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] 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>())
 		{