From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 2 Jul 2016 17:00:50 +0000 (+0300)
Subject: Ensure that HyperBox does not produce duplicate intersections
X-Git-Url: http://git.tdb.fi/?p=libs%2Fmath.git;a=commitdiff_plain;h=818f9df5f383adad815f6f3276bfc1fa30c25681

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.
---

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;