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diff --git a/extern/mantaflow/helper/util/quaternion.h b/extern/mantaflow/helper/util/quaternion.h
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+/******************************************************************************
+ *
+ * MantaFlow fluid solver framework
+ * Copyright 2011 Tobias Pfaff, Nils Thuerey
+ *
+ * This program is free software, distributed under the terms of the
+ * Apache License, Version 2.0
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Basic quaternion class
+ *
+ ******************************************************************************/
+
+#ifndef _QUATERNION_H
+#define _QUATERNION_H
+
+#include "vectorbase.h"
+
+namespace Manta {
+
+//! Very basic quaternion class
+class Quaternion {
+ public:
+  //! default constructor
+  Quaternion() : x(0), y(0), z(0), w(0)
+  {
+  }
+
+  //! copy constructor
+  Quaternion(const Quaternion &q) : x(q.x), y(q.y), z(q.z), w(q.w)
+  {
+  }
+
+  //! construct a quaternion from members
+  Quaternion(Real _x, Real _y, Real _z, Real _w) : x(_x), y(_y), z(_z), w(_w)
+  {
+  }
+
+  //! construct a quaternion from imag/real parts
+  Quaternion(Vec3 i, Real r) : x(i.x), y(i.y), z(i.z), w(r)
+  {
+  }
+
+  //! Assign operator
+  inline Quaternion &operator=(const Quaternion &q)
+  {
+    x = q.x;
+    y = q.y;
+    z = q.z;
+    w = q.w;
+    return *this;
+  }
+
+  //! Assign multiplication operator
+  inline Quaternion &operator*=(const Real a)
+  {
+    x *= a;
+    y *= a;
+    z *= a;
+    w *= a;
+    return *this;
+  }
+
+  //! return inverse quaternion
+  inline Quaternion inverse() const
+  {
+    Real mag = 1.0 / (x * x + y * y + z * z + w * w);
+    return Quaternion(-x * mag, -y * mag, -z * mag, w * mag);
+  }
+
+  //! imaginary part accessor
+  inline Vec3 imag()
+  {
+    return Vec3(x, y, z);
+  }
+
+  // imaginary part
+  Real x;
+  Real y;
+  Real z;
+
+  // real part
+  Real w;
+};
+
+//! Multiplication operator
+inline Quaternion operator*(const Quaternion &q1, const Quaternion &q2)
+{
+  return Quaternion(q2.w * q1.x + q2.x * q1.w + q2.y * q1.z - q2.z * q1.y,
+                    q2.w * q1.y + q2.y * q1.w + q2.z * q1.x - q2.x * q1.z,
+                    q2.w * q1.z + q2.z * q1.w + q2.x * q1.y - q2.y * q1.x,
+                    q2.w * q1.w - q2.x * q1.x - q2.y * q1.y - q2.z * q1.z);
+}
+
+//! Multiplication operator
+inline Quaternion operator*(const Quaternion &q, const Real a)
+{
+  return Quaternion(q.x * a, q.y * a, q.z * a, q.w * a);
+}
+
+}  // namespace Manta
+
+#endif