src/EventData/TransformationHelpers.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 "Acts/EventData/TransformationHelpers.hpp"
0010
0011 #include "Acts/Definitions/Algebra.hpp"
0012 #include "Acts/Definitions/Common.hpp"
0013 #include "Acts/Surfaces/Surface.hpp"
0014 #include "Acts/Utilities/Result.hpp"
0015 #include "Acts/Utilities/UnitVectors.hpp"
0016
0017 Acts::FreeVector Acts::transformBoundToFreeParameters(
0018     const Acts::Surface& surface, const GeometryContext& geoCtx,
0019     const Acts::BoundVector& boundParams) {
0020   // convert angles to global unit direction vector
0021   Vector3 direction = makeDirectionFromPhiTheta(boundParams[eBoundPhi],
0022                                                 boundParams[eBoundTheta]);
0023
0024   // convert local position to global position vector
0025   Vector2 local(boundParams[eBoundLoc0], boundParams[eBoundLoc1]);
0026   Vector3 position = surface.localToGlobal(geoCtx, local, direction);
0027
0028   // construct full free-vector. time and q/p stay as-is.
0029   FreeVector freeParams = FreeVector::Zero();
0030   freeParams[eFreePos0] = position[ePos0];
0031   freeParams[eFreePos1] = position[ePos1];
0032   freeParams[eFreePos2] = position[ePos2];
0033   freeParams[eFreeTime] = boundParams[eBoundTime];
0034   freeParams[eFreeDir0] = direction[eMom0];
0035   freeParams[eFreeDir1] = direction[eMom1];
0036   freeParams[eFreeDir2] = direction[eMom2];
0037   freeParams[eFreeQOverP] = boundParams[eBoundQOverP];
0038   return freeParams;
0039 }
0040
0041 Acts::Result<Acts::BoundVector> Acts::transformFreeToBoundParameters(
0042     const FreeVector& freeParams, const Surface& surface,
0043     const GeometryContext& geoCtx, double tolerance) {
0044   // initialize the bound vector
0045   BoundVector bp = BoundVector::Zero();
0046   // convert global to local position on the surface
0047   auto position = freeParams.segment<3>(eFreePos0);
0048   auto direction = freeParams.segment<3>(eFreeDir0);
0049   auto result = surface.globalToLocal(geoCtx, position, direction, tolerance);
0050   if (!result.ok()) {
0051     return Result<Acts::BoundVector>::failure(result.error());
0052   }
0053
0054   auto localPosition = result.value();
0055   bp[eBoundLoc0] = localPosition[ePos0];
0056   bp[eBoundLoc1] = localPosition[ePos1];
0057
0058   bp[eBoundTime] = freeParams[eFreeTime];
0059   bp[eBoundPhi] = VectorHelpers::phi(direction);
0060   bp[eBoundTheta] = VectorHelpers::theta(direction);
0061   bp[eBoundQOverP] = freeParams[eFreeQOverP];
0062   return Result<Acts::BoundVector>::success(bp);
0063 }
0064
0065 Acts::Result<Acts::BoundVector> Acts::transformFreeToBoundParameters(
0066     const Acts::Vector3& position, double time, const Acts::Vector3& direction,
0067     double qOverP, const Acts::Surface& surface,
0068     const Acts::GeometryContext& geoCtx, double tolerance) {
0069   // initialize the bound vector
0070   BoundVector bp = BoundVector::Zero();
0071   // convert global to local position on the surface
0072   auto result = surface.globalToLocal(geoCtx, position, direction, tolerance);
0073   if (!result.ok()) {
0074     return Result<Acts::BoundVector>::failure(result.error());
0075   }
0076
0077   auto localPosition = result.value();
0078   bp[eBoundLoc0] = localPosition[ePos0];
0079   bp[eBoundLoc1] = localPosition[ePos1];
0080
0081   bp[eBoundTime] = time;
0082   bp[eBoundPhi] = VectorHelpers::phi(direction);
0083   bp[eBoundTheta] = VectorHelpers::theta(direction);
0084   bp[eBoundQOverP] = qOverP;
0085   return Result<Acts::BoundVector>::success(bp);
0086 }
0087
0088 Acts::BoundVector Acts::transformFreeToCurvilinearParameters(double time,
0089                                                              double phi,
0090                                                              double theta,
0091                                                              double qOverP) {
0092   BoundVector bp = BoundVector::Zero();
0093   // local coordinates are zero by construction
0094   bp[eBoundTime] = time;
0095   bp[eBoundPhi] = phi;
0096   bp[eBoundTheta] = theta;
0097   bp[eBoundQOverP] = qOverP;
0098   return bp;
0099 }
0100
0101 Acts::BoundVector Acts::transformFreeToCurvilinearParameters(
0102     double time, const Vector3& direction, double qOverP) {
0103   BoundVector bp = BoundVector::Zero();
0104   // local coordinates are zero by construction
0105   bp[eBoundTime] = time;
0106   bp[eBoundPhi] = VectorHelpers::phi(direction);
0107   bp[eBoundTheta] = VectorHelpers::theta(direction);
0108   bp[eBoundQOverP] = qOverP;
0109   return bp;
0110 }