trajectory_utils.cpp

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#include <dwb_local_planner/trajectory_utils.h>
#include <nav_core2/exceptions.h>

namespace dwb_local_planner
{
const geometry_msgs::Pose2D& getClosestPose(const dwb_msgs::Trajectory2D& trajectory, const double time_offset)
{
  ros::Duration goal_time(time_offset);
  const unsigned int num_poses = trajectory.poses.size();
  if (num_poses == 0)
  {
    throw nav_core2::PlannerException("Cannot call getClosestPose on empty trajectory.");
  }
  unsigned int closest_index = num_poses;
  double closest_diff = 0.0;
  for (unsigned int i=0; i < num_poses; ++i)
  {
    double diff = fabs((trajectory.time_offsets[i] - goal_time).toSec());
    if (closest_index == num_poses || diff < closest_diff)
    {
      closest_index = i;
      closest_diff = diff;
    }
    if (goal_time < trajectory.time_offsets[i])
    {
      break;
    }
  }
  return trajectory.poses[closest_index];
}

geometry_msgs::Pose2D projectPose(const dwb_msgs::Trajectory2D& trajectory, const double time_offset)
{
  ros::Duration goal_time(time_offset);
  const unsigned int num_poses = trajectory.poses.size();
  if (num_poses == 0)
  {
    throw nav_core2::PlannerException("Cannot call projectPose on empty trajectory.");
  }
  if (goal_time <= trajectory.time_offsets[0])
  {
    return trajectory.poses[0];
  }
  else if (goal_time >= trajectory.time_offsets[num_poses - 1])
  {
    return trajectory.poses[num_poses - 1];
  }

  for (unsigned int i=0; i < num_poses - 1; ++i)
  {
    if (goal_time >= trajectory.time_offsets[i] && goal_time < trajectory.time_offsets[i+1])
    {
      double time_diff = (trajectory.time_offsets[i+1] - trajectory.time_offsets[i]).toSec();
      double ratio = (goal_time - trajectory.time_offsets[i]).toSec() / time_diff;
      double inv_ratio = 1.0 - ratio;
      const geometry_msgs::Pose2D& pose_a = trajectory.poses[i];
      const geometry_msgs::Pose2D& pose_b = trajectory.poses[i + 1];
      geometry_msgs::Pose2D projected;
      projected.x     = pose_a.x     * inv_ratio + pose_b.x     * ratio;
      projected.y     = pose_a.y     * inv_ratio + pose_b.y     * ratio;
      projected.theta = pose_a.theta * inv_ratio + pose_b.theta * ratio;
      return projected;
    }
  }

  // Should not reach this point
  return trajectory.poses[num_poses - 1];
}


}  // namespace dwb_local_planner