From 93ed76211eec2660c27b4e26d3099cb001f3529b Mon Sep 17 00:00:00 2001
From: Wenzel Jakob <wenzel@cs.cornell.edu>
Date: Tue, 22 Jan 2013 19:33:08 -0500
Subject: [PATCH] make intersection routines more robust vs NaNs

---
 src/emitters/constant.cpp | 2 +-
 src/shapes/cylinder.cpp   | 3 ++-
 src/shapes/disk.cpp       | 2 +-
 src/shapes/hair.cpp       | 4 ++--
 src/shapes/rectangle.cpp  | 2 +-
 src/shapes/sphere.cpp     | 3 ++-
 6 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/emitters/constant.cpp b/src/emitters/constant.cpp
index 3c391bf2..f1909c2d 100644
--- a/src/emitters/constant.cpp
+++ b/src/emitters/constant.cpp
@@ -196,7 +196,7 @@ public:
 		if (!m_sceneBSphere.rayIntersect(ray, nearT, farT))
 			return Spectrum(0.0f);
 
-		if (nearT >= 0 || farT <= 0)
+		if (!(nearT < 0 && farT > 0))
 			return Spectrum(0.0f);
 
 		dRec.p = ray(farT);
diff --git a/src/shapes/cylinder.cpp b/src/shapes/cylinder.cpp
index 83af281a..27139b0a 100644
--- a/src/shapes/cylinder.cpp
+++ b/src/shapes/cylinder.cpp
@@ -145,11 +145,12 @@ public:
 		if (!solveQuadratic(A, B, C, nearT, farT))
 			return false;
 
-		if (nearT > maxt || farT < mint)
+		if (!(nearT <= maxt && farT >= mint)) /* NaN-aware conditionals */
 			return false;
 
 		const Float zPosNear = ray.o.z + ray.d.z * nearT;
 		const Float zPosFar = ray.o.z + ray.d.z * farT;
+
 		if (zPosNear >= 0 && zPosNear <= m_length && nearT >= mint) {
 			t = nearT;
 		} else if (zPosFar >= 0 && zPosFar <= m_length) {
diff --git a/src/shapes/disk.cpp b/src/shapes/disk.cpp
index e4b2d429..fac35568 100644
--- a/src/shapes/disk.cpp
+++ b/src/shapes/disk.cpp
@@ -136,7 +136,7 @@ public:
 		m_worldToObject.transformAffine(_ray, ray);
 		Float hit = -ray.o.z / ray.d.z;
 
-		if (hit < mint || hit > maxt)
+		if (!(hit >= mint && hit <= maxt))
 			return false;
 
 		Point local = ray(hit);
diff --git a/src/shapes/hair.cpp b/src/shapes/hair.cpp
index b98b0eae..411b7db0 100644
--- a/src/shapes/hair.cpp
+++ b/src/shapes/hair.cpp
@@ -504,7 +504,7 @@ public:
 		if (!solveQuadraticDouble(A, B, C, nearT, farT))
 			return false;
 
-		if (nearT > maxt || farT < mint)
+		if (!(nearT <= maxt && farT >= mint)) /* NaN-aware conditionals */
 			return false;
 
 		/* Next check the intersection points against the miter planes */
@@ -523,7 +523,7 @@ public:
 			p = Point(rayO + rayD * nearT);
 			t = (Float) nearT;
 		} else if (dot(pointFar - v1, n1) >= 0 &&
-				dot(pointFar - v2, n2) <= 0) {
+		           dot(pointFar - v2, n2) <= 0) {
 			if (farT > maxt)
 				return false;
 			p = Point(rayO + rayD * nearT);
diff --git a/src/shapes/rectangle.cpp b/src/shapes/rectangle.cpp
index e5056a9e..553bbf17 100644
--- a/src/shapes/rectangle.cpp
+++ b/src/shapes/rectangle.cpp
@@ -127,7 +127,7 @@ public:
 		m_worldToObject.transformAffine(_ray, ray);
 		Float hit = -ray.o.z / ray.d.z;
 
-		if (hit < mint || hit > maxt)
+		if (!(hit >= mint && hit <= maxt))
 			return false;
 
 		Point local = ray(hit);
diff --git a/src/shapes/sphere.cpp b/src/shapes/sphere.cpp
index 0b644d19..522743e2 100644
--- a/src/shapes/sphere.cpp
+++ b/src/shapes/sphere.cpp
@@ -172,8 +172,9 @@ public:
 		if (!solveQuadraticDouble(A, B, C, nearT, farT))
 			return false;
 
-		if (nearT > maxt || farT < mint)
+		if (!(nearT <= maxt && farT >= mint)) /* NaN-aware conditionals */
 			return false;
+
 		if (nearT < mint) {
 			if (farT > maxt)
 				return false;