DDCutTubsFromPoints.cc

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// File: DDCutTubsFromPoints.cc
// Description: Create a ring of CutTubs segments from points on the rim.

#include "FWCore/MessageLogger/interface/MessageLogger.h"
#include "DetectorDescription/Core/interface/DDCurrentNamespace.h"
#include "DetectorDescription/Core/interface/DDSolid.h"
#include "DetectorDescription/Core/interface/DDVector.h"
#include "DetectorDescription/Core/interface/DDTypes.h"
#include "DetectorDescription/Core/interface/DDAlgorithm.h"
#include "DetectorDescription/Core/interface/DDAlgorithmFactory.h"
#include "DetectorDescription/Core/interface/DDMaterial.h"
#include <CLHEP/Units/GlobalPhysicalConstants.h>
#include <CLHEP/Units/SystemOfUnits.h>

#include <cmath>
#include <map>
#include <string>
#include <vector>

// This algorithm creates a ring made of CutTubs segments from the phi,z points
// of the rings "corners".
// The algorithm only defines and places two copies of a single Solid with the given name.
class DDCutTubsFromPoints : public DDAlgorithm {
public:
  //Constructor and Destructor
  DDCutTubsFromPoints();
  ~DDCutTubsFromPoints() override;

  void initialize(const DDNumericArguments& nArgs,
                  const DDVectorArguments& vArgs,
                  const DDMapArguments& mArgs,
                  const DDStringArguments& sArgs,
                  const DDStringVectorArguments& vsArgs) override;

  void execute(DDCompactView& cpv) override;

private:
  struct Section {
    double phi;  // phi position of this edge
    double z_l;  // -Z end (cuttubs l plane)
    double z_t;  // +Z end (cuttubs t plane)
    // radius is implicitly r_min
  };

  double r_min;
  double r_max;
  double z_pos;
  DDMaterial material;

  // a segment is produced between each two consecutive sections that have a
  // non-zero phi distance. Sections with zero phi distance can be used to
  // create sharp jumps.
  std::vector<Section> sections;
  // this solid will be defined.
  DDName solidOutput;
};

DDCutTubsFromPoints::DDCutTubsFromPoints() {
  LogDebug("TrackerGeom") << "DDCutTubsFromPoints info: Creating an instance";
}

DDCutTubsFromPoints::~DDCutTubsFromPoints() {}

void DDCutTubsFromPoints::initialize(const DDNumericArguments& nArgs,
                                     const DDVectorArguments& vArgs,
                                     const DDMapArguments&,
                                     const DDStringArguments& sArgs,
                                     const DDStringVectorArguments&) {
  r_min = nArgs["rMin"];
  r_max = nArgs["rMax"];
  z_pos = nArgs["zPos"];
  material = DDMaterial(sArgs["Material"]);

  auto phis_name = DDName(sArgs["Phi"]);
  auto z_ls_name = DDName(sArgs["z_l"]);
  auto z_ts_name = DDName(sArgs["z_t"]);
  DDVector phis(phis_name);
  DDVector z_ls(z_ls_name);
  DDVector z_ts(z_ts_name);

  assert(phis.size() == z_ls.size());
  assert(phis.size() == z_ts.size());

  for (unsigned i = 0; i < phis.size(); i++) {
    Section s = {phis[i], z_ls[i], z_ts[i]};
    sections.emplace_back(s);
  }
  assert(!sections.empty());

  solidOutput = DDName(sArgs["SolidName"]);

  std::string idNameSpace = DDCurrentNamespace::ns();
  DDName parentName = parent().name();
  LogDebug("TrackerGeom") << "DDCutTubsFromPoints debug: Parent " << parentName << "\tSolid " << solidOutput
                          << " NameSpace " << idNameSpace << "\tnumber of sections " << sections.size();
}

static double square(double x) { return x * x; }

void DDCutTubsFromPoints::execute(DDCompactView& cpv) {
  // radius for plane calculations
  // We use r_max here, since P3 later has a Z that is always more inside
  // than the extreme points. This means the cutting planes have outwards
  // slopes in r-Z, and the corner at r_max could stick out of the bounding
  // volume otherwise.
  double r = r_max;

  // min and max z for the placement in the end
  double min_z = 1e9;
  double max_z = -1e9;

  // counter of actually produced segments (excluding skipped ones)
  int segment = 0;

  // the segments and their corresponding offset (absolute, as in the input)
  std::vector<DDSolid> segments;
  std::vector<double> offsets;

  Section s1 = sections[0];
  for (Section s2 : sections) {
    if (s1.phi != s2.phi) {
      segment++;
      // produce segment s1-s2.
      DDName segname(solidOutput.name() + "_seg_" + std::to_string(segment), solidOutput.ns());

      double phi1 = s1.phi;
      double phi2 = s2.phi;

      // track the min/max to properly place&align later
      if (s2.z_l < min_z)
        min_z = s2.z_l;
      if (s2.z_t > max_z)
        max_z = s2.z_t;

      double P1_z_l = s1.z_l;
      double P1_z_t = s1.z_t;
      double P2_z_l = s2.z_l;
      double P2_z_t = s2.z_t;

      double P1_x_t = cos(phi1) * r;
      double P1_x_l = cos(phi1) * r;
      double P1_y_t = sin(phi1) * r;
      double P1_y_l = sin(phi1) * r;

      double P2_x_t = cos(phi2) * r;
      double P2_x_l = cos(phi2) * r;
      double P2_y_t = sin(phi2) * r;
      double P2_y_l = sin(phi2) * r;

      // each cutting plane is defined by P1-3. P1-2 are corners of the
      // segment, P3 is at r=0 with the "average" z to get a nice cut.
      double P3_z_l = (P1_z_l + P2_z_l) / 2;
      double P3_z_t = (P1_z_t + P2_z_t) / 2;

      // we only have one dz to position both planes. The anchor is implicitly
      // between the P3's, we have to use an offset later to make the segments
      // line up correctly.
      double dz = (P3_z_t - P3_z_l) / 2;
      double offset = (P3_z_t + P3_z_l) / 2;

      // the plane is defined by P1-P3 and P2-P3; since P3 is at r=0 we
      // only need the z.
      double D1_z_l = P1_z_l - P3_z_l;
      double D2_z_l = P2_z_l - P3_z_l;

      // the normal is then the cross product...
      double n_x_l = (P1_y_l * D2_z_l) - (D1_z_l * P2_y_l);
      double n_y_l = (D1_z_l * P2_x_l) - (P1_x_l * D2_z_l);
      double n_z_l = (P1_x_l * P2_y_l) - (P1_y_l * P2_x_l);

      // ... normalized.
      // flip the sign here (but not for t) since root wants it like that.
      double norm = -sqrt(square(n_x_l) + square(n_y_l) + square(n_z_l));
      n_x_l /= norm;
      n_y_l /= norm;
      n_z_l /= norm;

      // same game for the t side.
      double D1_z_t = P1_z_t - P3_z_t;
      double D2_z_t = P2_z_t - P3_z_t;

      double n_x_t = (P1_y_t * D2_z_t) - (D1_z_t * P2_y_t);
      double n_y_t = (D1_z_t * P2_x_t) - (P1_x_t * D2_z_t);
      double n_z_t = (P1_x_t * P2_y_t) - (P1_y_t * P2_x_t);

      norm = sqrt(square(n_x_t) + square(n_y_t) + square(n_z_t));
      n_x_t /= norm;
      n_y_t /= norm;
      n_z_t /= norm;

      // the cuttubs wants a delta phi
      double dphi = phi2 - phi1;

      DDSolid seg =
          DDSolidFactory::cuttubs(segname, dz, r_min, r_max, phi1, dphi, n_x_l, n_y_l, n_z_l, n_x_t, n_y_t, n_z_t);
      segments.emplace_back(seg);
      offsets.emplace_back(offset);
    }
    s1 = s2;
  }

  assert(segments.size() >= 2);  // less would be special cases

  DDSolid solid = segments[0];
  // placment happens relative to the first member of the union
  double shift = offsets[0];

  for (unsigned i = 1; i < segments.size() - 1; i++) {
    // each sub-union needs a name. Well.
    DDName unionname(solidOutput.name() + "_uni_" + std::to_string(i + 1), solidOutput.ns());
    solid = DDSolidFactory::unionSolid(
        unionname, solid, segments[i], DDTranslation(0, 0, offsets[i] - shift), DDRotation());
  }

  solid = DDSolidFactory::unionSolid(solidOutput,
                                     solid,
                                     segments[segments.size() - 1],
                                     DDTranslation(0, 0, offsets[segments.size() - 1] - shift),
                                     DDRotation());

  // remove the common offset from the input, to get sth. aligned at z=0.
  double offset = -shift + (min_z + (max_z - min_z) / 2);

  DDLogicalPart logical(solidOutput, material, solid, DDEnums::support);

  // This is not as generic as the name promises, but it is hard to make a
  // solid w/o placing it.
  DDRotation rot180("pixfwdCommon:Z180");
  cpv.position(logical, parent(), 1, DDTranslation(0, 0, z_pos - offset), DDRotation());
  cpv.position(logical, parent(), 2, DDTranslation(0, 0, z_pos - offset), rot180);
}

DEFINE_EDM_PLUGIN(DDAlgorithmFactory, DDCutTubsFromPoints, "track:DDCutTubsFromPoints");