coordinate_transformations.hpp

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// This file is part of the Acts project.
//
// Copyright (C) 2016-2019 CERN for the benefit of the Acts project
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

#pragma once

#include <cmath>
#include "Acts/Geometry/GeometryContext.hpp"
#include "Acts/Surfaces/Surface.hpp"
#include "Acts/Utilities/ParameterDefinitions.hpp"

#ifdef ACTS_COORDINATE_TRANSFORM_PLUGIN

#include ACTS_COORDINATE_TRANSFORM_PLUGIN

#else

namespace Acts {
namespace detail {

struct coordinate_transformation {
  using ParVector_t = BoundVector;

  static ActsVectorD<3> parameters2globalPosition(const GeometryContext& gctx,
                                                  const ParVector_t& pars,
                                                  const Surface& s) {
    ActsVectorD<3> globalPosition;
    s.localToGlobal(gctx,
                    ActsVectorD<2>(pars(Acts::eLOC_0), pars(Acts::eLOC_1)),
                    parameters2globalMomentum(pars), globalPosition);
    return globalPosition;
  }

  static ActsVectorD<3> parameters2globalMomentum(const ParVector_t& pars) {
    ActsVectorD<3> momentum;
    double p = std::abs(1. / pars(Acts::eQOP));
    double phi = pars(Acts::ePHI);
    double theta = pars(Acts::eTHETA);
    momentum << p * sin(theta) * cos(phi), p * sin(theta) * sin(phi),
        p * cos(theta);

    return momentum;
  }

  static ParVector_t global2curvilinear(const ActsVectorD<3>& /*pos*/,
                                        const ActsVectorD<3>& mom,
                                        double charge, double time) {
    using VectorHelpers::phi;
    using VectorHelpers::theta;
    ParVector_t parameters;
    parameters << 0, 0, phi(mom), theta(mom),
        ((std::abs(charge) < 1e-4) ? 1. : charge) / mom.norm(), time;

    return parameters;
  }

  static ParVector_t global2parameters(const GeometryContext& gctx,
                                       const ActsVectorD<3>& pos,
                                       const ActsVectorD<3>& mom, double charge,
                                       double time, const Surface& s) {
    using VectorHelpers::phi;
    using VectorHelpers::theta;
    ActsVectorD<2> localPosition;
    s.globalToLocal(gctx, pos, mom, localPosition);
    ParVector_t result;
    result << localPosition(0), localPosition(1), phi(mom), theta(mom),
        ((std::abs(charge) < 1e-4) ? 1. : charge) / mom.norm(), time;
    return result;
  }

  static double parameters2charge(const ParVector_t& pars) {
    return (pars(Acts::eQOP) > 0) ? 1. : -1.;
  }
};
}  // namespace detail
}  // namespace Acts

#endif  // ACTS_COORDINATE_TRANSFORM_PLUGIN