From b3f60e90fd05b6f05cf6a3c043e91372b31825d0 Mon Sep 17 00:00:00 2001
From: Lynix <lynix680@gmail.com>
Date: Thu, 30 May 2013 02:56:58 +0200
Subject: [PATCH] Fixed Quaternion::(Make)RotationBetween

Could not handle parallel vectors


Former-commit-id: 3fed3a46d443b208dc95a5bcd29dd43fb7960114
---
 include/Nazara/Math/Quaternion.inl | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/include/Nazara/Math/Quaternion.inl b/include/Nazara/Math/Quaternion.inl
index 4432eee21..ab843d4a1 100644
--- a/include/Nazara/Math/Quaternion.inl
+++ b/include/Nazara/Math/Quaternion.inl
@@ -132,13 +132,27 @@ NzQuaternion<T>& NzQuaternion<T>::MakeIdentity()
 template<typename T>
 NzQuaternion<T>& NzQuaternion<T>::MakeRotationBetween(const NzVector3<T>& from, const NzVector3<T>& to)
 {
-	NzVector3f a = from.CrossProduct(to);
-	x = a.x;
-	y = a.y;
-	z = a.z;
-	w = std::sqrt(std::pow(from.GetLength(), 2.f) * std::pow(to.GetLength(), 2.f)) + from.DotProduct(to);
+	T dot = from.DotProduct(to);
+	if (NzNumberEquals(dot, F(-1.0)))
+	{
+		NzVector3<T> cross = NzVector3<T>::CrossProduct(NzVector3<T>::UnitX(), from);
+		if (NzNumberEquals(cross.GetLength(), F(0.0)))
+			cross = NzVector3<T>::CrossProduct(NzVector3<T>::UnitY(), from);
 
-	return Normalize();
+		return Set(F(180.0), cross);
+	}
+	else if (NzNumberEquals(dot, F(1.0)))
+		return MakeIdentity();
+	else
+	{
+		NzVector3<T> a = from.CrossProduct(to);
+		x = a.x;
+		y = a.y;
+		z = a.z;
+		w = T(1.0) + dot;
+
+		return Normalize();
+	}
 }
 
 template<typename T>
@@ -195,12 +209,12 @@ NzQuaternion<T>& NzQuaternion<T>::Set(const T quat[4])
 template<typename T>
 NzQuaternion<T>& NzQuaternion<T>::Set(T angle, const NzVector3<T>& axis)
 {
-	angle *= F(0.5);
-
 	#if !NAZARA_MATH_ANGLE_RADIAN
 	angle = NzDegreeToRadian(angle);
 	#endif
 
+	angle *= F(0.5);
+
 	NzVector3<T> normalizedAxis = axis.GetNormal();
 
 	T sinAngle = std::sin(angle);