbs= new double[2*2*nbelems];
67 BBTree<2> tree = new BBTree<2>(elems,0,0,nbelems,1e-12);
71 BBTree(const double* bbs, ConnType* elems, int level, ConnType nbelems, double epsilon=BBTREE_DFT_EPSILON):
72 _left(0), _right(0), _level(level), _bb(bbs), _terminal(false),_nbelems(nbelems),_epsilon(epsilon)
74 if (nbelems < MIN_NB_ELEMS || level> MAX_LEVEL)
79 double* nodes=new double [nbelems];
80 _elems.resize(nbelems);
81 for (ConnType i=0; i<nbelems; i++)
90 nodes[i]=bbs[elem*dim*2+(level%dim)*2];
92 if (_terminal) { delete[] nodes; return;}
94 std::nth_element<double*>(nodes, nodes+nbelems/2, nodes+nbelems);
95 double median = *(nodes+nbelems/2);
97 // std:: cout << *median <<std::endl;
99 std::vector<ConnType> new_elems_left;
100 std::vector<ConnType> new_elems_right;
102 new_elems_left.reserve(nbelems/2+1);
103 new_elems_right.reserve(nbelems/2+1);
104 double max_left = -std::numeric_limits<double>::max();
105 double min_right= std::numeric_limits<double>::max();
106 for (ConnType i=0; i<nbelems;i++)
113 double max=bbs[elem*dim*2+(level%dim)*2+1];
114 double min = bbs[elem*dim*2+(level%dim)*2];
118 new_elems_right.push_back(elem);
119 if (min<min_right) min_right = min;
124 new_elems_left.push_back(elem);
125 if (max>max_left) max_left = max;
130 _max_left=max_left+std::abs(_epsilon);
131 _min_right=min_right-std::abs(_epsilon);
134 if(!new_elems_left.empty())
135 tmp=&(new_elems_left[0]);
136 _left=new BBTree(bbs, tmp, level+1, (ConnType)new_elems_left.size(),_epsilon);
138 if(!new_elems_right.empty())
139 tmp=&(new_elems_right[0]);
140 _right=new BBTree(bbs, tmp, level+1, (ConnType)new_elems_right.size(),_epsilon);
148 if (_left!=0) delete _left;
149 if (_right!=0) delete _right;
154 /*! returns in \a elems the list of elements potentially intersecting the bounding box pointed to by \a bb
156 \param bb pointer to query bounding box
157 \param elems list of elements (given in 0-indexing that is to say in \b C \b mode) intersecting the bounding box
160 void getIntersectingElems(const double* bb, std::vector<ConnType>& elems) const
162 // terminal node : return list of elements intersecting bb
165 for (ConnType i=0; i<_nbelems; i++)
167 const double* const bb_ptr=_bb+_elems[i]*2*dim;
168 bool intersects = true;
169 for (int idim=0; idim<dim; idim++)
171 if (bb_ptr[idim*2]-bb[idim*2+1]>-_epsilon|| bb_ptr[idim*2+1]-bb[idim*2]<_epsilon)
176 elems.push_back(_elems[i]);
183 double min = bb[(_level%dim)*2];
184 double max = bb[(_level%dim)*2+1];
185 if (max < _min_right)
187 _left->getIntersectingElems(bb, elems);
192 _right->getIntersectingElems(bb,elems);
195 _left->getIntersectingElems(bb,elems);
196 _right->getIntersectingElems(bb,elems);
200 * This method is very close to getIntersectingElems except that it returns number of elems instead of elems themselves.
202 ConnType getNbOfIntersectingElems(const double* bb)
204 // terminal node : return list of elements intersecting bb
208 for (ConnType i=0; i<_nbelems; i++)
210 const double* const bb_ptr=_bb+_elems[i]*2*dim;
211 bool intersects = true;
212 for (int idim=0; idim<dim; idim++)
214 if (bb_ptr[idim*2]-bb[idim*2+1]>-_epsilon|| bb_ptr[idim*2+1]-bb[idim*2]<_epsilon)
223 double min = bb[(_level%dim)*2];
224 double max = bb[(_level%dim)*2+1];
225 if (max < _min_right)
226 return _left->getNbOfIntersectingElems(bb);
228 return _right->getNbOfIntersectingElems(bb);
229 return _left->getNbOfIntersectingElems(bb)+_right->getNbOfIntersectingElems(bb);
233 /*! returns in \a elems the list of elements potentially containing the point pointed to by \a xx
234 \param xx pointer to query point coords
235 \param elems list of elements (given in 0-indexing) intersecting the bounding box
238 void getElementsAroundPoint(const double* xx, std::vector<ConnType>& elems) const
240 // terminal node : return list of elements intersecting bb
243 for (ConnType i=0; i<_nbelems; i++)
245 const double* const bb_ptr=_bb+_elems[i]*2*dim;
246 bool intersects = true;
247 for (int idim=0; idim<dim; idim++)
249 if (bb_ptr[idim*2]-xx[idim]>_epsilon|| bb_ptr[idim*2+1]-xx[idim]<-_epsilon)
254 elems.push_back(_elems[i]);
261 if (xx[_level%dim] < _min_right)
263 _left->getElementsAroundPoint(xx, elems);
266 if (xx[_level%dim]> _max_left)
268 _right->getElementsAroundPoint(xx,elems);
271 _left->getElementsAroundPoint(xx,elems);
272 _right->getElementsAroundPoint(xx,elems);
279 if (_terminal) return _nbelems;
280 return _left->size()+_right->size();