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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/EventData/TrackParameters.hpp"
0012 #include "Acts/Geometry/GeometryContext.hpp"
0013 #include "Acts/MagneticField/MagneticFieldContext.hpp"
0014 #include "Acts/Material/interface/IAssignmentFinder.hpp"
0015 #include "Acts/Propagator/ActorList.hpp"
0016 #include "Acts/Propagator/SurfaceCollector.hpp"
0017 #include "Acts/Surfaces/Surface.hpp"
0018 #include "Acts/Utilities/Logger.hpp"
0019 #include "Acts/Utilities/VectorHelpers.hpp"
0020 
0021 #include <map>
0022 #include <utility>
0023 #include <vector>
0024 
0025 namespace Acts {
0026 
0027 /// @brief selector for finding surface
0028 ///
0029 /// This is to be used with a SurfaceCollector<>
0030 struct MaterialSurfaceIdentifier {
0031   /// check if the surface has material
0032   /// @param sf Surface to check for material
0033   /// @return True if the surface has material assigned to it
0034   bool operator()(const Surface& sf) const {
0035     return (sf.surfaceMaterial() != nullptr);
0036   }
0037 };
0038 
0039 /// An Interaction volume collector with unique counting
0040 struct InteractionVolumeCollector {
0041   /// Simple result struct that holds the collected volumes
0042   ///
0043   /// @note the map is to avoid double counting as this is
0044   /// called in an action list
0045   struct this_result {
0046     /// Map of collected volume assignments by geometry identifier
0047     std::map<GeometryIdentifier, IAssignmentFinder::VolumeAssignment> collected;
0048   };
0049 
0050   /// Type alias for volume collection result
0051   using result_type = this_result;
0052 
0053   /// Collector action for the ActionList of the Propagator
0054   /// It checks if the propagator state has a current volume,
0055   /// in which case the action is performed:
0056   /// - it records the volume given the configuration
0057   ///
0058   /// @tparam propagator_state_t is the type of Propagator state
0059   /// @tparam stepper_t Type of the stepper used for the propagation
0060   /// @tparam navigator_t Type of the navigator used for the propagation
0061   ///
0062   /// @param [in,out] state is the mutable stepper state object
0063   /// @param [in] stepper The stepper in use
0064   /// @param [in] navigator The navigator in use
0065   /// @param [in,out] result is the mutable result object
0066   template <typename propagator_state_t, typename stepper_t,
0067             typename navigator_t>
0068   void act(propagator_state_t& state, const stepper_t& stepper,
0069            const navigator_t& navigator, result_type& result,
0070            const Logger& /*logger*/) const {
0071     // Retrieve the current volume
0072     auto currentVolume = navigator.currentVolume(state.navigation);
0073 
0074     // The current volume has been assigned by the navigator
0075     if (currentVolume != nullptr) {
0076       auto collIt = result.collected.find(currentVolume->geometryId());
0077       // Check if the volume has been collected and if it has material
0078       if (collIt == result.collected.end() &&
0079           currentVolume->volumeMaterial() != nullptr) {
0080         Vector3 entryPosition = stepper.position(state.stepping);
0081         Vector3 exitPosition = entryPosition;
0082         IAssignmentFinder::VolumeAssignment vAssignment{
0083             InteractionVolume(currentVolume), entryPosition, exitPosition};
0084         result.collected.emplace(currentVolume->geometryId(), vAssignment);
0085       } else if (collIt != result.collected.end()) {
0086         // Update the exit position
0087         (collIt->second).exit = stepper.position(state.stepping);
0088       }
0089     }
0090   }
0091 };
0092 
0093 /// @class PropagatorMaterialAssigner
0094 ///
0095 /// A Propagator based material assigner that uses the navigation and
0096 /// transport of the propagator to assign the material to the surface
0097 /// or the volume.
0098 ///
0099 /// @note eventual navigation problems would affect he material mapping
0100 template <typename propagator_t>
0101 class PropagatorMaterialAssigner final : public IAssignmentFinder {
0102  public:
0103   /// @brief  Construct with propagator
0104   /// @param propagator
0105   explicit PropagatorMaterialAssigner(propagator_t propagator)
0106       : m_propagator(std::move(propagator)) {}
0107 
0108   /// @brief Method for generating assignment candidates for the
0109   /// material interaction assignment to surfaces or volumes
0110   ///
0111   /// @param gctx is the geometry context
0112   /// @param mctx is the magnetic field context
0113   /// @param position is the position of the initial ray
0114   /// @param direction is the direction of initial ray
0115   ///
0116   /// @return a vector of Surface Assignments and Volume Assignments
0117   std::pair<std::vector<IAssignmentFinder::SurfaceAssignment>,
0118             std::vector<IAssignmentFinder::VolumeAssignment>>
0119   assignmentCandidates(const GeometryContext& gctx,
0120                        const MagneticFieldContext& mctx,
0121                        const Vector3& position,
0122                        const Vector3& direction) const final {
0123     // Return container
0124     std::pair<std::vector<IAssignmentFinder::SurfaceAssignment>,
0125               std::vector<IAssignmentFinder::VolumeAssignment>>
0126         candidates;
0127 
0128     using VectorHelpers::makeVector4;
0129     // Neutral curvilinear parameters
0130     NeutralBoundTrackParameters start =
0131         NeutralBoundTrackParameters::createCurvilinear(
0132             makeVector4(position, 0), direction, 1, std::nullopt,
0133             NeutralParticleHypothesis::geantino());
0134 
0135     // Prepare Action list and abort list
0136     using MaterialSurfaceCollector =
0137         SurfaceCollector<MaterialSurfaceIdentifier>;
0138     using ActorList = ActorList<MaterialSurfaceCollector,
0139                                 InteractionVolumeCollector, EndOfWorldReached>;
0140     using PropagatorOptions =
0141         typename propagator_t::template Options<ActorList>;
0142 
0143     PropagatorOptions options(gctx, mctx);
0144 
0145     const auto& result = m_propagator.propagate(start, options).value();
0146 
0147     // The surface collection results
0148     auto scResult =
0149         result.template get<MaterialSurfaceCollector::result_type>();
0150     auto mappingSurfaces = scResult.collected;
0151 
0152     for (auto& mSurface : mappingSurfaces) {
0153       candidates.first.push_back(IAssignmentFinder::SurfaceAssignment{
0154           mSurface.surface, mSurface.position, direction});
0155     }
0156 
0157     // The volume collection results
0158     auto vcResult =
0159         result.template get<InteractionVolumeCollector::result_type>();
0160     for (const auto& [geoId, vIntersection] : vcResult.collected) {
0161       candidates.second.push_back(vIntersection);
0162     }
0163 
0164     // Return the candidates
0165     return candidates;
0166   }
0167 
0168  private:
0169   propagator_t m_propagator;
0170 };
0171 
0172 }  // namespace Acts