From 0675da467ac4680a9c2f22b3dfb3769df3c66896 Mon Sep 17 00:00:00 2001
From: Christophe Riccio <christopheri@unity3d.com>
Date: Sat, 24 Sep 2016 10:46:46 +0200
Subject: [PATCH] Optimized quaternion log function #554

---
 glm/gtx/quaternion.inl | 4 ++--
 readme.md              | 3 +++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/glm/gtx/quaternion.inl b/glm/gtx/quaternion.inl
index 1a31e947..c86ec187 100644
--- a/glm/gtx/quaternion.inl
+++ b/glm/gtx/quaternion.inl
@@ -71,9 +71,9 @@ namespace glm
 		}
 		else
 		{
-			T QuatLen = sqrt(Vec3Len * Vec3Len + q.w * q.w);
 			T t = atan(Vec3Len, T(q.w)) / Vec3Len;
-			return tquat<T, P>(log(QuatLen), t * q.x, t * q.y, t * q.z);
+			T QuatLen2 = Vec3Len * Vec3Len + q.w * q.w;
+			return tquat<T, P>(static_cast<T>(0.5) * log(QuatLen2), t * q.x, t * q.y, t * q.z);
 		}
 	}
 
diff --git a/readme.md b/readme.md
index f71333b9..efe14e2a 100644
--- a/readme.md
+++ b/readme.md
@@ -52,6 +52,9 @@ glm::mat4 camera(float Translate, glm::vec2 const & Rotate)
 ## Release notes
 
 #### [GLM 0.9.8.1](https://github.com/g-truc/glm/tree/0.9.8) - 2016-XX-XX
+##### Improvements:
+- Optimized quaternion log function #554
+
 ##### Fixes:
 - Fixed GCC warning filtering, replaced -pedantic by -Wpedantic
 - Fixed SIMD faceforward bug. #549