frc971/vision/target_map.fbs

namespace frc971.vision;

table Position {
  x:double (id: 0);
  y:double (id: 1);
  z:double (id: 2);
}

table Quaternion {
  w:double (id: 0);
  x:double (id: 1);
  y:double (id: 2);
  z:double (id: 3);
}

// Represents 3d pose of an april tag on the field.
table TargetPoseFbs {
  // AprilTag ID of this target
  id:uint64 (id: 0);

  // Pose of target relative to either the field origin or camera.
  // To get the pose of the target, do:
  // Translation3d(position.x(), position.y(), position.z()) *
  // Quaterniond(orientation.w(), orientation.x(), orientation.y(), orientation.z())
  position:Position (id: 1);
  orientation:Quaternion (id: 2);

  // Minimum decision margin (confidence) for this april tag detection.
  // Only filled out if this pose represents a live detection.
  // NOTE: Detections with a decision margin less than
  // FLAGS_min_decision_margin in aprilrobotics.cc are already filtered
  // out before sending.
  confidence:double (id: 3);

  // Object-space error of the tag from pose estimation.
  // Only filled out if this pose represents a live detection.
  // Tags which are seen completely usually have a pose_error < 1e-6,
  // and a higher error could imply that part of the tag is being blocked.
  // NOTE: not filtered by aprilrobotics.cc so that we can log
  // more detections.
  pose_error:double (id: 4);

  // A measure of how much distortion affected this detection.
  // Only filled out if this pose represents a live detection.
  // This is computed as the average distance between the distorted
  // corners and undistorted corners, normalized by the image size
  // and the maximum expected distortion to be between 0-1.
  // NOTE: not filtered by aprilrobotics.cc so that we can log
  // more detections.
  distortion_factor:double (id: 5);

  // Ratio of pose_error from the best estimation to
  // pose error of the second best estimation.
  // Only filled out if this pose represents a live detection.
  // This should be significantly less than 1,
  // otherwise this pose may be a wrong solution.
  // NOTE: not filtered by aprilrobotics.cc so that we can log
  // more detections.
  pose_error_ratio:double (id: 6);
}

// Map of all target poses on a field.
// There are two possible uses for this:
// 1. Static april tag poses on the field solved for by TargetMapper.
// 2. List of detected april poses relative to the camera.
table TargetMap {
  target_poses:[TargetPoseFbs] (id: 0);

  // Unique name of the field (for use case 1.)
  field_name:string (id: 1);

  // End-of-frame timestamp for the frame with tag detections.
  // (for use case 2.).
  monotonic_timestamp_ns:int64 (id: 2);

  // Number of april tags rejected (cumulative) because
  // of low decision margin (affected by lighting).
  // We do the decision margin rejection in aprilrobotics
  // so we don't have an excessive amount of random target
  // detections (for use case 2).
  rejections:uint64 (id: 3);
}

root_type TargetMap;