From 17199ccfe701228d1a1bec0260b72ccd08c43a1d Mon Sep 17 00:00:00 2001
From: Dibyendu Majumdar <mobile@majumdar.org.uk>
Date: Sat, 9 May 2020 15:18:43 +0100
Subject: [PATCH] issue #7

---
 src/core/sys_source_point.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/core/sys_source_point.cpp b/src/core/sys_source_point.cpp
index a74bc0d..3cc4043 100644
--- a/src/core/sys_source_point.cpp
+++ b/src/core/sys_source_point.cpp
@@ -43,6 +43,7 @@ namespace _goptical {
     SourcePoint::SourcePoint(SourceInfinityMode m, const math::Vector3 &pos_dir)
       : Source(m == SourceAtInfinity
          // position of infinity source is only used for trace::Sequence sort
+		      // See https://lists.gnu.org/archive/html/goptical/2013-06/msg00004.html
                ? math::VectorPair3(pos_dir * -1e9, pos_dir)
                : math::VectorPair3(pos_dir, math::vector3_001)),
         _mode(m)