From a6ba5f18950f8471c5f3c168a9d65e901a8a6f2a Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Wed, 22 May 2013 22:48:45 +0300
Subject: [PATCH] Fix a case in ExtrudedShape with certain ray parameters

A ray starting outside of the length of the shape and pointing away from
it caused a local ray with a negative limit to be constructed.
---
 source/geometry/extrudedshape.h | 40 ++++++++++++++++++---------------
 1 file changed, 22 insertions(+), 18 deletions(-)

diff --git a/source/geometry/extrudedshape.h b/source/geometry/extrudedshape.h
index de582e3..c00111a 100644
--- a/source/geometry/extrudedshape.h
+++ b/source/geometry/extrudedshape.h
@@ -125,28 +125,32 @@ inline unsigned ExtrudedShape<T, D>::get_intersections(const Ray<T, D> &ray, Sur
 			if(offset<T(0))
 				offset = T(0);
 		}
-		T distortion = base_dir.norm();
-		Ray<T, D-1> base_ray(LinAl::Vector<T, D-1>(ray_start+ray_direction*offset),
-			base_dir, (limit-offset)*distortion);
-
-		SurfacePoint<T, D-1> *base_points = 0;
-		if(points)
-			/* Shamelessly reuse the provided storage.  Align to the end of the array
-			so processing can start from the first (nearest) point. */
-			base_points = reinterpret_cast<SurfacePoint<T, D-1> *>(points+size)-size;
-
-		unsigned count = base->get_intersections(base_ray, base_points, size);
-		for(unsigned i=0; (n<size && i<count); ++i)
+
+		if(limit>=offset)
 		{
+			T distortion = base_dir.norm();
+			Ray<T, D-1> base_ray(LinAl::Vector<T, D-1>(ray_start+ray_direction*offset),
+				base_dir, (limit-offset)*distortion);
+
+			SurfacePoint<T, D-1> *base_points = 0;
 			if(points)
+				/* Shamelessly reuse the provided storage.  Align to the end of the array
+				so processing can start from the first (nearest) point. */
+				base_points = reinterpret_cast<SurfacePoint<T, D-1> *>(points+size)-size;
+
+			unsigned count = base->get_intersections(base_ray, base_points, size);
+			for(unsigned i=0; (n<size && i<count); ++i)
 			{
-				T x = offset+base_points[i].distance/distortion;
-				points[n].position = ray_start+ray_direction*x;
-				points[n].normal = LinAl::Vector<T, D>(base_points[i].normal, T(0));
-				points[n].distance = x;
-			}
+				if(points)
+				{
+					T x = offset+base_points[i].distance/distortion;
+					points[n].position = ray_start+ray_direction*x;
+					points[n].normal = LinAl::Vector<T, D>(base_points[i].normal, T(0));
+					points[n].distance = x;
+				}
 
-			++n;
+				++n;
+			}
 		}
 	}
 
-- 
2.43.0