diff --git a/network_process/src/connect_by_topo/patch_connectivity.cpp b/network_process/src/connect_by_topo/patch_connectivity.cpp
index bd2e75e..35a59fc 100644
--- a/network_process/src/connect_by_topo/patch_connectivity.cpp
+++ b/network_process/src/connect_by_topo/patch_connectivity.cpp
@@ -82,12 +82,12 @@ void compute_patches(const stl_vector_mp<stl_vector_mp<edge_key_t>>&    edges_of
     }
 }
 
-void compute_chains(const flat_hash_map_mp<edge_key_t, edge_header_t>&   patch_edges,
-                    const flat_hash_set_mp<edge_key_t>&                  patch_boundary_edges,
-                    const stl_vector_mp<polygon_face_t>&                 iso_faces,
-                    stl_vector_mp<stl_vector_mp<uint32_t>>&              chain_vertices,
-                    stl_vector_mp<boundary_edge_header_t>&               chain_edge_headers,
-                    stl_vector_mp<chain_header_t>&                       chain_headers)
+void compute_chains(const flat_hash_map_mp<edge_key_t, edge_header_t>& patch_edges,
+                    const flat_hash_set_mp<edge_key_t>&                patch_boundary_edges,
+                    const stl_vector_mp<polygon_face_t>&               iso_faces,
+                    stl_vector_mp<stl_vector_mp<uint32_t>>&            chain_vertices,
+                    stl_vector_mp<boundary_edge_header_t>&             chain_edge_headers,
+                    stl_vector_mp<chain_header_t>&                     chain_headers)
 {
     flat_hash_map_mp<uint32_t, stl_vector_mp<uint32_t>> non_manifold_edges_of_vert{};
     non_manifold_edges_of_vert.reserve(patch_boundary_edges.size() / 2);
@@ -117,10 +117,7 @@ void compute_chains(const flat_hash_map_mp<edge_key_t, edge_header_t>&   patch_e
             flat_hash_set_mp<uint32_t> unique_volume_indices{};
             new_chain_edge_headers.subface_indices.reserve(new_chain_headers.face_indices.size());
             for (const auto& face_index : new_chain_headers.face_indices) {
-                std::transform(iso_faces[face_index].headers.begin(),
-                               iso_faces[face_index].headers.end(),
-                               std::back_inserter(unique_volume_indices),
-                               [](const face_header_t& header) { return header.volume_index; });
+                for (const auto& [volume_index, _] : iso_faces[face_index].headers) unique_volume_indices.emplace(volume_index);
                 new_chain_edge_headers.subface_indices.emplace_back(iso_faces[face_index].subface_index);
             }
             std::move(unique_volume_indices.begin(),
diff --git a/network_process/src/post_topo/map_chains.cpp b/network_process/src/post_topo/map_chains.cpp
index 6723e77..15c1b23 100644
--- a/network_process/src/post_topo/map_chains.cpp
+++ b/network_process/src/post_topo/map_chains.cpp
@@ -22,7 +22,8 @@ void map_chain_to_parameteric_plane(const baked_blobtree_t&
     stl_vector_mp<uint32_t>              unique_chain_indices{};
     flat_hash_map_mp<uint32_t, uint32_t> old_chain_index_to_unique_index{};
     auto                                 unique_end_iter = unique_chain_indices.begin();
-    for (const auto& [subface_index, patch_indices] : patch_of_subface) {
+    for (const auto& [subface_index_, patch_indices] : patch_of_subface) {
+        const auto  subface_index               = subface_index_;
         const auto& subface                     = subfaces[subface_index].object_ptr.get();
         auto        mapping_func                = subface.fetch_param_mapping_evaluator();
         auto&       parameteric_plane           = parameteric_planes[subface_index];
@@ -62,7 +63,11 @@ void map_chain_to_parameteric_plane(const baked_blobtree_t&
             chain_vertex_flags_[0]                = chain_end_vertex_signular_flag[2 * chain_index];
             chain_vertex_flags_[chain.size() - 1] = chain_end_vertex_signular_flag[2 * chain_index + 1];
 
-            chain_other_subface_indices.emplace_back(chain_edge_headers[chain_index].subface_indices);
+            const auto& subface_indices     = chain_edge_headers[chain_index].subface_indices;
+            const auto  other_subface_index = *std::find_if_not(subface_indices.begin(),
+                                                               subface_indices.end(),
+                                                               [&](uint32_t index) { return index == subface_index; });
+            chain_other_subface_indices.emplace_back(other_subface_index);
         }
 
         for (const auto& patch_index : patch_indices) {