// Copyright (c) 2013  INRIA Bordeaux Sud-Ouest (France), All rights reserved.
// Copyright (c) 2013 GeometryFactory
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v5.6.1/Surface_mesh_deformation/include/CGAL/Deformation_Eigen_closest_rotation_traits_3.h $
// $Id: Deformation_Eigen_closest_rotation_traits_3.h a98b548 2022-05-12T16:03:53+02:00 Sven Oesau
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
// Author(s)     : Gael Guennebaud and Ilker O. Yaz


#ifndef CGAL_DEFORMATION_EIGEN_CLOSEST_ROTATION_TRAITS_3_H
#define CGAL_DEFORMATION_EIGEN_CLOSEST_ROTATION_TRAITS_3_H

#include <Eigen/Eigen>
#include <Eigen/SVD>

namespace CGAL {
/// \ingroup PkgSurfaceMeshDeformationRef
/// A class to compute the closest rotation in Frobenius norm to a 3x3 Matrix using the \link thirdpartyEigen `Eigen` library \endlink.
/// The internal computation relies on `Eigen::JacobiSVD<>` solver.
///
/// \cgalModels `DeformationClosestRotationTraits_3`
class Deformation_Eigen_closest_rotation_traits_3{
public:

  /// \cond SKIP_FROM_MANUAL
  typedef Eigen::Matrix3d Matrix;
  typedef Eigen::Vector3d Vector;

  /// Equivalent to `result += w * (v1*v2^t)`
  void add_scalar_t_vector_t_vector_transpose(Matrix& result, double w, const Vector& v1, const Vector& v2)
  {
    result += w * (v1*v2.transpose());
  }

  /// Equivalent to `result += (w1*m1 + w2*m2) * v`
  void add__scalar_t_matrix_p_scalar_t_matrix__t_vector(Vector& result, double w1, const Matrix& m1, double w2, const Matrix& m2, const Vector& v)
  {
    result += (w1*m1 + w2*m2) * v;
  }

  /// Equivalent to `result += w * (m1 + m2 + m3) * v`
  void add_scalar_t_matrix_sum_t_vector(Vector& result, double w, const Matrix& m1, const Matrix& m2, const Matrix& m3, const Vector& v)
  {
    result += w * (m1 + m2 + m3) * v;
  }

  /// Returns the squared norm of `v1 - m*v2`
  double squared_norm_vector_scalar_vector_subs(const Vector& v1, const Matrix& m, const Vector& v2)
  {
    return (v1 - m*v2).squaredNorm();
  }

  /// Returns an identity matrix
  Matrix identity_matrix()
  {
    return Matrix().setIdentity();
  }

  /// Returns a zero initialized matrix
  Matrix zero_matrix()
  {
    return Matrix().setZero();
  }

  /// Returns vector initialized with parameters
  Vector vector(double x, double y, double z)
  {
    return Vector(x, y, z);
  }

  /// Returns a coefficient of a vector
  double vector_coordinate(const Vector& v, int i)
  {
    return v(i);
  }

  /// Computes the closest rotation to `m` and places it into `R`
  void compute_close_rotation(const Matrix& m, Matrix& R)
  {
#if EIGEN_VERSION_AT_LEAST(3,4,90)
    Eigen::JacobiSVD<Eigen::Matrix3d, Eigen::ComputeFullU | Eigen::ComputeFullV> solver;
    solver.compute(m);
#else
    Eigen::JacobiSVD<Eigen::Matrix3d> solver;
    solver.compute(m, Eigen::ComputeFullU | Eigen::ComputeFullV);
#endif

    const Matrix& u = solver.matrixU(); const Matrix& v = solver.matrixV();
    R = v * u.transpose();

    if( R.determinant() < 0 ) {
      Matrix u_copy = u;
      u_copy.col(2) *= -1;        // singular values sorted ascendingly
      R = v * u_copy.transpose(); // re-extract rotation matrix
    }
  }

  /// \endcond

};

}//namespace CGAL
#endif // CGAL_DEFORMATION_EIGEN_CLOSEST_ROTATION_TRAITS_3_H

