obstacles.cpp

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#include <teb_local_planner/obstacles.h>
#include <ros/console.h>
// #include <teb_local_planner/misc.h>

namespace teb_local_planner
{


void PolygonObstacle::fixPolygonClosure()
{
  if (vertices_.size()<2)
    return;
  
  if (vertices_.front().isApprox(vertices_.back()))
    vertices_.pop_back();
}

void PolygonObstacle::calcCentroid()
{
  if (vertices_.empty())
  {
    centroid_.setConstant(NAN);
    ROS_WARN("PolygonObstacle::calcCentroid(): number of vertices is empty. the resulting centroid is a vector of NANs.");
    return;
  }
  
  // if polygon is a point
  if (noVertices()==1)
  {
    centroid_ = vertices_.front();
    return;
  }
  
  // if polygon is a line:
  if (noVertices()==2)
  {
    centroid_ = 0.5*(vertices_.front() + vertices_.back());
    return;
  }
  
  // otherwise:
  
  centroid_.setZero();
    
  // calculate centroid (see wikipedia http://de.wikipedia.org/wiki/Geometrischer_Schwerpunkt#Polygon)
  double A = 0;  // A = 0.5 * sum_0_n-1 (x_i * y_{i+1} - x_{i+1} * y_i)
  for (int i=0; i<(int)noVertices()-1; ++i)
  {
    A += vertices_.at(i).coeffRef(0) * vertices_.at(i+1).coeffRef(1) - vertices_.at(i+1).coeffRef(0) * vertices_.at(i).coeffRef(1);
  }
  A += vertices_.at(noVertices()-1).coeffRef(0) * vertices_.at(0).coeffRef(1) - vertices_.at(0).coeffRef(0) * vertices_.at(noVertices()-1).coeffRef(1);
  A *= 0.5;
  
  if (A!=0)
  {
    for (int i=0; i<(int)noVertices()-1; ++i)
    {
      double aux = (vertices_.at(i).coeffRef(0) * vertices_.at(i+1).coeffRef(1) - vertices_.at(i+1).coeffRef(0) * vertices_.at(i).coeffRef(1));
      centroid_ +=  ( vertices_.at(i) + vertices_.at(i+1) )*aux;
    }
    double aux = (vertices_.at(noVertices()-1).coeffRef(0) * vertices_.at(0).coeffRef(1) - vertices_.at(0).coeffRef(0) * vertices_.at(noVertices()-1).coeffRef(1));
    centroid_ +=  ( vertices_.at(noVertices()-1) + vertices_.at(0) )*aux;
    centroid_ /= (6*A); 
  }
  else // A == 0 -> all points are placed on a 'perfect' line
  {
    // seach for the two outer points of the line with the maximum distance inbetween
    int i_cand = 0;
    int j_cand = 0;
    double min_dist = HUGE_VAL;
    for (int i=0; i<(int)noVertices(); ++i)
    {
      for (int j=i+1; j<(int)noVertices(); ++j) // start with j=i+1
      {
        double dist = (vertices_[j] - vertices_[i]).norm();
        if (dist < min_dist)
        {
          min_dist = dist;
          i_cand = i;
          j_cand = j;
        }
      }
    }
    // calc centroid of that line
    centroid_ = 0.5*(vertices_[i_cand] + vertices_[j_cand]);
  }
}



Eigen::Vector2d PolygonObstacle::getClosestPoint(const Eigen::Vector2d& position) const
{
 // the polygon is a point
  if (noVertices() == 1)
  {
    return vertices_.front();
  }
  
  if (noVertices() > 1)
  {
    
    Eigen::Vector2d new_pt = closest_point_on_line_segment_2d(position, vertices_.at(0), vertices_.at(1));
    
    if (noVertices() > 2) // real polygon and not a line
    {
      double dist = (new_pt-position).norm();
      Eigen::Vector2d closest_pt = new_pt;
      
      // check each polygon edge
      for (int i=1; i<(int)noVertices()-1; ++i) // skip the first one, since we already checked it (new_pt)
      {
        new_pt = closest_point_on_line_segment_2d(position, vertices_.at(i), vertices_.at(i+1));
        double new_dist = (new_pt-position).norm();
        if (new_dist < dist)
        {
          dist = new_dist;
          closest_pt = new_pt;
        }
      }
      // afterwards we check the edge between goal and start (close polygon)
      new_pt = closest_point_on_line_segment_2d(position, vertices_.back(), vertices_.front());
      double new_dist = (new_pt-position).norm();
      if (new_dist < dist)
        return new_pt;
      else
        return closest_pt;
    }
    else
    {
      return new_pt; // closest point on line segment
    }
  }
  
  ROS_ERROR("PolygonObstacle::getClosestPoint() cannot find any closest point. Polygon ill-defined?");
  return Eigen::Vector2d::Zero(); // todo: maybe boost::optional?
}


bool PolygonObstacle::checkLineIntersection(const Eigen::Vector2d& line_start, const Eigen::Vector2d& line_end, double min_dist) const
{
  // Simple strategy, check all edge-line intersections until an intersection is found...
  // check each polygon edge
  for (unsigned int i=0; i<vertices_.size()-1; ++i)
  {
    if ( check_line_segments_intersection_2d(line_start, line_end, vertices_.at(i), vertices_.at(i+1)) ) 
      return true;
  }
  if (noVertices()==2) // if polygon is a line
    return false;
  
  return check_line_segments_intersection_2d(line_start, line_end, vertices_.back(), vertices_.front()); //otherwise close polygon
}



// implements toPolygonMsg() of the base class
void PolygonObstacle::toPolygonMsg(geometry_msgs::Polygon& polygon)
{
  polygon.points.resize(vertices_.size());
  for (std::size_t i=0; i<vertices_.size(); ++i)
  {
    polygon.points[i].x = vertices_[i].x();
    polygon.points[i].y = vertices_[i].y();
    polygon.points[i].z = 0;
  }
}








} // namespace teb_local_planner