src/Utilities/EventDataTransforms.cpp

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 #include "ActsExamples/Utilities/EventDataTransforms.hpp"
0010
0011 #include "Acts/EventData/SourceLink.hpp"
0012 #include "ActsExamples/EventData/IndexSourceLink.hpp"
0013 #include "ActsExamples/EventData/SimSpacePoint.hpp"
0014
0015 #include <algorithm>
0016 #include <vector>
0017
0018 ActsExamples::ProtoTrack ActsExamples::seedToPrototrack(
0019     const ActsExamples::SimSeed& seed) {
0020   ProtoTrack track;
0021   track.reserve(seed.sp().size());
0022   for (const auto& spacePoints : seed.sp()) {
0023     for (const auto& slink : spacePoints->sourceLinks()) {
0024       const auto& islink = slink.get<IndexSourceLink>();
0025       track.emplace_back(islink.index());
0026     }
0027   }
0028   return track;
0029 }
0030
0031 const ActsExamples::SimSpacePoint* ActsExamples::findSpacePointForIndex(
0032     ActsExamples::Index index, const SimSpacePointContainer& spacepoints) {
0033   auto match = [&](const SimSpacePoint& sp) {
0034     const auto& sls = sp.sourceLinks();
0035     return std::ranges::any_of(sls, [&](const auto& sl) {
0036       return sl.template get<IndexSourceLink>().index() == index;
0037     });
0038   };
0039
0040   auto found = std::ranges::find_if(spacepoints, match);
0041
0042   if (found == spacepoints.end()) {
0043     return nullptr;
0044   }
0045
0046   return &(*found);
0047 }
0048
0049 ActsExamples::SimSeed ActsExamples::prototrackToSeed(
0050     const ActsExamples::ProtoTrack& track,
0051     const ActsExamples::SimSpacePointContainer& spacepoints) {
0052   auto findSpacePoint = [&](ActsExamples::Index index) {
0053     auto found = findSpacePointForIndex(index, spacepoints);
0054     if (found == nullptr) {
0055       throw std::runtime_error("No spacepoint found for source-link index " +
0056                                std::to_string(index));
0057     }
0058     return found;
0059   };
0060
0061   const auto s = track.size();
0062   if (s < 3) {
0063     throw std::runtime_error(
0064         "Cannot convert track with less then 3 spacepoints to seed");
0065   }
0066
0067   std::vector<const SimSpacePoint*> ps;
0068   ps.reserve(track.size());
0069
0070   std::transform(track.begin(), track.end(), std::back_inserter(ps),
0071                  findSpacePoint);
0072   std::ranges::sort(ps, {}, [](const auto& p) { return p->r(); });
0073
0074   // Simply use r = m*z + t and solve for r=0 to find z vertex position...
0075   // Probably not the textbook way to do
0076   const auto m =
0077       (ps.back()->r() - ps.front()->r()) / (ps.back()->z() - ps.front()->z());
0078   const auto t = ps.front()->r() - m * ps.front()->z();
0079   const auto z_vertex = -t / m;
0080
0081   SimSeed seed(*ps[0], *ps[s / 2], *ps[s - 1]);
0082   seed.setVertexZ(z_vertex);
0083   return seed;
0084 }