From c506b43d49ac212388c2749d14a8acada4482021 Mon Sep 17 00:00:00 2001
From: Christophe Riccio <mail@g-truc.net>
Date: Thu, 12 Jun 2014 00:29:56 +0200
Subject: [PATCH] Quaternion vector rotation error. #209

---
 glm/gtc/quaternion.inl      |  8 ++++----
 test/gtc/gtc_quaternion.cpp | 11 +++++++++++
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/glm/gtc/quaternion.inl b/glm/gtc/quaternion.inl
index 9e926ee9..6396ea2e 100644
--- a/glm/gtc/quaternion.inl
+++ b/glm/gtc/quaternion.inl
@@ -302,11 +302,11 @@ namespace detail
 		detail::tvec3<T, P> const & v
 	)
 	{
-		detail::tvec3<T, P> u(q.x, q.y, q.z);
-		detail::tvec3<T, P> uv(glm::cross(u, v) * q.w);
-		detail::tvec3<T, P> uuv(glm::cross(u, uv));
+		detail::tvec3<T, P> const QuatVector(q.x, q.y, q.z);
+		detail::tvec3<T, P> const uv(glm::cross(QuatVector, v));
+		detail::tvec3<T, P> const uuv(glm::cross(QuatVector, uv));
 
-		return v + (uv + uuv) * static_cast<float>(2);
+		return v + ((uv * q.w) + uuv) * static_cast<T>(2);
 	}
 
 	template <typename T, precision P>
diff --git a/test/gtc/gtc_quaternion.cpp b/test/gtc/gtc_quaternion.cpp
index 4346e8fc..f56ad47e 100644
--- a/test/gtc/gtc_quaternion.cpp
+++ b/test/gtc/gtc_quaternion.cpp
@@ -247,6 +247,16 @@ int test_quat_type()
 	return 0;
 }
 
+int test_quat_mul_vec()
+{
+	glm::quat q = glm::angleAxis(glm::pi<float>() * 0.5f, glm::vec3(0, 0, 1));
+	glm::vec3 v(1, 0, 0);
+	glm::vec3 u(q * v);
+	glm::vec3 w(u * q);
+
+	return glm::all(glm::epsilonEqual(v, w, 0.01f));
+}
+
 int test_quat_ctr()
 {
 	int Error(0);
@@ -269,6 +279,7 @@ int main()
 	int Error(0);
 
 	Error += test_quat_ctr();
+	Error += test_quat_mul_vec();
 	Error += test_quat_two_axis_ctr();
 	Error += test_quat_mul();
 	Error += test_quat_precision();