ScalableBField.hpp

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// This file is part of the Acts project.
//
// Copyright (C) 2016-2018 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 "Acts/MagneticField/MagneticFieldContext.hpp"
#include "Acts/Utilities/Definitions.hpp"

namespace ActsExamples {

namespace BField {

struct ScalableBFieldContext {
  double scalor = 1.;
};

class ScalableBField final {
 public:
  struct Cache {
    double scalor = 1.;

    Cache(const Acts::MagneticFieldContext& mcfg) {
      scalor = std::any_cast<const ScalableBFieldContext>(mcfg).scalor;
    }
  };

  explicit ScalableBField(Acts::Vector3D B) : m_BField(std::move(B)) {}

  ScalableBField(double Bx = 0., double By = 0., double Bz = 0.)
      : m_BField(Bx, By, Bz) {}

  Acts::Vector3D getField(const Acts::Vector3D& /*position*/) const {
    return m_BField;
  }

  Acts::Vector3D getField(const Acts::Vector3D& /*position*/,
                          Cache& cache) const {
    return m_BField * cache.scalor;
  }

  Acts::Vector3D getFieldGradient(
      const Acts::Vector3D& /*position*/,
      Acts::ActsMatrixD<3, 3>& /*derivative*/) const {
    return m_BField;
  }

  Acts::Vector3D getFieldGradient(const Acts::Vector3D& /*position*/,
                                  Acts::ActsMatrixD<3, 3>& /*derivative*/,
                                  Cache& cache) const {
    return m_BField * cache.scalor;
  }

  bool isInside(const Acts::Vector3D& /*position*/) const { return true; }

  void setField(double Bx, double By, double Bz) { m_BField << Bx, By, Bz; }

  void setField(const Acts::Vector3D& B) { m_BField = B; }

 private:
  Acts::Vector3D m_BField;
};

}  // namespace BField
}  // namespace ActsExamples