From aa24f27d4d514893c028dfaef319e08b445675fe Mon Sep 17 00:00:00 2001
From: "Labossiere-Hickman, Travis James" <Travis.LabossiereHickman@inl.gov>
Date: Thu, 16 Jul 2026 15:47:49 -0600
Subject: [PATCH] Remove mesh labeling from MeshSurfaceFilter

---
 include/openmc/tallies/filter_meshsurface.h | 15 -------
 src/tallies/filter_meshsurface.cpp          | 48 +++------------------
 2 files changed, 5 insertions(+), 58 deletions(-)

diff --git a/include/openmc/tallies/filter_meshsurface.h b/include/openmc/tallies/filter_meshsurface.h
index 195995c69..fc6915200 100644
--- a/include/openmc/tallies/filter_meshsurface.h
+++ b/include/openmc/tallies/filter_meshsurface.h
@@ -22,21 +22,6 @@ public:
   // Accessors
 
   void set_mesh(int32_t mesh) override;
-
-  enum class MeshDir {
-    OUT_LEFT,   // x min
-    IN_LEFT,    // x min
-    OUT_RIGHT,  // x max
-    IN_RIGHT,   // x max
-    OUT_BACK,   // y min
-    IN_BACK,    // y min
-    OUT_FRONT,  // y max
-    IN_FRONT,   // y max
-    OUT_BOTTOM, // z min
-    IN_BOTTOM,  // z min
-    OUT_TOP,    // z max
-    IN_TOP      // z max
-  };
 };
 
 } // namespace openmc
diff --git a/src/tallies/filter_meshsurface.cpp b/src/tallies/filter_meshsurface.cpp
index b26cd198b..46626977b 100644
--- a/src/tallies/filter_meshsurface.cpp
+++ b/src/tallies/filter_meshsurface.cpp
@@ -28,52 +28,14 @@ std::string MeshSurfaceFilter::text_label(int bin) const
   auto& mesh = *model::meshes[mesh_];
   int n_dim = mesh.n_dimension_;
 
-  // Get flattend mesh index and surface index.
+  // Get flattened mesh index and surface index.
   int i_mesh = bin / (4 * n_dim);
-  MeshDir surf_dir = static_cast<MeshDir>(bin % (4 * n_dim));
+  int surf_index = bin % (4 * n_dim);
 
-  // Get mesh index part of label.
+  // Get mesh index part of label, then append the surface part. 
+  // The surface is labeled by the underlying mesh.
   std::string out = MeshFilter::text_label(i_mesh);
-
-  // Get surface part of label.
-  switch (surf_dir) {
-  case MeshDir::OUT_LEFT:
-    out += " Outgoing, x-min";
-    break;
-  case MeshDir::IN_LEFT:
-    out += " Incoming, x-min";
-    break;
-  case MeshDir::OUT_RIGHT:
-    out += " Outgoing, x-max";
-    break;
-  case MeshDir::IN_RIGHT:
-    out += " Incoming, x-max";
-    break;
-  case MeshDir::OUT_BACK:
-    out += " Outgoing, y-min";
-    break;
-  case MeshDir::IN_BACK:
-    out += " Incoming, y-min";
-    break;
-  case MeshDir::OUT_FRONT:
-    out += " Outgoing, y-max";
-    break;
-  case MeshDir::IN_FRONT:
-    out += " Incoming, y-max";
-    break;
-  case MeshDir::OUT_BOTTOM:
-    out += " Outgoing, z-min";
-    break;
-  case MeshDir::IN_BOTTOM:
-    out += " Incoming, z-min";
-    break;
-  case MeshDir::OUT_TOP:
-    out += " Outgoing, z-max";
-    break;
-  case MeshDir::IN_TOP:
-    out += " Incoming, z-max";
-    break;
-  }
+  out += mesh.surface_bin_label(surf_index);
 
   return out;
 }