Point Cloud Library (PCL)  1.13.1-dev
lccp_segmentation.hpp
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37 
38 #ifndef PCL_SEGMENTATION_IMPL_LCCP_SEGMENTATION_HPP_
39 #define PCL_SEGMENTATION_IMPL_LCCP_SEGMENTATION_HPP_
40 
41 #include <pcl/segmentation/lccp_segmentation.h>
42 #include <pcl/common/common.h>
43 
44 
45 //////////////////////////////////////////////////////////
46 //////////////////////////////////////////////////////////
47 /////////////////// Public Functions /////////////////////
48 //////////////////////////////////////////////////////////
49 //////////////////////////////////////////////////////////
50 
51 
52 
53 template <typename PointT>
55  concavity_tolerance_threshold_ (10),
56  grouping_data_valid_ (false),
57  supervoxels_set_ (false),
58  use_smoothness_check_ (false),
59  smoothness_threshold_ (0.1),
60  use_sanity_check_ (false),
61  seed_resolution_ (0),
62  voxel_resolution_ (0),
63  k_factor_ (0),
64  min_segment_size_ (0)
65 {
66 }
67 
68 template <typename PointT>
70 
71 template <typename PointT> void
73 {
74  sv_adjacency_list_.clear ();
75  processed_.clear ();
76  sv_label_to_supervoxel_map_.clear ();
77  sv_label_to_seg_label_map_.clear ();
78  seg_label_to_sv_list_map_.clear ();
79  seg_label_to_neighbor_set_map_.clear ();
80  grouping_data_valid_ = false;
81  supervoxels_set_ = false;
82 }
83 
84 template <typename PointT> void
86 {
87  if (supervoxels_set_)
88  {
89  // Calculate for every Edge if the connection is convex or invalid
90  // This effectively performs the segmentation.
91  calculateConvexConnections (sv_adjacency_list_);
92 
93  // Correct edge relations using extended convexity definition if k>0
94  applyKconvexity (k_factor_);
95 
96  // group supervoxels
97  doGrouping ();
98 
99  grouping_data_valid_ = true;
100 
101  // merge small segments
102  mergeSmallSegments ();
103  }
104  else
105  PCL_WARN ("[pcl::LCCPSegmentation::segment] WARNING: Call function setInputSupervoxels first. Nothing has been done. \n");
106 }
107 
108 
109 template <typename PointT> void
111 {
112  if (grouping_data_valid_)
113  {
114  // Relabel all Points in cloud with new labels
115  for (auto &voxel : labeled_cloud_arg)
116  {
117  voxel.label = sv_label_to_seg_label_map_[voxel.label];
118  }
119  }
120  else
121  {
122  PCL_WARN ("[pcl::LCCPSegmentation::relabelCloud] WARNING: Call function segment first. Nothing has been done. \n");
123  }
124 }
125 
126 
127 
128 //////////////////////////////////////////////////////////
129 //////////////////////////////////////////////////////////
130 /////////////////// Protected Functions //////////////////
131 //////////////////////////////////////////////////////////
132 //////////////////////////////////////////////////////////
133 
134 template <typename PointT> void
136 {
137  seg_label_to_neighbor_set_map_.clear ();
138 
139  std::uint32_t current_segLabel;
140  std::uint32_t neigh_segLabel;
141 
142  VertexIterator sv_itr, sv_itr_end;
143  //The vertices in the supervoxel adjacency list are the supervoxel centroids
144  // For every Supervoxel..
145  for(std::tie(sv_itr, sv_itr_end) = boost::vertices(sv_adjacency_list_); sv_itr != sv_itr_end; ++sv_itr) // For all supervoxels
146  {
147  const std::uint32_t& sv_label = sv_adjacency_list_[*sv_itr];
148  current_segLabel = sv_label_to_seg_label_map_[sv_label];
149 
150  AdjacencyIterator itr_neighbor, itr_neighbor_end;
151  // ..look at all neighbors and insert their labels into the neighbor set
152  for (std::tie(itr_neighbor, itr_neighbor_end) = boost::adjacent_vertices (*sv_itr, sv_adjacency_list_); itr_neighbor != itr_neighbor_end; ++itr_neighbor)
153  {
154  const std::uint32_t& neigh_label = sv_adjacency_list_[*itr_neighbor];
155  neigh_segLabel = sv_label_to_seg_label_map_[neigh_label];
156 
157  if (current_segLabel != neigh_segLabel)
158  {
159  seg_label_to_neighbor_set_map_[current_segLabel].insert (neigh_segLabel);
160  }
161  }
162  }
163 }
164 
165 template <typename PointT> void
167 {
168  if (min_segment_size_ == 0)
169  return;
170 
171  computeSegmentAdjacency ();
172 
173  std::set<std::uint32_t> filteredSegLabels;
174 
175  bool continue_filtering = true;
176 
177  while (continue_filtering)
178  {
179  continue_filtering = false;
180 
181  VertexIterator sv_itr, sv_itr_end;
182  // Iterate through all supervoxels, check if they are in a "small" segment -> change label to largest neighborID
183  for (std::tie(sv_itr, sv_itr_end) = boost::vertices (sv_adjacency_list_); sv_itr != sv_itr_end; ++sv_itr) // For all supervoxels
184  {
185  const std::uint32_t& sv_label = sv_adjacency_list_[*sv_itr];
186  std::uint32_t current_seg_label = sv_label_to_seg_label_map_[sv_label];
187  std::uint32_t largest_neigh_seg_label = current_seg_label;
188  std::uint32_t largest_neigh_size = seg_label_to_sv_list_map_[current_seg_label].size ();
189 
190  const std::uint32_t& nr_neighbors = seg_label_to_neighbor_set_map_[current_seg_label].size ();
191  if (nr_neighbors == 0)
192  continue;
193 
194  if (seg_label_to_sv_list_map_[current_seg_label].size () <= min_segment_size_)
195  {
196  continue_filtering = true;
197 
198  // Find largest neighbor
199  for (auto neighbors_itr = seg_label_to_neighbor_set_map_[current_seg_label].cbegin (); neighbors_itr != seg_label_to_neighbor_set_map_[current_seg_label].cend (); ++neighbors_itr)
200  {
201  if (seg_label_to_sv_list_map_[*neighbors_itr].size () >= largest_neigh_size)
202  {
203  largest_neigh_seg_label = *neighbors_itr;
204  largest_neigh_size = seg_label_to_sv_list_map_[*neighbors_itr].size ();
205  }
206  }
207 
208  // Add to largest neighbor
209  if (largest_neigh_seg_label != current_seg_label)
210  {
211  if (filteredSegLabels.count (largest_neigh_seg_label) > 0)
212  continue; // If neighbor was already assigned to someone else
213 
214  sv_label_to_seg_label_map_[sv_label] = largest_neigh_seg_label;
215  filteredSegLabels.insert (current_seg_label);
216 
217  // Assign supervoxel labels of filtered segment to new owner
218  for (auto sv_ID_itr = seg_label_to_sv_list_map_[current_seg_label].cbegin (); sv_ID_itr != seg_label_to_sv_list_map_[current_seg_label].cend (); ++sv_ID_itr)
219  {
220  seg_label_to_sv_list_map_[largest_neigh_seg_label].insert (*sv_ID_itr);
221  }
222  }
223  }
224  }
225 
226  // Erase filtered Segments from segment map
227  for (const unsigned int &filteredSegLabel : filteredSegLabels)
228  {
229  seg_label_to_sv_list_map_.erase (filteredSegLabel);
230  }
231 
232  // After filtered Segments are deleted, compute completely new adjacency map
233  // NOTE Recomputing the adjacency of every segment in every iteration is an easy but inefficient solution.
234  // Because the number of segments in an average scene is usually well below 1000, the time spend for noise filtering is still negligible in most cases
235  computeSegmentAdjacency ();
236  } // End while (Filtering)
237 }
238 
239 template <typename PointT> void
240 pcl::LCCPSegmentation<PointT>::prepareSegmentation (const std::map<std::uint32_t, typename pcl::Supervoxel<PointT>::Ptr>& supervoxel_clusters_arg,
241  const std::multimap<std::uint32_t, std::uint32_t>& label_adjaceny_arg)
242 {
243  // Clear internal data
244  reset ();
245 
246  // Copy map with supervoxel pointers
247  sv_label_to_supervoxel_map_ = supervoxel_clusters_arg;
248 
249  // Build a boost adjacency list from the adjacency multimap
250  std::map<std::uint32_t, VertexID> label_ID_map;
251 
252  // Add all supervoxel labels as vertices
253  for (auto svlabel_itr = sv_label_to_supervoxel_map_.begin ();
254  svlabel_itr != sv_label_to_supervoxel_map_.end (); ++svlabel_itr)
255  {
256  const std::uint32_t& sv_label = svlabel_itr->first;
257  VertexID node_id = boost::add_vertex (sv_adjacency_list_);
258  sv_adjacency_list_[node_id] = sv_label;
259  label_ID_map[sv_label] = node_id;
260  }
261 
262  // Add all edges
263  for (const auto &sv_neighbors_itr : label_adjaceny_arg)
264  {
265  const std::uint32_t& sv_label = sv_neighbors_itr.first;
266  const std::uint32_t& neighbor_label = sv_neighbors_itr.second;
267 
268  VertexID u = label_ID_map[sv_label];
269  VertexID v = label_ID_map[neighbor_label];
270 
271  boost::add_edge (u, v, sv_adjacency_list_);
272  }
273 
274  // Initialization
275  // clear the processed_ map
276  seg_label_to_sv_list_map_.clear ();
277  for (auto svlabel_itr = sv_label_to_supervoxel_map_.begin ();
278  svlabel_itr != sv_label_to_supervoxel_map_.end (); ++svlabel_itr)
279  {
280  const std::uint32_t& sv_label = svlabel_itr->first;
281  processed_[sv_label] = false;
282  sv_label_to_seg_label_map_[sv_label] = 0;
283  }
284 }
285 
286 
287 
288 
289 template <typename PointT> void
291 {
292  // clear the processed_ map
293  seg_label_to_sv_list_map_.clear ();
294  for (auto svlabel_itr = sv_label_to_supervoxel_map_.begin ();
295  svlabel_itr != sv_label_to_supervoxel_map_.end (); ++svlabel_itr)
296  {
297  const std::uint32_t& sv_label = svlabel_itr->first;
298  processed_[sv_label] = false;
299  sv_label_to_seg_label_map_[sv_label] = 0;
300  }
301 
302  VertexIterator sv_itr, sv_itr_end;
303  // Perform depth search on the graph and recursively group all supervoxels with convex connections
304  //The vertices in the supervoxel adjacency list are the supervoxel centroids
305  // Note: *sv_itr is of type " boost::graph_traits<VoxelAdjacencyList>::vertex_descriptor " which it nothing but a typedef of std::size_t..
306  unsigned int segment_label = 1; // This starts at 1, because 0 is reserved for errors
307  for (std::tie(sv_itr, sv_itr_end) = boost::vertices (sv_adjacency_list_); sv_itr != sv_itr_end; ++sv_itr) // For all supervoxels
308  {
309  const VertexID sv_vertex_id = *sv_itr;
310  const std::uint32_t& sv_label = sv_adjacency_list_[sv_vertex_id];
311  if (!processed_[sv_label])
312  {
313  // Add neighbors (and their neighbors etc.) to group if similarity constraint is met
314  recursiveSegmentGrowing (sv_vertex_id, segment_label);
315  ++segment_label; // After recursive grouping ended (no more neighbors to consider) -> go to next group
316  }
317  }
318 }
319 
320 template <typename PointT> void
322  const unsigned int segment_label)
323 {
324  const std::uint32_t& sv_label = sv_adjacency_list_[query_point_id];
325 
326  processed_[sv_label] = true;
327 
328  // The next two lines add the supervoxel to the segment
329  sv_label_to_seg_label_map_[sv_label] = segment_label;
330  seg_label_to_sv_list_map_[segment_label].insert (sv_label);
331 
332  OutEdgeIterator out_Edge_itr, out_Edge_itr_end;
333  // Iterate through all neighbors of this supervoxel and check whether they should be merged with the current supervoxel
334  // boost::out_edges (query_point_id, sv_adjacency_list_): adjacent vertices to node (*itr) in graph sv_adjacency_list_
335  for (std::tie(out_Edge_itr, out_Edge_itr_end) = boost::out_edges (query_point_id, sv_adjacency_list_); out_Edge_itr != out_Edge_itr_end; ++out_Edge_itr)
336  {
337  const VertexID neighbor_ID = boost::target (*out_Edge_itr, sv_adjacency_list_);
338  const std::uint32_t& neighbor_label = sv_adjacency_list_[neighbor_ID];
339 
340  if (!processed_[neighbor_label]) // If neighbor was not already processed
341  {
342  if (sv_adjacency_list_[*out_Edge_itr].is_valid)
343  {
344  recursiveSegmentGrowing (neighbor_ID, segment_label);
345  }
346  }
347  } // End neighbor loop
348 }
349 
350 template <typename PointT> void
352 {
353  if (k_arg == 0)
354  return;
355 
356  EdgeIterator edge_itr, edge_itr_end, next_edge;
357  // Check all edges in the graph for k-convexity
358  for (std::tie (edge_itr, edge_itr_end) = boost::edges (sv_adjacency_list_), next_edge = edge_itr; edge_itr != edge_itr_end; edge_itr = next_edge)
359  {
360  ++next_edge; // next_edge iterator is necessary, because removing an edge invalidates the iterator to the current edge
361 
362  bool is_convex = sv_adjacency_list_[*edge_itr].is_convex;
363 
364  if (is_convex) // If edge is (0-)convex
365  {
366  unsigned int kcount = 0;
367 
368  const VertexID source = boost::source (*edge_itr, sv_adjacency_list_);
369  const VertexID target = boost::target (*edge_itr, sv_adjacency_list_);
370 
371  OutEdgeIterator source_neighbors_itr, source_neighbors_itr_end;
372  // Find common neighbors, check their connection
373  for (std::tie(source_neighbors_itr, source_neighbors_itr_end) = boost::out_edges (source, sv_adjacency_list_); source_neighbors_itr != source_neighbors_itr_end; ++source_neighbors_itr) // For all supervoxels
374  {
375  VertexID source_neighbor_ID = boost::target (*source_neighbors_itr, sv_adjacency_list_);
376 
377  OutEdgeIterator target_neighbors_itr, target_neighbors_itr_end;
378  for (std::tie(target_neighbors_itr, target_neighbors_itr_end) = boost::out_edges (target, sv_adjacency_list_); target_neighbors_itr != target_neighbors_itr_end; ++target_neighbors_itr) // For all supervoxels
379  {
380  VertexID target_neighbor_ID = boost::target (*target_neighbors_itr, sv_adjacency_list_);
381  if (source_neighbor_ID == target_neighbor_ID) // Common neighbor
382  {
383  EdgeID src_edge = boost::edge (source, source_neighbor_ID, sv_adjacency_list_).first;
384  EdgeID tar_edge = boost::edge (target, source_neighbor_ID, sv_adjacency_list_).first;
385 
386  bool src_is_convex = (sv_adjacency_list_)[src_edge].is_convex;
387  bool tar_is_convex = (sv_adjacency_list_)[tar_edge].is_convex;
388 
389  if (src_is_convex && tar_is_convex)
390  ++kcount;
391 
392  break;
393  }
394  }
395 
396  if (kcount >= k_arg) // Connection is k-convex, stop search
397  break;
398  }
399 
400  // Check k convexity
401  if (kcount < k_arg)
402  (sv_adjacency_list_)[*edge_itr].is_valid = false;
403  }
404  }
405 }
406 
407 template <typename PointT> void
409 {
410 
411  EdgeIterator edge_itr, edge_itr_end, next_edge;
412  for (std::tie(edge_itr, edge_itr_end) = boost::edges (adjacency_list_arg), next_edge = edge_itr; edge_itr != edge_itr_end; edge_itr = next_edge)
413  {
414  ++next_edge; // next_edge iterator is necessary, because removing an edge invalidates the iterator to the current edge
415 
416  std::uint32_t source_sv_label = adjacency_list_arg[boost::source (*edge_itr, adjacency_list_arg)];
417  std::uint32_t target_sv_label = adjacency_list_arg[boost::target (*edge_itr, adjacency_list_arg)];
418 
419  float normal_difference;
420  bool is_convex = connIsConvex (source_sv_label, target_sv_label, normal_difference);
421  adjacency_list_arg[*edge_itr].is_convex = is_convex;
422  adjacency_list_arg[*edge_itr].is_valid = is_convex;
423  adjacency_list_arg[*edge_itr].normal_difference = normal_difference;
424  }
425 }
426 
427 template <typename PointT> bool
428 pcl::LCCPSegmentation<PointT>::connIsConvex (const std::uint32_t source_label_arg,
429  const std::uint32_t target_label_arg,
430  float &normal_angle)
431 {
432  typename pcl::Supervoxel<PointT>::Ptr& sv_source = sv_label_to_supervoxel_map_[source_label_arg];
433  typename pcl::Supervoxel<PointT>::Ptr& sv_target = sv_label_to_supervoxel_map_[target_label_arg];
434 
435  const Eigen::Vector3f& source_centroid = sv_source->centroid_.getVector3fMap ();
436  const Eigen::Vector3f& target_centroid = sv_target->centroid_.getVector3fMap ();
437 
438  const Eigen::Vector3f& source_normal = sv_source->normal_.getNormalVector3fMap (). normalized ();
439  const Eigen::Vector3f& target_normal = sv_target->normal_.getNormalVector3fMap (). normalized ();
440 
441  //NOTE For angles below 0 nothing will be merged
442  if (concavity_tolerance_threshold_ < 0)
443  {
444  return (false);
445  }
446 
447  bool is_convex = true;
448  bool is_smooth = true;
449 
450  normal_angle = getAngle3D (source_normal, target_normal, true);
451  // Geometric comparisons
452  Eigen::Vector3f vec_t_to_s, vec_s_to_t;
453 
454  vec_t_to_s = source_centroid - target_centroid;
455  vec_s_to_t = -vec_t_to_s;
456 
457  Eigen::Vector3f ncross;
458  ncross = source_normal.cross (target_normal);
459 
460  // Smoothness Check: Check if there is a step between adjacent patches
461  if (use_smoothness_check_)
462  {
463  float expected_distance = ncross.norm () * seed_resolution_;
464  float dot_p_1 = vec_t_to_s.dot (source_normal);
465  float dot_p_2 = vec_s_to_t.dot (target_normal);
466  float point_dist = (std::fabs (dot_p_1) < std::fabs (dot_p_2)) ? std::fabs (dot_p_1) : std::fabs (dot_p_2);
467  const float dist_smoothing = smoothness_threshold_ * voxel_resolution_; // This is a slacking variable especially important for patches with very similar normals
468 
469  if (point_dist > (expected_distance + dist_smoothing))
470  {
471  is_smooth &= false;
472  }
473  }
474  // ----------------
475 
476  // Sanity Criterion: Check if definition convexity/concavity makes sense for connection of given patches
477  float intersection_angle = getAngle3D (ncross, vec_t_to_s, true);
478  float min_intersect_angle = (intersection_angle < 90.) ? intersection_angle : 180. - intersection_angle;
479 
480  float intersect_thresh = 60. * 1. / (1. + std::exp (-0.25 * (normal_angle - 25.)));
481  if (min_intersect_angle < intersect_thresh && use_sanity_check_)
482  {
483  // std::cout << "Concave/Convex not defined for given case!" << std::endl;
484  is_convex &= false;
485  }
486 
487 
488  // vec_t_to_s is the reference direction for angle measurements
489  // Convexity Criterion: Check if connection of patches is convex. If this is the case the two supervoxels should be merged.
490  if ((getAngle3D (vec_t_to_s, source_normal) - getAngle3D (vec_t_to_s, target_normal)) <= 0)
491  {
492  is_convex &= true; // connection convex
493  }
494  else
495  {
496  is_convex &= (normal_angle < concavity_tolerance_threshold_); // concave connections will be accepted if difference of normals is small
497  }
498  return (is_convex && is_smooth);
499 }
500 
501 #endif // PCL_SEGMENTATION_IMPL_LCCP_SEGMENTATION_HPP_
virtual ~LCCPSegmentation()
typename boost::graph_traits< SupervoxelAdjacencyList >::vertex_iterator VertexIterator
typename boost::graph_traits< SupervoxelAdjacencyList >::edge_iterator EdgeIterator
boost::adjacency_list< boost::setS, boost::setS, boost::undirectedS, std::uint32_t, EdgeProperties > SupervoxelAdjacencyList
void recursiveSegmentGrowing(const VertexID &queryPointID, const unsigned int group_label)
Assigns neighbors of the query point to the same group as the query point.
void calculateConvexConnections(SupervoxelAdjacencyList &adjacency_list_arg)
Calculates convexity of edges and saves this to the adjacency graph.
void computeSegmentAdjacency()
Compute the adjacency of the segments.
void relabelCloud(pcl::PointCloud< pcl::PointXYZL > &labeled_cloud_arg)
Relabels cloud with supervoxel labels with the computed segment labels.
void mergeSmallSegments()
Segments smaller than min_segment_size_ are merged to the label of largest neighbor.
void prepareSegmentation(const std::map< std::uint32_t, typename pcl::Supervoxel< PointT >::Ptr > &supervoxel_clusters_arg, const std::multimap< std::uint32_t, std::uint32_t > &label_adjacency_arg)
Is called within setInputSupervoxels mainly to reserve required memory.
void segment()
Merge supervoxels using local convexity.
typename boost::graph_traits< SupervoxelAdjacencyList >::out_edge_iterator OutEdgeIterator
typename boost::graph_traits< SupervoxelAdjacencyList >::adjacency_iterator AdjacencyIterator
bool connIsConvex(const std::uint32_t source_label_arg, const std::uint32_t target_label_arg, float &normal_angle)
Returns true if the connection between source and target is convex.
void doGrouping()
Perform depth search on the graph and recursively group all supervoxels with convex connections.
void applyKconvexity(const unsigned int k_arg)
Connections are only convex if this is true for at least k_arg common neighbors of the two patches.
typename boost::graph_traits< SupervoxelAdjacencyList >::edge_descriptor EdgeID
typename boost::graph_traits< SupervoxelAdjacencyList >::vertex_descriptor VertexID
void reset()
Reset internal memory.
PointCloud represents the base class in PCL for storing collections of 3D points.
Definition: point_cloud.h:173
pcl::PointXYZRGBA centroid_
The centroid of the supervoxel - average voxel.
shared_ptr< Supervoxel< PointT > > Ptr
pcl::Normal normal_
The normal calculated for the voxels contained in the supervoxel.
Define standard C methods and C++ classes that are common to all methods.
double getAngle3D(const Eigen::Vector4f &v1, const Eigen::Vector4f &v2, const bool in_degree=false)
Compute the smallest angle between two 3D vectors in radians (default) or degree.
Definition: common.hpp:47