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 <vector>
#include <list>

template<typename PointT, typename NormalT> void
pcl::NormalSpaceSampling<PointT, NormalT>::applyFilter (PointCloud &output)
{
  // 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 ())
  {
    output = *input_;
    return;
  }

  // Resize output cloud to sample size
  output.points.resize (sample_);
  output.width = sample_;
  output.height = 1;
  
  // 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 (unsigned int i = 0; i < input_normals_->points.size (); i++)
  {
    unsigned int bin_number = findBin (input_normals_->points[i].normal, n_bins);
    normals_hg[bin_number].push_back (i);
  }

  // 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;
    }
  }
  unsigned int* start_index = new unsigned int[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 = std::rand () % 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]);
      output.points[i] = input_->points[index];
      i++;
      if (i == sample_)
      {
        break;
      }
    }
  }
  delete[] start_index;
}

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 (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]);
  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]);
  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]);
  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 sample size is 0 or if the sample size is greater then input cloud size
  //   then return all indices
  if (sample_ >= input_->width * input_->height)
  {
    indices = *indices_;
    return;
  }

  // Resize output indices to sample size
  indices.resize (sample_);
  
  // 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 (unsigned int i=0; i < input_normals_->points.size (); i++)
  {
    unsigned int bin_number = findBin (input_normals_->points[i].normal, n_bins);
    normals_hg[bin_number].push_back (i);
  }

  // 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;
    }
  }
  unsigned int* start_index = new unsigned int[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 = std::rand () % 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;
      }
    }
  }
  delete[] start_index;
}

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

#endif    // PCL_FILTERS_IMPL_NORMAL_SPACE_SAMPLE_H_