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Mesh Oriented datABase
(version 5.5.1)
An array-based unstructured mesh library
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|
Mesh Oriented datABase
(version 5.5.1)
An array-based unstructured mesh library
|
1 /**
2 * bvh_tree.hpp
3 * Ryan H. Lewis
4 * (C) 2012
5 *
6 * An element tree partitions a mesh composed of elements.
7 * We subdivide the bounding box of a me, by putting boxes
8 * on the left if there center is on the left of a split line
9 * and vice versa.
10 */
11 #include <vector>
12 #include <set>
13 #include <iostream>
14 #include <map>
15 #include <algorithm>
16 #include <bitset>
17 #include <numeric>
18 #include <cmath>
19 #include <tr1/unordered_map>
20 #include <limits>
21 #include "common_tree.hpp"
22
23 //#define BVH_TREE_DEBUG
24 #ifndef BVH_TREE_HPP
25 #define BVH_TREE_HPP
26
27 namespace ct = moab::common_tree;
28
29 namespace moab
30 {
31
32 // forward declarations
33 template < typename _Entity_handles, typename _Box, typename _Moab, typename _Parametrizer >
34 class Bvh_tree;
35
36 // non-exported functionality
37 namespace
38 {
39 namespace _bvh
40 {
41 template < typename Box, typename Entity_handle >
42 struct _Node
43 {
44 typedef typename std::vector< std::pair< Box, Entity_handle > > Entities;
45 std::size_t dim;
46 std::size_t child;
47 double Lmax, Rmin;
48 Entities entities;
49 _Node& operator=( const _Node& f )
50 {
51 dim = f.dim;
52 child = f.child;
53 Lmax = f.Lmax;
54 Rmin = f.Rmin;
55 entities = f.entities;
56 return *this;
57 }
58 }; // _Node
59
60 template < typename Split >
61 class Split_comparator
62 {
63 // deprecation of binary_function
64 typedef Split first_argument_type;
65 typedef Split second_argument_type;
66 typedef bool result_type;
67
68 inline double objective( const Split& a ) const
69 {
70 return a.Lmax * a.nl - a.Rmin * a.nr;
71 }
72
73 public:
74 bool operator()( const Split& a, const Split& b ) const
75 {
76 return objective( a ) < objective( b );
77 }
78 }; // Split_comparator
79
80 template < typename Iterator >
81 class Iterator_comparator
82 {
83 // deprecation of binary_function
84 typedef Iterator first_argument_type;
85 typedef Iterator second_argument_type;
86 typedef bool result_type;
87
88 public:
89 bool operator()( const Iterator& a, const Iterator& b ) const
90 {
91 return a->second.second < b->second.second ||
92 ( !( b->second.second < a->second.second ) && a->first < b->first );
93 }
94 }; // Split_comparator
95
96 class _Split_data
97 {
98 public:
99 typedef ct::Box< double > Box;
100 _Split_data()
101 : dim( 0 ), nl( 0 ), nr( 0 ), split( 0.0 ), Lmax( 0.0 ), Rmin( 0.0 ), bounding_box(), left_box(),
102 right_box()
103 {
104 }
105 _Split_data( const _Split_data& f )
106 : dim( f.dim ), nl( f.nl ), nr( f.nr ), split( f.split ), Lmax( f.Lmax ), Rmin( f.Rmin ),
107 bounding_box( f.bounding_box ), left_box( f.left_box ), right_box( f.right_box )
108 {
109 }
110 std::size_t dim;
111 std::size_t nl;
112 std::size_t nr;
113 double split;
114 double Lmax, Rmin;
115 Box bounding_box;
116 Box left_box;
117 Box right_box;
118 _Split_data& operator=( const _Split_data& f )
119 {
120 dim = f.dim;
121 nl = f.nl;
122 nr = f.nr;
123 split = f.split;
124 Lmax = f.Lmax;
125 Rmin = f.Rmin;
126 bounding_box = f.bounding_box;
127 left_box = f.left_box;
128 right_box = f.right_box;
129 return *this;
130 }
131 }; //_Split_data
132
133 class _Bucket
134 {
135 public:
136 _Bucket() : size( 0 ), bounding_box() {}
137 _Bucket( const _Bucket& f ) : size( f.size ), bounding_box( f.bounding_box ) {}
138 _Bucket( const std::size_t size_ ) : size( size_ ), bounding_box() {}
139 std::size_t size;
140 ct::Box< double > bounding_box;
141 _Bucket& operator=( const _Bucket& f )
142 {
143 bounding_box = f.bounding_box;
144 size = f.size;
145 return *this;
146 }
147 }; //_Split_data
148 } // namespace _bvh
149 } // namespace
150
151 template < typename _Entity_handles, typename _Box, typename _Moab, typename _Parametrizer >
152 class Bvh_tree
153 {
154 // public types
155 public:
156 typedef _Entity_handles Entity_handles;
157 typedef _Box Box;
158 typedef _Moab Moab;
159 typedef _Parametrizer Parametrizer;
160 typedef typename Entity_handles::value_type Entity_handle;
161
162 // private types
163 private:
164 typedef Bvh_tree< _Entity_handles, _Box, _Moab, _Parametrizer > Self;
165 typedef typename std::pair< Box, Entity_handle > Leaf_element;
166 typedef _bvh::_Node< Box, Entity_handle > Node;
167 typedef typename std::vector< Node > Nodes;
168 // public methods
169 public:
170 // Constructor
171 Bvh_tree( Entity_handles& _entities, Moab& _moab, Box& _bounding_box, Parametrizer& _entity_contains )
172 : entity_handles_( _entities ), tree_(), moab( _moab ), bounding_box( _bounding_box ),
173 entity_contains( _entity_contains )
174 {
175 typedef typename Entity_handles::iterator Entity_handle_iterator;
176 typedef ct::_Element_data< const _Box, double > Element_data;
177 typedef typename std::tr1::unordered_map< Entity_handle, Element_data > Entity_map;
178 typedef typename Entity_map::iterator Entity_map_iterator;
179 typedef std::vector< Entity_map_iterator > Vector;
180 // a fully balanced tree will have 2*_entities.size()
181 // which is one doubling away..
182 tree_.reserve( entity_handles_.size() );
183 Entity_map entity_map( entity_handles_.size() );
184 ct::construct_element_map( entity_handles_, entity_map, bounding_box, moab );
185 #ifdef BVH_TREE_DEBUG
186 for( Entity_map_iterator i = entity_map.begin(); i != entity_map.end(); ++i )
187 {
188 if( !box_contains_box( bounding_box, i->second.first, 0 ) )
189 {
190 std::cerr << "BB:" << bounding_box << "EB:" << i->second.first << std::endl;
191 std::exit( -1 );
192 }
193 }
194 #endif
195 //_bounding_box = bounding_box;
196 Vector entity_ordering;
197 construct_ordering( entity_map, entity_ordering );
198 // We only build nonempty trees
199 if( entity_ordering.size() )
200 {
201 // initially all bits are set
202 tree_.push_back( Node() );
203 const int depth = build_tree( entity_ordering.begin(), entity_ordering.end(), 0, bounding_box );
204 #ifdef BVH_TREE_DEBUG
205 typedef typename Nodes::iterator Node_iterator;
206 typedef typename Node::Entities::iterator Entity_iterator;
207 std::set< Entity_handle > entity_handles;
208 for( Node_iterator i = tree_.begin(); i != tree_.end(); ++i )
209 {
210 for( Entity_iterator j = i->entities.begin(); j != i->entities.end(); ++j )
211 {
212 entity_handles.insert( j->second );
213 }
214 }
215 if( entity_handles.size() != entity_handles_.size() )
216 {
217 std::cout << "Entity Handle Size Mismatch!" << std::endl;
218 }
219 typedef typename Entity_handles::iterator Entity_iterator_;
220 for( Entity_iterator_ i = entity_handles_.begin(); i != entity_handles_.end(); ++i )
221 {
222 if( entity_handles.find( *i ) == entity_handles.end() )
223 {
224 std::cout << "Tree is missing an entity! " << std::endl;
225 }
226 }
227
228 #endif
229 std::cout << "max tree depth: " << depth << std::endl;
230 }
231 }
232
233 // Copy constructor
234 Bvh_tree( Self& s )
235 : entity_handles_( s.entity_handles_ ), tree_( s.tree_ ), moab( s.moab ), bounding_box( s.bounding_box ),
236 entity_contains( s.entity_contains )
237 {
238 }
239
240 // see FastMemoryEfficientCellLocationinUnstructuredGridsForVisualization.pdf
241 // around page 9
242 #define NUM_SPLITS 4
243 #define NUM_BUCKETS ( NUM_SPLITS + 1 ) // NUM_SPLITS+1
244 #define SMAX 5
245 // Paper arithmetic is over-optimized.. this is safer.
246 template < typename Box >
247 std::size_t bucket_index( const Box& box, const Box& interval, const std::size_t dim ) const
248 {
249 const double min = interval.min[dim];
250 const double length = ( interval.max[dim] - min ) / NUM_BUCKETS;
251 const double center = ( ( box.max[dim] + box.min[dim] ) / 2.0 ) - min;
252 #ifdef BVH_TREE_DEBUG
253 #ifdef BVH_SHOW_INDEX
254 std::cout << "[ " << min << " , " << interval.max[dim] << " ]" << std::endl;
255 std::cout << "[ " << box.min[dim] << " , " << box.max[dim] << " ]" << std::endl;
256 std::cout << "Length of bucket" << length << std::endl;
257 std::cout << "Center: " << ( box.max[dim] + box.min[dim] ) / 2.0 << std::endl;
258 std::cout << "Distance of center from min: " << center << std::endl;
259 std::cout << "ratio: " << center / length << std::endl;
260 std::cout << "index: " << std::ceil( center / length ) - 1 << std::endl;
261 #endif
262 #endif
263 return std::ceil( center / length ) - 1;
264 }
265
266 template < typename Iterator, typename Bounding_box, typename Buckets >
267 void establish_buckets( const Iterator begin,
268 const Iterator end,
269 const Bounding_box& interval,
270 Buckets& buckets ) const
271 {
272 // put each element into its bucket
273 for( Iterator i = begin; i != end; ++i )
274 {
275 const Bounding_box& box = ( *i )->second.first;
276 for( std::size_t dim = 0; dim < NUM_DIM; ++dim )
277 {
278 const std::size_t index = bucket_index( box, interval, dim );
279 _bvh::_Bucket& bucket = buckets[dim][index];
280 if( bucket.size > 0 )
281 {
282 ct::update_bounding_box( bucket.bounding_box, box );
283 }
284 else
285 {
286 bucket.bounding_box = box;
287 }
288 bucket.size++;
289 }
290 }
291 #ifdef BVH_TREE_DEBUG
292 Bounding_box elt_union = ( *begin )->second.first;
293 for( Iterator i = begin; i != end; ++i )
294 {
295 const Bounding_box& box = ( *i )->second.first;
296 ct::update_bounding_box( elt_union, box );
297 for( std::size_t dim = 0; dim < NUM_DIM; ++dim )
298 {
299 const std::size_t index = bucket_index( box, interval, dim );
300 _bvh::_Bucket& bucket = buckets[dim][index];
301 if( !box_contains_box( bucket.bounding_box, box ) )
302 {
303 std::cerr << "Buckets not covering elements!" << std::endl;
304 }
305 }
306 }
307 if( !box_contains_box( elt_union, interval ) )
308 {
309 std::cout << "element union: " << std::endl << elt_union;
310 std::cout << "intervals: " << std::endl << interval;
311 std::cout << "union of elts does not contain original box!" << std::endl;
312 }
313 if( !box_contains_box( interval, elt_union ) )
314 {
315 std::cout << "original box does not contain union of elts" << std::endl;
316 std::cout << interval << std::endl;
317 std::cout << elt_union << std::endl;
318 }
319 typedef typename Buckets::value_type Bucket_list;
320 typedef typename Bucket_list::const_iterator Bucket_iterator;
321 for( std::size_t d = 0; d < NUM_DIM; ++d )
322 {
323 std::vector< std::size_t > nonempty;
324 const Bucket_list& buckets_ = buckets[d];
325 std::size_t j = 0;
326 for( Bucket_iterator i = buckets_.begin(); i != buckets_.end(); ++i, ++j )
327 {
328 if( i->size > 0 )
329 {
330 nonempty.push_back( j );
331 }
332 }
333 Bounding_box test_box = buckets_[nonempty.front()].bounding_box;
334 for( std::size_t i = 0; i < nonempty.size(); ++i )
335 {
336 ct::update_bounding_box( test_box, buckets_[nonempty[i]].bounding_box );
337 }
338 if( !box_contains_box( test_box, interval ) )
339 {
340 std::cout << "union of buckets in dimension: " << d << "does not contain original box!" << std::endl;
341 }
342 if( !box_contains_box( interval, test_box ) )
343 {
344 std::cout << "original box does "
345 << "not contain union of buckets"
346 << "in dimension: " << d << std::endl;
347 std::cout << interval << std::endl;
348 std::cout << test_box << std::endl;
349 }
350 }
351 #endif
352 }
353
354 template < typename Box, typename Iterator >
355 std::size_t set_interval( Box& interval, const Iterator begin, const Iterator end ) const
356 {
357 bool first = true;
358 std::size_t count = 0;
359 for( Iterator b = begin; b != end; ++b )
360 {
361 const Box& box = b->bounding_box;
362 count += b->size;
363 if( b->size != 0 )
364 {
365 if( first )
366 {
367 interval = box;
368 first = false;
369 }
370 else
371 {
372 ct::update_bounding_box( interval, box );
373 }
374 }
375 }
376 return count;
377 }
378
379 template < typename Splits, typename Buckets, typename Split_data >
380 void initialize_splits( Splits& splits, const Buckets& buckets, const Split_data& data ) const
381 {
382 typedef typename Buckets::value_type Bucket_list;
383 typedef typename Bucket_list::value_type Bucket;
384 typedef typename Bucket_list::const_iterator Bucket_iterator;
385 typedef typename Splits::value_type Split_list;
386 typedef typename Split_list::value_type Split;
387 typedef typename Split_list::iterator Split_iterator;
388 for( std::size_t d = 0; d < NUM_DIM; ++d )
389 {
390 const Split_iterator splits_begin = splits[d].begin();
391 const Split_iterator splits_end = splits[d].end();
392 const Bucket_iterator left_begin = buckets[d].begin();
393 const Bucket_iterator _end = buckets[d].end();
394 Bucket_iterator left_end = buckets[d].begin() + 1;
395 for( Split_iterator s = splits_begin; s != splits_end; ++s, ++left_end )
396 {
397 s->nl = set_interval( s->left_box, left_begin, left_end );
398 if( s->nl == 0 )
399 {
400 s->left_box = data.bounding_box;
401 s->left_box.max[d] = s->left_box.min[d];
402 }
403 s->nr = set_interval( s->right_box, left_end, _end );
404 if( s->nr == 0 )
405 {
406 s->right_box = data.bounding_box;
407 s->right_box.min[d] = s->right_box.max[d];
408 }
409 s->Lmax = s->left_box.max[d];
410 s->Rmin = s->right_box.min[d];
411 s->split = std::distance( splits_begin, s );
412 s->dim = d;
413 }
414 #ifdef BVH_TREE_DEBUG
415 for( Split_iterator s = splits_begin; s != splits_end; ++s, ++left_end )
416 {
417 typename Split::Box test_box = s->left_box;
418 ct::update_bounding_box( test_box, s->right_box );
419 if( !box_contains_box( data.bounding_box, test_box ) )
420 {
421 std::cout << "nr: " << s->nr << std::endl;
422 std::cout << "Test box: " << std::endl << test_box;
423 std::cout << "Left box: " << std::endl << s->left_box;
424 std::cout << "Right box: " << std::endl << s->right_box;
425 std::cout << "Interval: " << std::endl << data.bounding_box;
426 std::cout << "Split boxes larger than bb" << std::endl;
427 }
428 if( !box_contains_box( test_box, data.bounding_box ) )
429 {
430 std::cout << "bb larger than union "
431 << "of split boxes" << std::endl;
432 }
433 }
434 #endif
435 }
436 }
437
438 template < typename Iterator, typename Split_data >
439 void order_elements( const Iterator& begin, const Iterator& end, const Split_data& data ) const
440 {
441 typedef typename Iterator::value_type Map_iterator;
442 for( Iterator i = begin; i != end; ++i )
443 {
444 const int index = bucket_index( ( *i )->second.first, data.bounding_box, data.dim );
445 ( *i )->second.second = ( index <= data.split ) ? 0 : 1;
446 }
447 std::sort( begin, end, _bvh::Iterator_comparator< Map_iterator >() );
448 }
449
450 template < typename Iterator, typename Split_data >
451 void median_order( const Iterator& begin, const Iterator& end, Split_data& data ) const
452 {
453 typedef typename Iterator::value_type Map_iterator;
454 for( Iterator i = begin; i != end; ++i )
455 {
456 const double center = compute_box_center( ( *i )->second.first, data.dim );
457 ( *i )->second.second = center;
458 }
459 std::sort( begin, end, _bvh::Iterator_comparator< Map_iterator >() );
460 const std::size_t total = std::distance( begin, end );
461 Iterator middle = begin + ( total / 2 );
462 double middle_center = ( *middle )->second.second;
463 middle_center += ( *( ++middle ) )->second.second;
464 middle_center /= 2.0;
465 data.split = middle_center;
466 data.nl = std::distance( begin, middle ) + 1;
467 data.nr = total - data.nl;
468 middle++;
469 data.left_box = ( *begin )->second.first;
470 data.right_box = ( *middle )->second.first;
471 for( Iterator i = begin; i != middle; ++i )
472 {
473 ( *i )->second.second = 0;
474 update_bounding_box( data.left_box, ( *i )->second.first );
475 }
476 for( Iterator i = middle; i != end; ++i )
477 {
478 ( *i )->second.second = 1;
479 update_bounding_box( data.right_box, ( *i )->second.first );
480 }
481 data.Rmin = data.right_box.min[data.dim];
482 data.Lmax = data.left_box.max[data.dim];
483 #ifdef BVH_TREE_DEBUG
484 typename Split_data::Box test_box = data.left_box;
485 ct::update_bounding_box( test_box, data.right_box );
486 if( !box_contains_box( data.bounding_box, test_box ) )
487 {
488 std::cerr << "MEDIAN: BB Does not contain splits" << std::endl;
489 }
490 if( !box_contains_box( test_box, data.bounding_box ) )
491 {
492 std::cerr << "MEDIAN: splits do not contain BB" << std::endl;
493 }
494 #endif
495 }
496
497 template < typename Splits, typename Split_data >
498 void choose_best_split( const Splits& splits, Split_data& data ) const
499 {
500 typedef typename Splits::const_iterator List_iterator;
501 typedef typename List_iterator::value_type::const_iterator Split_iterator;
502 typedef typename Split_iterator::value_type Split;
503 std::vector< Split > best_splits;
504 typedef typename _bvh::Split_comparator< Split > Comparator;
505 Comparator compare;
506 for( List_iterator i = splits.begin(); i != splits.end(); ++i )
507 {
508 Split_iterator j = std::min_element( i->begin(), i->end(), compare );
509 best_splits.push_back( *j );
510 }
511 data = *std::min_element( best_splits.begin(), best_splits.end(), compare );
512 }
513
514 template < typename Iterator, typename Split_data >
515 void find_split( const Iterator& begin, const Iterator& end, Split_data& data ) const
516 {
517 typedef typename Iterator::value_type Map_iterator;
518 typedef typename Map_iterator::value_type::second_type Box_data;
519 typedef typename Box_data::first_type _Bounding_box; // Note, not global typedef moab::common_tree::Box<
520 // double> Bounding_box;
521 typedef typename std::vector< Split_data > Split_list;
522 typedef typename std::vector< Split_list > Splits;
523 typedef typename Splits::iterator Split_iterator;
524 typedef typename std::vector< _bvh::_Bucket > Bucket_list;
525 typedef typename std::vector< Bucket_list > Buckets;
526 Buckets buckets( NUM_DIM, Bucket_list( NUM_BUCKETS ) );
527 Splits splits( NUM_DIM, Split_list( NUM_SPLITS, data ) );
528
529 const _Bounding_box interval = data.bounding_box;
530 establish_buckets( begin, end, interval, buckets );
531 initialize_splits( splits, buckets, data );
532 choose_best_split( splits, data );
533 const bool use_median = ( 0 == data.nl ) || ( data.nr == 0 );
534 if( !use_median )
535 {
536 order_elements( begin, end, data );
537 }
538 else
539 {
540 median_order( begin, end, data );
541 }
542 #ifdef BVH_TREE_DEBUG
543 bool seen_one = false, issue = false;
544 bool first_left = true, first_right = true;
545 std::size_t count_left = 0, count_right = 0;
546 typename Split_data::Box left_box, right_box;
547 for( Iterator i = begin; i != end; ++i )
548 {
549 double order = ( *i )->second.second;
550 if( order != 0 && order != 1 )
551 {
552 std::cerr << "Invalid order element !";
553 std::cerr << order << std::endl;
554 std::exit( -1 );
555 }
556 if( order == 1 )
557 {
558 seen_one = 1;
559 count_right++;
560 if( first_right )
561 {
562 right_box = ( *i )->second.first;
563 first_right = false;
564 }
565 else
566 {
567 ct::update_bounding_box( right_box, ( *i )->second.first );
568 }
569 if( !box_contains_box( data.right_box, ( *i )->second.first ) )
570 {
571 if( !issue )
572 {
573 std::cerr << "Bounding right box issue!" << std::endl;
574 }
575 issue = true;
576 }
577 }
578 if( order == 0 )
579 {
580 count_left++;
581 if( first_left )
582 {
583 left_box = ( *i )->second.first;
584 first_left = false;
585 }
586 else
587 {
588 ct::update_bounding_box( left_box, ( *i )->second.first );
589 }
590 if( !box_contains_box( data.left_box, ( *i )->second.first ) )
591 {
592 if( !issue )
593 {
594 std::cerr << "Bounding left box issue!" << std::endl;
595 }
596 issue = true;
597 }
598 if( seen_one )
599 {
600 std::cerr << "Invalid ordering!" << std::endl;
601 std::cout << ( *( i - 1 ) )->second.second << order << std::endl;
602 exit( -1 );
603 }
604 }
605 }
606 if( !box_contains_box( left_box, data.left_box ) )
607 {
608 std::cout << "left elts do not contain left box" << std::endl;
609 }
610 if( !box_contains_box( data.left_box, left_box ) )
611 {
612 std::cout << "left box does not contain left elts" << std::endl;
613 }
614 if( !box_contains_box( right_box, data.right_box ) )
615 {
616 std::cout << "right elts do not contain right box" << std::endl;
617 }
618 if( !box_contains_box( data.right_box, right_box ) )
619 {
620 std::cout << "right box do not contain right elts" << std::endl;
621 }
622 if( count_left != data.nl || count_right != data.nr )
623 {
624 std::cerr << "counts are off!" << std::endl;
625 std::cerr << "total: " << std::distance( begin, end ) << std::endl;
626 std::cerr << "Dim: " << data.dim << std::endl;
627 std::cerr << data.Lmax << " , " << data.Rmin << std::endl;
628 std::cerr << "Right box: " << std::endl << data.right_box << "Left box: " << std::endl << data.left_box;
629 std::cerr << "supposed to be: " << data.nl << " " << data.nr << std::endl;
630 std::cerr << "accountant says: " << count_left << " " << count_right << std::endl;
631 std::exit( -1 );
632 }
633 #endif
634 }
635
636 // private functionality
637 private:
638 template < typename Iterator >
639 int build_tree( const Iterator begin, const Iterator end, const int index, const Box& box, const int depth = 0 )
640 {
641 #ifdef BVH_TREE_DEBUG
642 for( Iterator i = begin; i != end; ++i )
643 {
644 if( !box_contains_box( box, ( *i )->second.first, 0 ) )
645 {
646 std::cerr << "depth: " << depth << std::endl;
647 std::cerr << "BB:" << box << "EB:" << ( *i )->second.first << std::endl;
648 std::exit( -1 );
649 }
650 }
651 #endif
652
653 const std::size_t total_num_elements = std::distance( begin, end );
654 Node& node = tree_[index];
655 // logic for splitting conditions
656 if( total_num_elements > SMAX )
657 {
658 _bvh::_Split_data data;
659 data.bounding_box = box;
660 find_split( begin, end, data );
661 // assign data to node
662 node.Lmax = data.Lmax;
663 node.Rmin = data.Rmin;
664 node.dim = data.dim;
665 node.child = tree_.size();
666 // insert left, right children;
667 tree_.push_back( Node() );
668 tree_.push_back( Node() );
669 const int left_depth = build_tree( begin, begin + data.nl, node.child, data.left_box, depth + 1 );
670 const int right_depth = build_tree( begin + data.nl, end, node.child + 1, data.right_box, depth + 1 );
671 return std::max( left_depth, right_depth );
672 }
673 node.dim = 3;
674 ct::assign_entities( node.entities, begin, end );
675 return depth;
676 }
677
678 template < typename Vector, typename Node_index, typename Result >
679 Result& _find_point( const Vector& point, const Node_index& index, const double tol, Result& result ) const
680 {
681 typedef typename Node::Entities::const_iterator Entity_iterator;
682 const Node& node = tree_[index];
683 if( node.dim == 3 )
684 {
685 for( Entity_iterator i = node.entities.begin(); i != node.entities.end(); ++i )
686 {
687 if( ct::box_contains_point( i->first, point, tol ) )
688 {
689 const std::pair< bool, Vector > r = entity_contains( moab, i->second, point );
690 if( r.first )
691 {
692 return result = std::make_pair( i->second, r.second );
693 }
694 }
695 }
696 result = Result( 0, point );
697 return result;
698 }
699 // the extra tol here considers the case where
700 // 0 < Rmin - Lmax < 2tol
701 if( ( node.Lmax + tol ) < ( node.Rmin - tol ) )
702 {
703 if( point[node.dim] <= ( node.Lmax + tol ) )
704 {
705 return _find_point( point, node.child, tol, result );
706 }
707 else if( point[node.dim] >= ( node.Rmin - tol ) )
708 {
709 return _find_point( point, node.child + 1, tol, result );
710 }
711 result = Result( 0, point );
712 return result; // point lies in empty space.
713 }
714 // Boxes overlap
715 // left of Rmin, you must be on the left
716 // we can't be sure about the boundaries since the boxes overlap
717 // this was a typo in the paper which caused pain.
718 if( point[node.dim] < ( node.Rmin - tol ) )
719 {
720 return _find_point( point, node.child, tol, result );
721 // if you are on the right Lmax, you must be on the right
722 }
723 else if( point[node.dim] > ( node.Lmax + tol ) )
724 {
725 return _find_point( point, node.child + 1, tol, result );
726 }
727 /* pg5 of paper
728 * However, instead of always traversing either subtree
729 * first (e.g. left always before right), we first traverse
730 * the subtree whose bounding plane has the larger distance to the
731 * sought point. This results in less overall traversal, and the correct
732 * cell is identified more quickly.
733 */
734 // Sofar all testing confirms that this 'heuristic' is
735 // significantly slower.
736 // I conjecture this is because it gets improperly
737 // branch predicted..
738 // bool dir = (point[ node.dim] - node.Rmin) <=
739 // (node.Lmax - point[ node.dim]);
740 bool dir = false;
741 _find_point( point, node.child + dir, tol, result );
742 if( result.first == 0 )
743 {
744 return _find_point( point, node.child + ( !dir ), tol, result );
745 }
746 return result;
747 }
748
749 // public functionality
750 public:
751 template < typename Vector, typename Result >
752 Result& find( const Vector& point, const double tol, Result& result ) const
753 {
754 typedef typename Vector::const_iterator Point_iterator;
755 return _find_point( point, 0, tol, result );
756 }
757
758 // public functionality
759 public:
760 template < typename Vector >
761 Entity_handle bruteforce_find( const Vector& point, const double tol ) const
762 {
763 typedef typename Vector::const_iterator Point_iterator;
764 typedef typename Nodes::value_type Node;
765 typedef typename Nodes::const_iterator Node_iterator;
766 typedef typename Node::Entities::const_iterator Entity_iterator;
767 for( Node_iterator i = tree_.begin(); i != tree_.end(); ++i )
768 {
769 if( i->dim == 3 )
770 {
771 for( Entity_iterator j = i->entities.begin(); j != i->entities.end(); ++j )
772 {
773 if( ct::box_contains_point( j->first, point, tol ) )
774 {
775 const std::pair< bool, Vector > result = entity_contains( moab, j->second, point );
776 if( result.first )
777 {
778 return j->second;
779 }
780 }
781 }
782 }
783 }
784 return 0;
785 }
786
787 // public accessor methods
788 public:
789 // private data members
790 private:
791 const Entity_handles& entity_handles_;
792 Nodes tree_;
793 Moab& moab;
794 Box bounding_box;
795 Parametrizer& entity_contains;
796
797 }; // class Bvh_tree
798
799 } // namespace moab
800
801 #endif // BVH_TREE_HPP
1.9.1.