// Copyright (c) 2018, ETH Zurich and UNC Chapel Hill.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//
//     * Redistributions in binary form must reproduce the above copyright
//       notice, this list of conditions and the following disclaimer in the
//       documentation and/or other materials provided with the distribution.
//
//     * Neither the name of ETH Zurich and UNC Chapel Hill nor the names of
//       its contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// Author: Johannes L. Schoenberger (jsch-at-demuc-dot-de)

#ifndef COLMAP_SRC_ESTIMATORS_GENERALIZED_ABSOLUTE_POSE_H_
#define COLMAP_SRC_ESTIMATORS_GENERALIZED_ABSOLUTE_POSE_H_

#include <Eigen/Core>
#include <vector>

#include "util/alignment.h"
#include "util/types.h"

namespace colmap {

// Solver for the Generalized P3P problem (NP3P or GP3P), based on:
//
//      Lee, Gim Hee, et al. "Minimal solutions for pose estimation of a
//      multi-camera system." Robotics Research. Springer International
//      Publishing, 2016. 521-538.
//
// This class is based on an original implementation by Federico Camposeco.
class GP3PEstimator {
 public:
  // The generalized image observations, which is composed of the relative pose
  // of the specific camera in the generalized camera and its image observation.
  struct X_t {
    EIGEN_MAKE_ALIGNED_OPERATOR_NEW
    // The relative transformation from the generalized camera to the camera
    // frame of the observation.
    Eigen::Matrix3x4d rel_tform;
    // The 2D image feature observation.
    Eigen::Vector2d xy;
  };

  // The observed 3D feature points in the world frame.
  typedef Eigen::Vector3d Y_t;
  // The transformation from the world to the generalized camera frame.
  typedef Eigen::Matrix3x4d M_t;

  // The minimum number of samples needed to estimate a model.
  static const int kMinNumSamples = 3;

  // Estimate the most probable solution of the GP3P problem from a set of
  // three 2D-3D point correspondences.
  static std::vector<M_t> Estimate(const std::vector<X_t>& points2D,
                                   const std::vector<Y_t>& points3D);

  // Calculate the squared cosine distance error between the rays given a set of
  // 2D-3D point correspondences and a projection matrix of the generalized
  // camera.
  static void Residuals(const std::vector<X_t>& points2D,
                        const std::vector<Y_t>& points3D,
                        const M_t& proj_matrix, std::vector<double>* residuals);
};

}  // namespace colmap

EIGEN_DEFINE_STL_VECTOR_SPECIALIZATION_CUSTOM(colmap::GP3PEstimator::X_t)

#endif  // COLMAP_SRC_ESTIMATORS_GENERALIZED_ABSOLUTE_POSE_H_
