Utilities/detail/Line3DWithPartialDerivatives.hpp

0001 // This file is part of the ACTS project.
0002 //
0003 // Copyright (C) 2016 CERN for the benefit of the ACTS project
0004 //
0005 // This Source Code Form is subject to the terms of the Mozilla Public
0006 // License, v. 2.0. If a copy of the MPL was not distributed with this
0007 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
0008
0009 #pragma once
0010
0011 #include "Acts/Definitions/Algebra.hpp"
0012 #include "Acts/Utilities/AlgebraHelpers.hpp"
0013 #include "Acts/Utilities/ArrayHelpers.hpp"
0014
0015 #include <cstdint>
0016
0017 namespace Acts::detail {
0018 /// @brief Helper to describe a line in 3D space. The line is described
0019 ///        by a point on the line and a corresponding direction vector with unit
0020 ///        length. Additionally, the `Line3DWithPartialDerivatives` holds the
0021 ///        first and second derivative of the line with respect to the
0022 ///        parameters `x0`, `y0`, `theta`, and `phi` (the parameters are defined
0023 ///        in the enum `ParIndex`).
0024 template <std::floating_point T>
0025 class Line3DWithPartialDerivatives {
0026  public:
0027   /// @brief Abrivation of the Vector
0028   using Vector = Eigen::Matrix<T, 3, 1>;
0029   /// @brief Enum to map the indices of the parameter vector
0030   enum class ParIndex : std::uint8_t {
0031     y0 = 0,     /// y-axis intercept at z=0
0032     theta = 1,  /// polar angle w.r.t the z-axis
0033     x0 = 2,     /// x-axis intercept at z=0
0034     phi = 3,    /// Azimuthal angle in the x-y plane
0035     nPars = 4,  /// Number of line parameters
0036   };
0037   static constexpr auto s_nPars = static_cast<std::size_t>(ParIndex::nPars);
0038   /// @brief Abrivation of the parameter vector type
0039   using ParamVector = std::array<T, s_nPars>;
0040   /// @brief default constructor
0041   Line3DWithPartialDerivatives() = default;
0042   /// @brief Default copy constructor
0043   Line3DWithPartialDerivatives(
0044       const Line3DWithPartialDerivatives& other) noexcept = default;
0045   /// @brief Default move constructor
0046   Line3DWithPartialDerivatives(Line3DWithPartialDerivatives&& other) noexcept =
0047       default;
0048   /// @brief Default assignment operator
0049   Line3DWithPartialDerivatives& operator=(
0050       const Line3DWithPartialDerivatives& other) noexcept = default;
0051   /// @brief Default move assignemt operator
0052   Line3DWithPartialDerivatives& operator=(
0053       Line3DWithPartialDerivatives&& other) noexcept = default;
0054   /// @brief Constructor taking a parameter array which is at least as big as the ParamVector
0055   ///        The first 4 indices are interpreted as the corresponding line
0056   ///        parameters
0057   template <std::size_t N>
0058   explicit Line3DWithPartialDerivatives(
0059       const std::array<T, N>& initPars) noexcept;
0060
0061   /// @brief Update the line & derivatives with the new parameters
0062   /// @param newPars The new parameters to update the line with
0063   template <std::size_t N>
0064   void updateParameters(const std::array<T, N>& newPars) noexcept
0065     requires(N >= s_nPars);
0066   /// @brief Returns a point on the line
0067   const Vector& position() const;
0068   /// @brief Returns the direction of the line
0069   const Vector& direction() const;
0070   /// @brief Returns the first derivative of the line with respect to the passed
0071   /// @param param: Index of the parameter to get the derivative for
0072   const Vector& gradient(const ParIndex param) const;
0073   /// @brief Returns the second derivative of the line with respect to the passed
0074   /// @param param1: Index of the first parameter to get the derivative for
0075   /// @param param2: Index of the second parameter to get the derivative for
0076   const Vector& hessian(const ParIndex param1, const ParIndex param2) const;
0077   /// @brief Returns a point along the line which is by lambda apart from
0078   ///        the line reference
0079   /// @param lambda: Separation from the reference
0080   Vector point(const double lambda) const;
0081   /// @brief Returns the currently set parameters
0082   ParamVector parameters() const;
0083
0084  private:
0085   Vector m_pos{Vector::Zero()};
0086   Vector m_dir{Vector::UnitZ()};
0087   std::array<Vector, s_nPars> m_gradient{
0088       filledArray<Vector, s_nPars>(Vector::Zero())};
0089
0090   std::array<Vector, sumUpToN(s_nPars)> m_hessian{
0091       filledArray<Vector, sumUpToN(s_nPars)>(Vector::Zero())};
0092 };
0093 }  // namespace Acts::detail
0094 #include "Acts/Utilities/detail/Line3DWithPartialDerivatives.ipp"