diff --git a/network_process/src/post_topo/patch_propagation.cpp b/network_process/src/post_topo/patch_propagation.cpp
index 68ce1fb..79afb56 100644
--- a/network_process/src/post_topo/patch_propagation.cpp
+++ b/network_process/src/post_topo/patch_propagation.cpp
@@ -137,9 +137,12 @@ void transform_subface_to_primitive_labels(const baked_blobtree_t&
         temp_subface_signs.reserve(subface_indices.size());
         for (const auto& subface_index : subface_indices) 
             temp_subface_signs.emplace_back(cell_subface_signs[subface_index]);
-
+        // sign 0 in blobtree means inside, so we need to flip the sign
         cell_primitive_sign = primitive.judge_sign_by_subface_sign(temp_subface_signs);
         std::cout << "primitive " << i << " sign: " << cell_primitive_sign << std::endl;
+        for (size_t j = 0; j < cell_primitive_sign.size(); ++j) {
+            std::cout << "  subface sign for cell " << j << ": " << cell_primitive_sign[j] << std::endl;
+        }
     }
 }