Add volumeId to the GeoChildNodeWithTrf

GeoModelCore/GeoModelHelpers/GeoModelHelpers/getChildNodesWithTrf.h

@@ -7,6 +7,7 @@
 #include "GeoModelKernel/GeoVPhysVol.h"
 #include "GeoModelKernel/GeoDefinitions.h"
 
+#include <optional>
 
 class GeoVolumeCursor;
 
@@ -27,9 +28,10 @@ struct GeoChildNodeWithTrf {
         bool isAlignable{false};
         /// @brief tag whether the physical volume is a full physVol
         bool isSensitive{false};
-
+        /// @brief Identifier of the volume. If there's any and no copies are active
+        std::optional<int> volumeId{std::nullopt};
         GeoChildNodeWithTrf() = default;
-        GeoChildNodeWithTrf(GeoVolumeCursor& curs);
+        GeoChildNodeWithTrf(GeoVolumeCursor& curs);      
 };
 
 /*** @brief Returns all direct children of a volume with their transform. Equicalent volumes can be summarized.

GeoModelCore/GeoModelHelpers/src/getChildNodesWithTrf.cxx

 /*
-  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
 */
 #include <utility>
 
@@ -20,11 +20,11 @@ namespace {
     volume{curs.getVolume()},
     nodeName{curs.getName()},
     isAlignable{curs.hasAlignableTransform()},
-    isSensitive{typeid(*volume) == typeid(GeoFullPhysVol)} {
+    isSensitive{typeid(*volume) == typeid(GeoFullPhysVol)},
+    volumeId{static_cast<const std::optional<int>&>(curs.getId())} {
     //// Do not specify a node name if it's a dummy one
     if (nodeName == dummyNodeName) {
         nodeName = volume->getLogVol()->getName();
-
     }
 }
 
@@ -53,6 +53,7 @@ std::vector <GeoChildNodeWithTrf> getChildrenWithRef(PVConstLink physVol,
             children.emplace_back(std::move(currentChild));
          } else if (prevChild.nCopies == 1) {
             ++prevChild.nCopies;
+            prevChild.volumeId = std::nullopt;
             prevChild.inductionRule = prevChild.transform.inverse() * 
                                       currentChild.transform;            
          } else if (!transSort.compare(prevChild.inductionRule,