von_neumann_path.cpp

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#include <dlux_plugins/von_neumann_path.h>
#include <nav_grid/coordinate_conversion.h>
#include <nav_core2/exceptions.h>
#include <limits>
#include <pluginlib/class_list_macros.h>
 
PLUGINLIB_EXPORT_CLASS(dlux_plugins::VonNeumannPath, dlux_global_planner::Traceback)
 
namespace dlux_plugins
{
nav_2d_msgs::Path2D VonNeumannPath::getPath(const dlux_global_planner::PotentialGrid& potential_grid,
                                            const geometry_msgs::Pose2D& start, const geometry_msgs::Pose2D& goal,
                                            double& path_cost)
{
  nav_2d_msgs::Path2D path;
  path_cost = 0.0;
 
  unsigned int current_x = 0, current_y = 0;
  worldToGridBounded(potential_grid.getInfo(), start.x, start.y, current_x, current_y);
 
  // Add 0.5 to represent center of the cell
  geometry_msgs::Pose2D current;
  current.x = current_x + 0.5;
  current.y = current_y + 0.5;
  path.poses.push_back(current);
  path_cost += cost_interpreter_->getCost(current_x, current_y);
 
  unsigned int goal_index = potential_grid.getIndex(goal.x, goal.y);
 
  // Main Loop
  while (potential_grid.getIndex(current_x, current_y) != goal_index)
  {
    float min_val = std::numeric_limits<float>::max();
    unsigned int min_x = 0, min_y = 0;
    unsigned int x, y;
    int index;
 
    // Check the four neighbors
    if (current_x > 0)
    {
      x = current_x - 1;
      y = current_y;
      index = potential_grid.getIndex(x, y);
      if (potential_grid[index] < min_val)
      {
        min_val = potential_grid[index];
        min_x = x;
        min_y = y;
      }
    }
    if (current_x < potential_grid.getWidth() - 1)
    {
      x = current_x + 1;
      y = current_y;
      index = potential_grid.getIndex(x, y);
      if (potential_grid[index] < min_val)
      {
        min_val = potential_grid[index];
        min_x = x;
        min_y = y;
      }
    }
    if (current_y > 0)
    {
      x = current_x;
      y = current_y - 1;
      index = potential_grid.getIndex(x, y);
      if (potential_grid[index] < min_val)
      {
        min_val = potential_grid[index];
        min_x = x;
        min_y = y;
      }
    }
    if (current_y < potential_grid.getHeight() - 1)
    {
      x = current_x;
      y = current_y + 1;
      index = potential_grid.getIndex(x, y);
      if (potential_grid[index] < min_val)
      {
        min_val = potential_grid[index];
        min_x = x;
        min_y = y;
      }
    }
 
    if (min_val == std::numeric_limits<float>::max())
      throw nav_core2::PlannerException("Reached dead end in traceback.");
 
    // Move to the Min Neighbor
    current_x = min_x;
    current_y = min_y;
 
    // Add 0.5 to represent center of the cell
    current.x = current_x + 0.5;
    current.y = current_y + 0.5;
    path.poses.push_back(current);
    path_cost += cost_interpreter_->getCost(current_x, current_y);
  }
  return mapPathToWorldPath(path, potential_grid.getInfo());
}
 
}  // namespace dlux_plugins