normal_space.hpp

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#ifndef PCL_FILTERS_IMPL_NORMAL_SPACE_SAMPLE_H_
#define PCL_FILTERS_IMPL_NORMAL_SPACE_SAMPLE_H_

#include <pcl/filters/normal_space.h>
#include <pcl/common/io.h>

#include <vector>
#include <list>

template<typename PointT, typename NormalT> bool
pcl::NormalSpaceSampling<PointT, NormalT>::initCompute ()
{
  if (!FilterIndices<PointT>::initCompute ())
    return false;

  // If sample size is 0 or if the sample size is greater then input cloud size then return entire copy of cloud
  if (sample_ >= input_->size ())
  {
    PCL_ERROR ("[NormalSpaceSampling::initCompute] Requested more samples than the input cloud size: %d vs %zu\n",
               sample_, input_->size ());
    return false;
  }

  boost::mt19937 rng (static_cast<unsigned int> (seed_));
  boost::uniform_int<unsigned int> uniform_distrib (0, unsigned (input_->size ()));
  if (rng_uniform_distribution_ != NULL)
    delete rng_uniform_distribution_;
  rng_uniform_distribution_ = new boost::variate_generator<boost::mt19937, boost::uniform_int<unsigned int> > (rng, uniform_distrib);

  return (true);
}

template<typename PointT, typename NormalT> void
pcl::NormalSpaceSampling<PointT, NormalT>::applyFilter (PointCloud &output)
{
  std::vector<int> indices;
  if (keep_organized_)
  {
    bool temp = extract_removed_indices_;
    extract_removed_indices_ = true;
    applyFilter (indices);
    extract_removed_indices_ = temp;

    output = *input_;
    for (int rii = 0; rii < static_cast<int> (removed_indices_->size ()); ++rii)  // rii = removed indices iterator
      output.points[(*removed_indices_)[rii]].x = output.points[(*removed_indices_)[rii]].y = output.points[(*removed_indices_)[rii]].z = user_filter_value_;
    if (!pcl_isfinite (user_filter_value_))
      output.is_dense = false;
  }
  else
  {
    output.is_dense = true;
    applyFilter (indices);
    pcl::copyPointCloud (*input_, indices, output);
  }
}

template<typename PointT, typename NormalT> bool 
pcl::NormalSpaceSampling<PointT, NormalT>::isEntireBinSampled (boost::dynamic_bitset<> &array,
                                                               unsigned int start_index,
                                                               unsigned int length)
{
  bool status = true;
  for (unsigned int i = start_index; i < start_index + length; i++)
  {
    status = status & array.test (i);
  }
  return status;
}

template<typename PointT, typename NormalT> unsigned int 
pcl::NormalSpaceSampling<PointT, NormalT>::findBin (const float *normal, unsigned int)
{
  unsigned int bin_number = 0;
  // Holds the bin numbers for direction cosines in x,y,z directions
  unsigned int t[3] = {0,0,0};
  
  // dcos is the direction cosine.
  float dcos = 0.0;
  float bin_size = 0.0;
  // max_cos and min_cos are the maximum and minimum values of cos(theta) respectively
  float max_cos = 1.0;
  float min_cos = -1.0;

//  dcos = cosf (normal[0]);
  dcos = normal[0];
  bin_size = (max_cos - min_cos) / static_cast<float> (binsx_);

  // Finding bin number for direction cosine in x direction
  unsigned int k = 0;
  for (float i = min_cos; (i + bin_size) < (max_cos - bin_size); i += bin_size , k++)
  {
    if (dcos >= i && dcos <= (i+bin_size))
    {
      break;
    }
  }
  t[0] = k;

//  dcos = cosf (normal[1]);
  dcos = normal[1];
  bin_size = (max_cos - min_cos) / static_cast<float> (binsy_);

  // Finding bin number for direction cosine in y direction
  k = 0;
  for (float i = min_cos; (i + bin_size) < (max_cos - bin_size); i += bin_size , k++)
  {
    if (dcos >= i && dcos <= (i+bin_size))
    {
      break;
    }
  }
  t[1] = k;
    
//  dcos = cosf (normal[2]);
  dcos = normal[2];
  bin_size = (max_cos - min_cos) / static_cast<float> (binsz_);

  // Finding bin number for direction cosine in z direction
  k = 0;
  for (float i = min_cos; (i + bin_size) < (max_cos - bin_size); i += bin_size , k++)
  {
    if (dcos >= i && dcos <= (i+bin_size))
    {
      break;
    }
  }
  t[2] = k;

  bin_number = t[0] * (binsy_*binsz_) + t[1] * binsz_ + t[2];
  return bin_number;
}

template<typename PointT, typename NormalT> void
pcl::NormalSpaceSampling<PointT, NormalT>::applyFilter (std::vector<int> &indices)
{
  if (!initCompute ())
  {
    indices = *indices_;
    return;
  }

  unsigned int max_values = (std::min) (sample_, static_cast<unsigned int> (input_normals_->size ()));
  // Resize output indices to sample size
  indices.resize (max_values);
  removed_indices_->resize (max_values);
  
  // Allocate memory for the histogram of normals. Normals will then be sampled from each bin.
  unsigned int n_bins = binsx_ * binsy_ * binsz_;
  // list<int> holds the indices of points in that bin. Using list to avoid repeated resizing of vectors.
  // Helps when the point cloud is large.
  std::vector<std::list <int> > normals_hg;
  normals_hg.reserve (n_bins);
  for (unsigned int i = 0; i < n_bins; i++)
    normals_hg.push_back (std::list<int> ());

  for (std::vector<int>::const_iterator it = indices_->begin (); it != indices_->end (); ++it)
  {
    unsigned int bin_number = findBin (input_normals_->points[*it].normal, n_bins);
    normals_hg[bin_number].push_back (*it);
  }


  // Setting up random access for the list created above. Maintaining the iterators to individual elements of the list
  // in a vector. Using vector now as the size of the list is known.
  std::vector<std::vector<std::list<int>::iterator> > random_access (normals_hg.size ());
  for (unsigned int i = 0; i < normals_hg.size (); i++)
  {
    random_access.push_back (std::vector<std::list<int>::iterator> ());
    random_access[i].resize (normals_hg[i].size ());

    unsigned int j = 0;
    for (std::list<int>::iterator itr = normals_hg[i].begin (); itr != normals_hg[i].end (); itr++, j++)
      random_access[i][j] = itr;
  }
  std::vector<unsigned int> start_index (normals_hg.size ());
  start_index[0] = 0;
  unsigned int prev_index = start_index[0];
  for (unsigned int i = 1; i < normals_hg.size (); i++)
  {
    start_index[i] = prev_index + static_cast<unsigned int> (normals_hg[i-1].size ());
    prev_index = start_index[i];
  }

  // Maintaining flags to check if a point is sampled
  boost::dynamic_bitset<> is_sampled_flag (input_normals_->points.size ());
  // Maintaining flags to check if all points in the bin are sampled
  boost::dynamic_bitset<> bin_empty_flag (normals_hg.size ());
  unsigned int i = 0;
  while (i < sample_)
  {
    // Iterating through every bin and picking one point at random, until the required number of points are sampled.
    for (unsigned int j = 0; j < normals_hg.size (); j++)
    {
      unsigned int M = static_cast<unsigned int> (normals_hg[j].size ());
      if (M == 0 || bin_empty_flag.test (j)) // bin_empty_flag(i) is set if all points in that bin are sampled..
        continue;

      unsigned int pos = 0;
      unsigned int random_index = 0;

      // Picking up a sample at random from jth bin
      do
      {
        random_index = static_cast<unsigned int> ((*rng_uniform_distribution_) () % M);
        pos = start_index[j] + random_index;
      } while (is_sampled_flag.test (pos));

      is_sampled_flag.flip (start_index[j] + random_index);

      // Checking if all points in bin j are sampled.
      if (isEntireBinSampled (is_sampled_flag, start_index[j], static_cast<unsigned int> (normals_hg[j].size ()))) 
        bin_empty_flag.flip (j);

      unsigned int index = *(random_access[j][random_index]);
      indices[i] = index;
      i++;
      if (i == sample_)
        break;
    }
  }
  
  // If we need to return the indices that we haven't sampled
  if (extract_removed_indices_)
  {
    std::vector<int> indices_temp = indices;
    std::sort (indices_temp.begin (), indices_temp.end ());

    std::vector<int> all_indices_temp = *indices_;
    std::sort (all_indices_temp.begin (), all_indices_temp.end ());
    set_difference (all_indices_temp.begin (), all_indices_temp.end (), 
                    indices_temp.begin (), indices_temp.end (), 
                    inserter (*removed_indices_, removed_indices_->begin ()));
  }
}

#define PCL_INSTANTIATE_NormalSpaceSampling(T,NT) template class PCL_EXPORTS pcl::NormalSpaceSampling<T,NT>;

#endif    // PCL_FILTERS_IMPL_NORMAL_SPACE_SAMPLE_H_