Working on ci_GEM, issues with constructing layers in volume

ci_GEM.xml

+<lccdd xmlns:compact="http://www.lcsim.org/schemas/compact/1.0" 
+       xmlns:xs="http://www.w3.org/2001/XMLSchema" 
+       xs:noNamespaceSchemaLocation="http://www.lcsim.org/schemas/compact/1.0/compact.xsd">
+>
+
+  <!-- Some information about detector  -->
+  <info name="Central Ion GEM" title="Central Ion GEM"
+        author="Marshall Scott"
+        url="https://eicweb.phy.anl.gov/EIC/detectors/reference_detector.git"
+        status="development"
+        version="v1 2021-03-23">
+    <comment>Central Ion GEM</comment>        
+  </info>
+
+  <!-- Use DD4hep elements and materials definitions -->
+  <includes>
+    <gdmlFile ref="elements.xml"/>
+    <gdmlFile ref="materials.xml"/>
+  </includes>
+
+  <!-- Define the dimensions of the world volume -->
+  <define>
+  	<constant name="world_side" value="50*m"/>
+  	<constant name="world_x"    value="world_side"/>
+    <constant name="world_y"    value="world_side"/>
+    <constant name="world_z"    value="world_side"/>
+
+    <constant name="ci_GEM_id"      value="1">
+    <constant name="ci_GEM_rin"     value="10 * cm">
+    <constant name="ci_GEM_rout"    value="95 * cm">
+    <constant name="ci_GEM_sizez"   value="30 * cm">
+    <constant name="ci_GEM_shiftz"  value="0 * cm">
+    <constant name="ci_GEM_posz"    value="0 * cm">
+    <constant name="ci_GEM_posx"    value="0 * cm">
+    <constant name="ci_GEM_nlayers" value="8">
+  </define>
+
+   <limits>
+  </limits>
+
+  <regions>
+  </regions>
+
+  <!-- Common Generic visualization attributes -->
+  <!-- change this -->
+  <comment>Common Generic visualization attributes</comment>
+  <display>
+    <vis name="ci_GEMVis" alpha="0.4"  r= "0.1"  g="0.0"  b="0.1"  showDaughters="true" visible="true"/>
+  </display>
+
+  <!-- Define detector -->
+  <detectors>
+    <comment>
+      Central Ion GEM
+    </comment>
+    <detector id="ci_GEM_id" name="ci_GEM" type="ci_GEM" insideTrackingVolume="false" vis="ci_GEMVis">
+	    <material name="Ar10CO2"/>  <!-- G4_Galactic -->	    
+      <dimensions rmin="ci_GEM_rin" rmax="ci_GEM_rout" sizez="ci_GEM_sizez" delta="ci_GEM_shiftz"	posz="ci_GEM_posz" posx="ci_GEM_posx" nlayers="ci_GEM_nlayers"/>
+      <layer id="0" z="-sizez * 0.5 + (5 + 3. * id) * cm" inner_r="rmin + (1. + 0.5 * id) * cm" outer_r="rmax + (-25. + 2. * id) * cm" dz="1 * cm" />
+      <layer id="1" z="-sizez * 0.5 + (5 + 3. * id) * cm" inner_r="rmin + (1. + 0.5 * id) * cm" outer_r="rmax + (-25. + 2. * id) * cm" dz="1 * cm" />
+      <layer id="2" z="-sizez * 0.5 + (5 + 3. * id) * cm" inner_r="rmin + (1. + 0.5 * id) * cm" outer_r="rmax + (-25. + 2. * id) * cm" dz="1 * cm" />
+      <layer id="3" z="-sizez * 0.5 + (5 + 3. * id) * cm" inner_r="rmin + (1. + 0.5 * id) * cm" outer_r="rmax + (-25. + 2. * id) * cm" dz="1 * cm" />
+      <layer id="4" z="-sizez * 0.5 + (5 + 3. * id) * cm" inner_r="rmin + (1. + 0.5 * id) * cm" outer_r="rmax + (-25. + 2. * id) * cm" dz="1 * cm" />
+      <layer id="5" z="-sizez * 0.5 + (5 + 3. * id) * cm" inner_r="rmin + (1. + 0.5 * id) * cm" outer_r="rmax + (-25. + 2. * id) * cm" dz="1 * cm" />
+      <layer id="6" z="-sizez * 0.5 + (5 + 3. * id) * cm" inner_r="rmin + (1. + 0.5 * id) * cm" outer_r="rmax + (-25. + 2. * id) * cm" dz="1 * cm" />
+      <layer id="7" z="-sizez * 0.5 + (5 + 3. * id) * cm" inner_r="rmin + (1. + 0.5 * id) * cm" outer_r="rmax + (-25. + 2. * id) * cm" dz="1 * cm" />
+    </detector>
+  </detectors>
+
+  <plugins>
+  </plugins>
+
+
+
+

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)