crop_hull.hpp

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#ifndef PCL_FILTERS_IMPL_CROP_HULL_H_
#define PCL_FILTERS_IMPL_CROP_HULL_H_

#include <pcl/filters/crop_hull.h>

template<typename PointT> void
pcl::CropHull<PointT>::applyFilter (PointCloud &output)
{
  if (dim_ == 2)
  {
    // in this case we are assuming all the points lie in the same plane as the
    // 2D convex hull, so the choice of projection just changes the
    // conditioning of the problem: choose to squash the XYZ component of the
    // hull-points that has least variation - this will also give reasonable
    // results if the points don't lie exactly in the same plane
    const Eigen::Vector3f range = getHullCloudRange ();
    if (range[0] <= range[1] && range[0] <= range[2])
      applyFilter2D<1,2> (output);
    else if (range[1] <= range[2] && range[1] <= range[0])
      applyFilter2D<2,0> (output);
    else
      applyFilter2D<0,1> (output);
  }
  else
  {
    applyFilter3D (output);
  }
}

template<typename PointT> void
pcl::CropHull<PointT>::applyFilter (std::vector<int> &indices)
{
  if (dim_ == 2)
  {
    // in this case we are assuming all the points lie in the same plane as the
    // 2D convex hull, so the choice of projection just changes the
    // conditioning of the problem: choose to squash the XYZ component of the
    // hull-points that has least variation - this will also give reasonable
    // results if the points don't lie exactly in the same plane
    const Eigen::Vector3f range = getHullCloudRange ();
    if (range[0] <= range[1] && range[0] <= range[2])
      applyFilter2D<1,2> (indices);
    else if (range[1] <= range[2] && range[1] <= range[0])
      applyFilter2D<2,0> (indices);
    else
      applyFilter2D<0,1> (indices);
  }
  else
  {
    applyFilter3D (indices);
  }
}

template<typename PointT> Eigen::Vector3f
pcl::CropHull<PointT>::getHullCloudRange ()
{
  Eigen::Vector3f cloud_min (
    std::numeric_limits<float> ().max (),
    std::numeric_limits<float> ().max (),
    std::numeric_limits<float> ().max ()
  );
  Eigen::Vector3f cloud_max (
    -std::numeric_limits<float> ().max (),
    -std::numeric_limits<float> ().max (),
    -std::numeric_limits<float> ().max ()
  );
  for (size_t index = 0; index < indices_->size (); index++)
  {
    Eigen::Vector3f pt = input_->points[(*indices_)[index]].getVector3fMap ();
    for (int i = 0; i < 3; i++)
    {
      if (pt[i] < cloud_min[i]) cloud_min[i] = pt[i];
      if (pt[i] > cloud_max[i]) cloud_max[i] = pt[i];
    }
  }
  
  return (cloud_max - cloud_min);
}

template<typename PointT> template<unsigned PlaneDim1, unsigned PlaneDim2> void 
pcl::CropHull<PointT>::applyFilter2D (PointCloud &output)
{
  for (size_t index = 0; index < indices_->size (); index++)
  {
    // iterate over polygons faster than points because we expect this data
    // to be, in general, more cache-local - the point cloud might be huge
    size_t poly;
    for (poly = 0; poly < hull_polygons_.size (); poly++)
    {
      if (isPointIn2DPolyWithVertIndices<PlaneDim1,PlaneDim2> (
              input_->points[(*indices_)[index]], hull_polygons_[poly], *hull_cloud_
         ))
      {
        if (crop_outside_)
          output.push_back (input_->points[(*indices_)[index]]);
        // once a point has tested +ve for being inside one polygon, we can
        // stop checking the others:
        break;
      }
    }
    // If we're removing points *inside* the hull, only remove points that
    // haven't been found inside any polygons
    if (poly == hull_polygons_.size () && !crop_outside_)
      output.push_back (input_->points[(*indices_)[index]]);
  }
}

template<typename PointT> template<unsigned PlaneDim1, unsigned PlaneDim2> void 
pcl::CropHull<PointT>::applyFilter2D (std::vector<int> &indices)
{
  // see comments in (PointCloud& output) overload
  for (size_t index = 0; index < indices_->size (); index++)
  {
    size_t poly;
    for (poly = 0; poly < hull_polygons_.size (); poly++)
    {
      if (isPointIn2DPolyWithVertIndices<PlaneDim1,PlaneDim2> (
              input_->points[(*indices_)[index]], hull_polygons_[poly], *hull_cloud_
         ))
      {
        if (crop_outside_)      
          indices.push_back ((*indices_)[index]);
        break;
      }
    }
    if (poly == hull_polygons_.size () && !crop_outside_)
      indices.push_back ((*indices_)[index]);
  }
}

template<typename PointT> void 
pcl::CropHull<PointT>::applyFilter3D (PointCloud &output)
{
  // This algorithm could definitely be sped up using kdtree/octree
  // information, if that is available!

  for (size_t index = 0; index < indices_->size (); index++)
  {
    // test ray-crossings for three random rays, and take vote of crossings
    // counts to determine if each point is inside the hull: the vote avoids
    // tricky edge and corner cases when rays might fluke through the edge
    // between two polygons
    // 'random' rays are arbitrary - basically anything that is less likely to
    // hit the edge between polygons than coordinate-axis aligned rays would
    // be.
    size_t crossings[3] = {0,0,0};
    Eigen::Vector3f rays[3] = 
    {
      Eigen::Vector3f (0.264882f,  0.688399f, 0.675237f),
      Eigen::Vector3f (0.0145419f, 0.732901f, 0.68018f),
      Eigen::Vector3f (0.856514f,  0.508771f, 0.0868081f)
    };

    for (size_t poly = 0; poly < hull_polygons_.size (); poly++)
      for (size_t ray = 0; ray < 3; ray++)
        crossings[ray] += rayTriangleIntersect
          (input_->points[(*indices_)[index]], rays[ray], hull_polygons_[poly], *hull_cloud_);

    if (crop_outside_ && (crossings[0]&1) + (crossings[1]&1) + (crossings[2]&1) > 1)
      output.push_back (input_->points[(*indices_)[index]]);
    else if (!crop_outside_)
      output.push_back (input_->points[(*indices_)[index]]);
  }
}

template<typename PointT> void 
pcl::CropHull<PointT>::applyFilter3D (std::vector<int> &indices)
{
  // see comments in applyFilter3D (PointCloud& output)
  for (size_t index = 0; index < indices_->size (); index++)
  {
    size_t crossings[3] = {0,0,0};
    Eigen::Vector3f rays[3] = 
    {
      Eigen::Vector3f(0.264882f,  0.688399f, 0.675237f),
      Eigen::Vector3f(0.0145419f, 0.732901f, 0.68018f),
      Eigen::Vector3f(0.856514f,  0.508771f, 0.0868081f)
    };

    for (size_t poly = 0; poly < hull_polygons_.size (); poly++)
      for (size_t ray = 0; ray < 3; ray++)
        crossings[ray] += rayTriangleIntersect
          (input_->points[(*indices_)[index]], rays[ray], hull_polygons_[poly], *hull_cloud_);

    if (crop_outside_ && (crossings[0]&1) + (crossings[1]&1) + (crossings[2]&1) > 1)
      indices.push_back ((*indices_)[index]);
    else if (!crop_outside_)
      indices.push_back ((*indices_)[index]);
  }
}

template<typename PointT> template<unsigned PlaneDim1, unsigned PlaneDim2> bool
pcl::CropHull<PointT>::isPointIn2DPolyWithVertIndices (
  const PointT& point, const Vertices& verts, const PointCloud& cloud)
{
  bool in_poly = false;
  double x1, x2, y1, y2;

  const int nr_poly_points = static_cast<const int>(verts.vertices.size ());
  double xold = cloud[verts.vertices[nr_poly_points - 1]].getVector3fMap ()[PlaneDim1];
  double yold = cloud[verts.vertices[nr_poly_points - 1]].getVector3fMap ()[PlaneDim2];
  for (int i = 0; i < nr_poly_points; i++)
  {
    const double xnew = cloud[verts.vertices[i]].getVector3fMap ()[PlaneDim1];
    const double ynew = cloud[verts.vertices[i]].getVector3fMap ()[PlaneDim2];
    if (xnew > xold)
    {
      x1 = xold;
      x2 = xnew;
      y1 = yold;
      y2 = ynew;
    }
    else
    {
      x1 = xnew;
      x2 = xold;
      y1 = ynew;
      y2 = yold;
    }

    if ((xnew < point.getVector3fMap ()[PlaneDim1]) == (point.getVector3fMap ()[PlaneDim1] <= xold) &&
        (point.getVector3fMap ()[PlaneDim2] - y1) * (x2 - x1) < (y2 - y1) * (point.getVector3fMap ()[PlaneDim1] - x1))
    {
      in_poly = !in_poly;
    }
    xold = xnew;
    yold = ynew;
  }

  return (in_poly);
}

template<typename PointT> bool
pcl::CropHull<PointT>::rayTriangleIntersect (const PointT& point,
                                             const Eigen::Vector3f& ray,
                                             const Vertices& verts,
                                             const PointCloud& cloud)
{
  // Algorithm here is adapted from:
  // http://softsurfer.com/Archive/algorithm_0105/algorithm_0105.htm#intersect_RayTriangle()
  //
  // Original copyright notice:
  // Copyright 2001, softSurfer (www.softsurfer.com)
  // This code may be freely used and modified for any purpose
  // providing that this copyright notice is included with it.
  //
  assert (verts.vertices.size () == 3);

  const Eigen::Vector3f p = point.getVector3fMap ();
  const Eigen::Vector3f a = cloud[verts.vertices[0]].getVector3fMap ();
  const Eigen::Vector3f b = cloud[verts.vertices[1]].getVector3fMap ();
  const Eigen::Vector3f c = cloud[verts.vertices[2]].getVector3fMap ();
  const Eigen::Vector3f u = b - a;
  const Eigen::Vector3f v = c - a;
  const Eigen::Vector3f n = u.cross (v);
  const float n_dot_ray = n.dot (ray);

  if (std::fabs (n_dot_ray) < 1e-9)
    return (false);

  const float r = n.dot (a - p) / n_dot_ray;

  if (r < 0)
    return (false);

  const Eigen::Vector3f w = p + r * ray - a;
  const float denominator = u.dot (v) * u.dot (v) - u.dot (u) * v.dot (v);
  const float s_numerator = u.dot (v) * w.dot (v) - v.dot (v) * w.dot (u);
  const float s = s_numerator / denominator;
  if (s < 0 || s > 1)
    return (false);

  const float t_numerator = u.dot (v) * w.dot (u) - u.dot (u) * w.dot (v);
  const float t = t_numerator / denominator;
  if (t < 0 || s+t > 1)
    return (false);
  
  return (true);
}

#define PCL_INSTANTIATE_CropHull(T) template class PCL_EXPORTS pcl::CropHull<T>;

#endif // PCL_FILTERS_IMPL_CROP_HULL_H_