From 955c04deaa6c6d1208bdd14c9a819e8b5f18d31b Mon Sep 17 00:00:00 2001
From: Jan Ellmenreich <jan.ellmenreich@outlook.com>
Date: Fri, 19 Sep 2025 14:53:30 +0200
Subject: [PATCH] [ADD] Copy identifications when extracting submesh

---
 libsrc/meshing/meshclass.cpp | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/libsrc/meshing/meshclass.cpp b/libsrc/meshing/meshclass.cpp
index 6e1faf08..3f4ac514 100644
--- a/libsrc/meshing/meshclass.cpp
+++ b/libsrc/meshing/meshclass.cpp
@@ -7323,7 +7323,7 @@ namespace netgen
   {
     // Copy the mesh into a new one, then delete unwanted elements
     // Unused points are deleted by the Compress() function at the end
-    auto mesh_ptr = make_unique<Mesh>();
+    auto mesh_ptr = make_shared<Mesh>();
     auto & mesh = *mesh_ptr;
     mesh = (*this);
 
@@ -7401,6 +7401,14 @@ namespace netgen
       if(!keep_point[pel.pnum])
         mesh.pointelements.DeleteElement(npointelements-i-1);
     }
+  
+    // Copy identifications to submesh. Redundant identifications are removed in Compress()
+    auto & ident_to = mesh.GetIdentifications();
+    const auto & ident_from = this->GetIdentifications();
+    for(const auto pair : ident_from.GetPairs())
+    {
+      ident_to.Add(pair.I1(), pair.I2(), ident_from.GetName(pair.I3()), ident_from.GetType(pair.I3()));
+    }
 
     mesh.Compress();
     return mesh_ptr;