Acts/Seeding/CompositeSpacePointLineSeeder.ipp

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/Seeding/CompositeSpacePointLineSeeder.hpp"
0012
0013 namespace Acts::Experimental {
0014
0015 constexpr CompositeSpacePointLineSeeder::TangentAmbi
0016 CompositeSpacePointLineSeeder::encodeAmbiguity(const int signTop,
0017                                                const int signBottom) {
0018   assert(Acts::abs(signTop) == 1 && Acts::abs(signBottom) == 1);
0019   using enum TangentAmbi;
0020   if (signTop == 1 && signBottom == 1) {
0021     return RR;
0022   } else if (signTop == 1 && signBottom == -1) {
0023     return RL;
0024   } else if (signTop == -1 && signBottom == 1) {
0025     return LR;
0026   }
0027   return LL;
0028 }
0029
0030 inline std::string CompositeSpacePointLineSeeder::toString(
0031     const TangentAmbi ambi) {
0032   switch (ambi) {
0033     using enum TangentAmbi;
0034     case RR:
0035       return "Right - Right";
0036     case RL:
0037       return "Right - Left";
0038     case LR:
0039       return "Left - Right";
0040     case LL:
0041       return "Left - Left";
0042   }
0043   return "Undefined";
0044 }
0045
0046 template <CompositeSpacePoint SpacePoint_t>
0047 CompositeSpacePointLineSeeder::TwoCircleTangentPars
0048 CompositeSpacePointLineSeeder::constructTangentLine(
0049     const SpacePoint_t& topHit, const SpacePoint_t& bottomHit,
0050     const TangentAmbi ambi) {
0051   using ResidualIdx = detail::CompSpacePointAuxiliaries::ResidualIdx;
0052   TwoCircleTangentPars result{};
0053   const auto& [signTop, signBot] = s_signCombo[toUnderlying(ambi)];
0054
0055   const Vector& bottomPos{bottomHit.localPosition()};
0056   const Vector& topPos{topHit.localPosition()};
0057   const Vector& eY{bottomHit.toNextSensor()};
0058   const Vector& eZ{bottomHit.planeNormal()};
0059
0060   const Vector D = topPos - bottomPos;
0061
0062   assert(Acts::abs(eY.dot(eZ)) < std::numeric_limits<double>::epsilon());
0063   assert(Acts::abs(bottomHit.sensorDirection().dot(eY)) <
0064          std::numeric_limits<double>::epsilon());
0065   assert(Acts::abs(bottomHit.sensorDirection().dot(eZ)) <
0066          std::numeric_limits<double>::epsilon());
0067
0068   assert(topHit.isStraw() && bottomHit.isStraw());
0069   const double dY = D.dot(eY);
0070   const double dZ = D.dot(eZ);
0071
0072   const double thetaTubes = std::atan2(dY, dZ);
0073   const double distTubes = Acts::fastHypot(dY, dZ);
0074
0075   constexpr auto covIdx = Acts::toUnderlying(ResidualIdx::bending);
0076   const double combDriftUncert{topHit.covariance()[covIdx] +
0077                                bottomHit.covariance()[covIdx]};
0078   const double R =
0079       -signBot * bottomHit.driftRadius() + signTop * topHit.driftRadius();
0080   result.theta = thetaTubes - std::asin(std::clamp(R / distTubes, -1., 1.));
0081   const double cosTheta = std::cos(result.theta);
0082   const double sinTheta = std::sin(result.theta);
0083   result.y0 = bottomPos.dot(eY) * cosTheta - bottomPos.dot(eZ) * sinTheta -
0084               signBot * bottomHit.driftRadius();
0085   assert(Acts::abs(topPos.dot(eY) * cosTheta - topPos.dot(eZ) * sinTheta -
0086                    signTop * topHit.driftRadius() - result.y0) <
0087          std::numeric_limits<float>::epsilon());
0088   result.y0 /= cosTheta;
0089   const double denomSquare = 1. - Acts::pow(R / distTubes, 2);
0090   if (denomSquare < std::numeric_limits<double>::epsilon()) {
0091     return result;
0092   }
0093   result.dTheta = combDriftUncert / std::sqrt(denomSquare) / distTubes;
0094   result.dY0 =
0095       std::hypot(bottomPos.dot(eY) * sinTheta + bottomPos.dot(eZ) * cosTheta,
0096                  1.) *
0097       result.dTheta;
0098   return result;
0099 }
0100 }  // namespace Acts::Experimental