From a7dab4e68c022b039b0f4f8ca2b3e58c4b74aa59 Mon Sep 17 00:00:00 2001
From: Patrick Shriwise <pshriwise@gmail.com>
Date: Fri, 25 Jun 2021 06:39:49 -0500
Subject: [PATCH] Adding comment on DAGMC indices.

---
 src/dagmc.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/dagmc.cpp b/src/dagmc.cpp
index 5932e04a1..1132681a5 100644
--- a/src/dagmc.cpp
+++ b/src/dagmc.cpp
@@ -245,7 +245,7 @@ DAGUniverse::initialize() {
 
     // set cell ids using global IDs
     auto s = std::make_unique<DAGSurface>();
-    s->dag_index_ = i+1;
+    s->dag_index_ = i+1; // DAGMC indices start at 1
     s->id_ = adjust_geometry_ids_ ? next_surf_id++ : dagmc_instance_->id_by_index(2, i+1);
     s->dagmc_ptr_ = dagmc_instance_;