From 3760c8b5c4c22ec04266daededa0560d4c8a9349 Mon Sep 17 00:00:00 2001
From: Lynix <lynix680@gmail.com>
Date: Fri, 13 Dec 2019 17:23:01 +0100
Subject: [PATCH] Utility/Node: Fix negative scaling not affecting rotation

---
 ChangeLog.md                    |  1 +
 include/Nazara/Utility/Node.hpp |  2 ++
 src/Nazara/Utility/Node.cpp     | 35 +++++++++++++++++++++++++++++----
 3 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/ChangeLog.md b/ChangeLog.md
index f00da9c5f..00f8b937a 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -205,6 +205,7 @@ Nazara Engine:
 - ⚠ Removed all Set methods from math classes taking their own type (e.g. Box::Set(Box))
 - Added Matrix4::Decompose
 - ⚠ Node::Get[Position|Rotation|Scale] now defaults to local space
+- Fixed Node rotation when using a negative scale
 
 Nazara Development Kit:
 - Added ImageWidget (#139)
diff --git a/include/Nazara/Utility/Node.hpp b/include/Nazara/Utility/Node.hpp
index e4cb3cfb2..da36997ec 100644
--- a/include/Nazara/Utility/Node.hpp
+++ b/include/Nazara/Utility/Node.hpp
@@ -105,6 +105,8 @@ namespace Nz
 			virtual void UpdateDerived() const;
 			virtual void UpdateTransformMatrix() const;
 
+			static Quaternionf ScaleQuaternion(const Vector3f& scale, Quaternionf quaternion);
+
 			mutable std::vector<Node*> m_childs;
 			mutable Matrix4f m_transformMatrix;
 			mutable Quaternionf m_derivedRotation;
diff --git a/src/Nazara/Utility/Node.cpp b/src/Nazara/Utility/Node.cpp
index 2832df42d..c14c81d13 100644
--- a/src/Nazara/Utility/Node.cpp
+++ b/src/Nazara/Utility/Node.cpp
@@ -574,7 +574,7 @@ namespace Nz
 		if (!m_derivedUpdated)
 			UpdateDerived();
 
-		return m_derivedPosition + (m_derivedScale * (m_derivedRotation * localPosition));
+		return m_derivedPosition + (m_derivedScale * (ScaleQuaternion(m_derivedScale, m_derivedRotation) * localPosition));
 	}
 
 	Quaternionf Node::ToGlobalRotation(const Quaternionf& localRotation) const
@@ -582,7 +582,7 @@ namespace Nz
 		if (!m_derivedUpdated)
 			UpdateDerived();
 
-		return m_derivedRotation * localRotation;
+		return ScaleQuaternion(m_derivedScale, m_derivedRotation) * localRotation;
 	}
 
 	Vector3f Node::ToGlobalScale(const Vector3f& localScale) const
@@ -598,7 +598,7 @@ namespace Nz
 		if (!m_derivedUpdated)
 			UpdateDerived();
 
-		return (m_derivedRotation.GetConjugate()*(globalPosition - m_derivedPosition))/m_derivedScale;
+		return (m_derivedScale, m_derivedRotation.GetConjugate()*(globalPosition - m_derivedPosition))/m_derivedScale;
 	}
 
 	Quaternionf Node::ToLocalRotation(const Quaternionf& globalRotation) const
@@ -688,7 +688,11 @@ namespace Nz
 
 			if (m_inheritRotation)
 			{
-				m_derivedRotation = m_parent->m_derivedRotation * m_initialRotation * m_rotation;
+				Quaternionf rotation = m_initialRotation * m_rotation;
+				if (m_inheritScale)
+					rotation = ScaleQuaternion(m_parent->m_derivedScale, rotation);
+
+				m_derivedRotation = m_parent->m_derivedRotation * rotation;
 				m_derivedRotation.Normalize();
 			}
 			else
@@ -716,4 +720,27 @@ namespace Nz
 		m_transformMatrix.MakeTransform(m_derivedPosition, m_derivedRotation, m_derivedScale);
 		m_transformMatrixUpdated = true;
 	}
+
+	Quaternionf Node::ScaleQuaternion(const Vector3f& scale, Quaternionf quaternion)
+	{
+		if (std::signbit(scale.x))
+		{
+			quaternion.z = -quaternion.z;
+			quaternion.y = -quaternion.y;
+		}
+
+		if (std::signbit(scale.y))
+		{
+			quaternion.x = -quaternion.x;
+			quaternion.z = -quaternion.z;
+		}
+
+		if (std::signbit(scale.z))
+		{
+			quaternion.x = -quaternion.x;
+			quaternion.y = -quaternion.y;
+		}
+
+		return quaternion;
+	}
 }