From 6f61bb4d2edbbb6b79fcb11596e91ceae48cae8c Mon Sep 17 00:00:00 2001
From: Olivier Sohn <olivier.sohn@gmail.com>
Date: Sat, 21 Oct 2017 21:17:55 +0200
Subject: [PATCH 1/3] Fix rotation when vectors are in the same direction #690

---
 glm/gtx/quaternion.inl | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/glm/gtx/quaternion.inl b/glm/gtx/quaternion.inl
index 5595ec38..f57082fa 100644
--- a/glm/gtx/quaternion.inl
+++ b/glm/gtx/quaternion.inl
@@ -184,8 +184,10 @@ namespace glm
 		T cosTheta = dot(orig, dest);
 		vec<3, T, Q> rotationAxis;
 
-		if(cosTheta >= static_cast<T>(1) - epsilon<T>())
-			return quat();
+		if(cosTheta >= static_cast<T>(1) - epsilon<T>()) {
+			// orig and dest point in the same direction : return identity quaternion.
+			return quat(1, 0, 0, 0);
+		}
 
 		if(cosTheta < static_cast<T>(-1) + epsilon<T>())
 		{

From 6bd81b8fbc1038d1c8c7f6fb2c582a89673e9891 Mon Sep 17 00:00:00 2001
From: Olivier Sohn <olivier.sohn@gmail.com>
Date: Sat, 21 Oct 2017 21:43:47 +0200
Subject: [PATCH 2/3] use quat_identity

---
 glm/gtx/quaternion.inl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/glm/gtx/quaternion.inl b/glm/gtx/quaternion.inl
index f57082fa..b99b869f 100644
--- a/glm/gtx/quaternion.inl
+++ b/glm/gtx/quaternion.inl
@@ -185,8 +185,8 @@ namespace glm
 		vec<3, T, Q> rotationAxis;
 
 		if(cosTheta >= static_cast<T>(1) - epsilon<T>()) {
-			// orig and dest point in the same direction : return identity quaternion.
-			return quat(1, 0, 0, 0);
+			// orig and dest point in the same direction
+			return quat_identity();
 		}
 
 		if(cosTheta < static_cast<T>(-1) + epsilon<T>())

From ddb93dcdc2b4af4b5bac7f4905c3108fad7fc78b Mon Sep 17 00:00:00 2001
From: Olivier Sohn <olivier.sohn@gmail.com>
Date: Sat, 21 Oct 2017 21:50:36 +0200
Subject: [PATCH 3/3] fix build

---
 glm/gtx/quaternion.inl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/glm/gtx/quaternion.inl b/glm/gtx/quaternion.inl
index b99b869f..b29b53d8 100644
--- a/glm/gtx/quaternion.inl
+++ b/glm/gtx/quaternion.inl
@@ -186,7 +186,7 @@ namespace glm
 
 		if(cosTheta >= static_cast<T>(1) - epsilon<T>()) {
 			// orig and dest point in the same direction
-			return quat_identity();
+			return quat_identity<T,Q>();
 		}
 
 		if(cosTheta < static_cast<T>(-1) + epsilon<T>())