HelixBarrelPlaneCrossing2OrderLocal.cc

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#include "TrackingTools/GeomPropagators/interface/HelixBarrelPlaneCrossing2OrderLocal.h"
#include <algorithm>
#include <cmath>

HelixBarrelPlaneCrossing2OrderLocal::HelixBarrelPlaneCrossing2OrderLocal(const GlobalPoint& startingPos,
                                                                         const GlobalVector& startingDir,
                                                                         float rho,
                                                                         const Plane& plane) {
  typedef Basic2DVector<float> Vector2D;

  // translate problem to local frame of the plane
  Plane::ToLocal toLocal(plane);
  LocalPoint lPos = toLocal.toLocal(startingPos);
  LocalVector lDir = toLocal.toLocal(startingDir);

  // check if local frame is already special (local Y axis == global Z axis)
  LocalVector yPrime = toLocal.toLocal(GlobalVector(0, 0, 1.f));
  // LocalVector diff = yPrime - LocalVector(0,-1.f,0);
  float sinPhi = 0, cosPhi = 0;
  bool rotated;
  Vector2D pos;
  Vector2D dir;

  if (std::abs(yPrime.y()) > 0.9999f) {
    // cout << "Plane already oriented, yPrime = " << yPrime << endl;

    // we are already in the special orientation
    pos = Vector2D(lPos.x(), lPos.y());
    dir = Vector2D(lDir.x(), lDir.y());
    ;
    rotated = false;
  } else {
    // cout << "Plane needs rotation, yPrime = " << yPrime << endl;

    // we need to rotate the problem
    sinPhi = yPrime.y();
    cosPhi = yPrime.x();
    pos = Vector2D(lPos.x() * cosPhi + lPos.y() * sinPhi, -lPos.x() * sinPhi + lPos.y() * cosPhi);
    dir = Vector2D(lDir.x() * cosPhi + lDir.y() * sinPhi, -lDir.x() * sinPhi + lDir.y() * cosPhi);
    rotated = true;
  }

  float d = -lPos.z();
  float x = pos.x() + dir.x() / lDir.z() * d - 0.5f * rho * d * d;
  float y = pos.y() + dir.y() / lDir.z() * d;

  //    cout << "d= " << d << ", pos.x()= " << pos.x()
  //         << ", dir.x()/lDir.z()= " << dir.x()/lDir.z()
  //         << ", 0.5*rho*d*d= " << 0.5*rho*d*d << endl;

  if (!rotated) {
    thePos = LocalPoint(x, y, 0);
    theDir = LocalVector(dir.x() + rho * d, dir.y(), lDir.z());
  } else {
    thePos = LocalPoint(x * cosPhi - y * sinPhi, x * sinPhi + y * cosPhi, 0);
    float px = dir.x() + rho * d;
    theDir = LocalVector(px * cosPhi - dir.y() * sinPhi, px * sinPhi + dir.y() * cosPhi, lDir.z());
  }
}

LocalPoint HelixBarrelPlaneCrossing2OrderLocal::positionOnly(const GlobalPoint& startingPos,
                                                             const GlobalVector& startingDir,
                                                             float rho,
                                                             const Plane& plane) {
  typedef Basic2DVector<float> Vector2D;

  // translate problem to local frame of the plane
  Plane::ToLocal toLocal(plane);
  LocalPoint lPos = toLocal.toLocal(startingPos);
  LocalVector lDir = toLocal.toLocal(startingDir);

  // check if local frame is already special (local Y axis == global Z axis)
  LocalVector yPrime = toLocal.toLocal(GlobalVector(0, 0, 1.f));
  // LocalVector diff = yPrime - LocalVector(0,-1.f,0);
  float sinPhi = 0, cosPhi = 0;
  bool rotated;
  Vector2D pos;
  Vector2D dir;

  if (std::abs(yPrime.y()) > 0.9999f) {
    // cout << "Plane already oriented, yPrime = " << yPrime << endl;

    // we are already in the special orientation
    pos = Vector2D(lPos.x(), lPos.y());
    dir = Vector2D(lDir.x(), lDir.y());
    ;
    rotated = false;
  } else {
    // cout << "Plane needs rotation, yPrime = " << yPrime << endl;

    // we need to rotate the problem
    sinPhi = yPrime.y();
    cosPhi = yPrime.x();
    pos = Vector2D(lPos.x() * cosPhi + lPos.y() * sinPhi, -lPos.x() * sinPhi + lPos.y() * cosPhi);
    dir = Vector2D(lDir.x() * cosPhi + lDir.y() * sinPhi, -lDir.x() * sinPhi + lDir.y() * cosPhi);
    rotated = true;
  }

  float d = -lPos.z();
  float x = pos.x() + dir.x() / lDir.z() * d - 0.5f * rho * d * d;
  float y = pos.y() + dir.y() / lDir.z() * d;

  //    cout << "d= " << d << ", pos.x()= " << pos.x()
  //         << ", dir.x()/lDir.z()= " << dir.x()/lDir.z()
  //         << ", 0.5*rho*d*d= " << 0.5*rho*d*d << endl;

  return (!rotated) ? LocalPoint(x, y, 0) : LocalPoint(x * cosPhi - y * sinPhi, x * sinPhi + y * cosPhi, 0);
}