From 818f9df5f383adad815f6f3276bfc1fa30c25681 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 2 Jul 2016 20:00:50 +0300
Subject: [PATCH] Ensure that HyperBox does not produce duplicate intersections

In certain corner cases (literally) two coincident intersections could be
produced when the ray passed through the edge of the box, preventing
intersctions on the opposite side from being produced.
---
 source/geometry/hyperbox.h | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/source/geometry/hyperbox.h b/source/geometry/hyperbox.h
index 546ad0e..b9fad33 100644
--- a/source/geometry/hyperbox.h
+++ b/source/geometry/hyperbox.h
@@ -112,14 +112,23 @@ inline unsigned HyperBox<T, D>::get_intersections(const Ray<T, D> &ray, SurfaceP
 			{
 				if(points)
 				{
-					points[n].position = p;
-					points[n].normal = LinAl::Vector<T, D>();
-					points[n].normal[i] = j;
-					points[n].distance = x;
-					points[n].entry = (T(j)*ray.get_direction()[i]<T(0));
-
-					if(n==1 && x<points[0].distance)
-						std::swap(points[0], points[1]);
+					bool entry = (T(j)*ray.get_direction()[i]<T(0));
+					unsigned k = 0;
+					if(n>0 && entry!=points[0].entry)
+					{
+						if(entry)
+							points[1] = points[0];
+						else
+							++k;
+					}
+					if(k<n && entry==points[k].entry)
+						--n;
+
+					points[k].position = p;
+					points[k].normal = LinAl::Vector<T, D>();
+					points[k].normal[i] = j;
+					points[k].distance = x;
+					points[k].entry = (T(j)*ray.get_direction()[i]<T(0));
 				}
 
 				++n;
-- 
2.43.0