Resolve "Implement ci_GEM"

Closes #20 (closed)

src/ci_GEM.cpp

+#include <XML/Helper.h>
+///////////////////////////
+// Central Ion GEM
+///////////////////////////
+
+using namespace dd4hep;
+
+static Ref_t createDetector(Detector& desc, xml_h handle, SensitiveDetector sens)
+{
+  xml::DetElement detElem = handle;
+  std::string     detName = detElem.nameStr();
+  int             detID   = detElem.id();
+
+  xml::Component dims = detElem.dimensions();
+  double SizeZ  = dims.sizez();     // Size in Z direction
+  double ROut   = dims.rmax();  // Outer radius
+  double RIn    = dims.rmin();  // Inner radius
+  double ShiftZ = dims.delta();
+  double PosX   = dims.posx();
+  double PosZ   = dims.posz();
+  int Nlayers   = dims.nlayers();
+  Material mat  = desc.material(detElem.materialStr());
+
+  Tube envelope(RIn, ROut, SizeZ, 0, 360 * deg);
+  //Volume envelopeVol(detName + "_envelope", envelope, det.;
+  
+  Tube   ci_GEM_GVol_Solid(RIn, ROut, SizeZ / 2., 0., 360 * deg);
+  Volume detVol("ci_GEM_GVol_Logic", ci_GEM_GVol_Solid, mat);
+
+  
+  for (cml_coll_t c(detElem, _U(layer)); c; c++)
+  {
+  	xml_comp_t x_layer = c;
+  	string layer_name = detName + _toString(c.id(), "_layer%d");
+  	Volume layer_vol(layer_name, Tube(c.rmin(), c.rmax(), c.z() ), mat );
+  	Position layer_pos(0, 0, fnz);
+  	pv = envelopeVol.placeVolume(layer_vol, layer_pos);
+  	pv.addPhysVolID("layer", c.id() );
+  }
+
+
+
+  detVol.setVisAttributes(desc.visAttributes(detElem.visStr()));
+
+  DetElement   det(detName, detID);
+  Volume       motherVol = desc.pickMotherVolume(det);
+  Transform3D  tr(RotationZYX(0., 0., 0.), Position(0., 0., ShiftZ));
+  PlacedVolume detPV = motherVol.placeVolume(envelopeVol, tr);
+  det.setPlacement(detPV);
+  return det;
+}
+// clang-format off
+DECLARE_DETELEMENT(ci_GEM, createDetector)